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State of California
THE RESOURCES AGENCY
Department of Fish and Game
BIRD SPECIES OF SPECIAL CONCERN IN CALIFORNIA
AN ANNOTATED LIST OF DECLINING
OR VULNERABLE BIRD SPECIES
by
J. V. Remsen, Jr.
Western Field Ornithologists, Inc.
ABSTRACT
Information on status and range, causes of decline, potential threats and management needs is presented for 61 bird species of special concern in California. Species included are those whose breeding populations in the State have declined severely or are otherwise so low that extirpation is a real possibility. Species already on federal or California endangered, rare or threatened species lists, and species that have nested only casually in California, are excluded from the list. Species are grouped in three categories to provide guidance in setting priorities for expenditure of nongame research funds, acquisition of habitat, and other management actions.
Supported by Federal Aid in Wildlife Restoration, Project PR W_54_R_9, Nongame Wildlife Investigations, Wildlife Management Branch Administrative Report No. 78_1 (June 1978).
RECOMMENDATIONS
In addition to specific recommendations contained in the species accounts,
Western Field Ornithologists and the California Department of Fish and Game recommended the following:
- Give high priority to the following wildlife needs for habitat:
- Protect and restore 'riparian woodland throughout the state, but especially along the Colorado River and in the San Joaquin Valley. There is a particularly critical need to preserve riparian mesquite woodland.
- Maintain and restore permanent (as opposed to seasonal) fresh water marsh, especially in the lower San Joaquin Valley and along the central and southern California Coast.
- Create and maintain nesting islands for colonial waterbirds wherever feasible, but particularly at the Salton Sea, Hartson Reservoir, and Eagle Lake (Lassen Co.), at Mono Lake, and in the Klamath Basin.
- Initiate a cowbird control program to determine feasibility and effective_ ness in restoring host populations to non_threatened status.
- Determine the impact of starlings on cavity nesting species.
- Propose species of special concern that meet the criteria of endangered, rare, or threatened species to the California Fish and Game Commission and the U. S. Fish and Wildlife Service for inclusion on the appropriate lists.
- State and federal wildlife agencies, land management agencies and educational institutions give high priority to programs involving spe(!jes on this list when budgeting research and management funds.
- Maintain restrictions on use of persistent pesticides in California and encourage Rovernments elsewhere in the world to halt the use of DDT and other chlorinated hydrocarbon pesticides.
- Update the species of special concern list every two years to reflect new information concerning status, distribution and management needs.
INTRODUCTION
The following is a list of bird species whose California breeding populations (in most cases) are of special concern in that they may face extirpation. The danger may be immediate and the situation critical, or it may be rather remote but still a real possibility. The list is intended for use as a management tool. These species should be taken into special consideration when decisions are made concerning the future of any land parcel and when budgeting research and management funds.
The primary emphasis is on the status of the breeding population within California. A species may migrate through or winter in California in sub_stantial numbers, showing no signs of decline, but if the breeding population within the state has shown a severe decline, or is in a vulnerable situation, the species warrants inclusion on the special concern list (e.g., Common Loon, Marsh Hawk, Yellow Warbler). There are also species, abundant just outside California, whose worldwide population faces no threat, but whose population within California is so low that it is potentially vulnerable to extirpation (e.g., Vermilion Flycatcher, Black_capped Chickadee, Virginia's Warbler, Summer Tanager, Gray_headed Junco, etc.). The philosophy here is that the California breeding population is the primary concern, and the goal is to maintain diversity within ecosystems in California, regardless of a species' status elsewhere.
Some species on the special concern list at the extremes of their geographical distribution in California may be decreasing due to long_term climatic changes and thus may be on their way to vanishing from California regardless of conservation efforts. Yet, it is very difficult to determine if climatic change is the factor responsible for the decline, and the decline should not be accelerated by human activities, especially since climatic changes are often not unidirectional but may reverse direction at unpredictable times. There_ fore, a number of marginal species are included in the list.
Excluded from the list are the following: (1) those birds already on Federal and/or California endangered, threatened, or rare lists (i.e., California Brown Pelican, Aleutian Canada Goose, California Condor, Bald Eagle, American Peregrine Falcon, California Clapper Rail, Light_footed Clapper Rail, Yuma Clapper Rail, Black Rail, California Least Tern, California Yellow_billed Cuckoo, Elf Owl, Great Gray Owl, San Clemente Loggerhead Shrike, Least Bell's Vireo, Inyo Brown Towhee, Belding's Savannah Sparrow, San Clemente Sage Sparrow); (2) those species historically much more common than at present but whose current population levels are probably stable and high enough that extirpation is not a concern (e.g., several species of herons, geese, ducks, and shorebirds); (3) those species that may have very small total ranges or populations in California but that are primarily associated with man_made habitats (i.e., Inca Dove, Great_tailed Grackle, Bronzed Cowbird); (4) those species for which breeding in California must be regarded as an unusual event until consistent breeding is proven (e.g., Least Grebe, Canvasback, Hooded Merganser, Royal Tern, Chimney Swift, Eastern Kingbird, Northern Parula, American Redstart, Painted Redstart, Pyrrhuloxia). The list deals with subspecies only if they are highly threatened and warrant placement on the Highest Priority List.
LIST CATEGORIES
The species of special concern list is divided into three categories: Highest, Second, and Third priorities. These categories are defined on the basis of the urgency of the situation. Species in the Highest Priority category face immediate extirpation of their entire California population or their California breeding population if current trends continue. In several cases, extirpation as breeding species has already occurred. Species in the Second Priority category are definitely on the decline in a large portion of their range in California, but their populations are still sufficiently substantial that
danger is not immediate. Species in the Third Priority category are not in any present danger of extirpation and their populations within most of their range do not appear to be declining seriously; however, simply by virtue of their small populations in California, they are vulnerable to extirpation should a threat materialize.
Other species that were considered for inclusion on the Special Concern List are listed at the end of the species accounts given below. Further study is needed to determine the status of many of these species. Categorization of species is done regardless of land ownership status of important areas within the range; in many cases, a bird's presence in a "protected area" does not guarantee its well_being, as public lands frequently are managed primarily for human uses that conflict with the needs of wildlife.
SPECIES ACCOUNTS
The content of the species accounts is based upon (1) personal communications with many of the most active field observers in California and (2) a thorough, but by no means complete, literature search concentrating on three journals, Condor, Western Birds (formerly California Birds), and the nesting season reports in American Birds (formerly Audubon Field Notes). The cutoff time for inclusion of observations in the species accounts is the end of the 1977 nesting season.
For each species on the list, the following information is given:
Status and Range
A summary of historical and current distribution and population status within California is given in a very general way. Detailed discussion of distribution and status is beyond the scope of this report.
Reasons for the decline
The reasons for the population decline are discussed. In most cases the exact reasons are not well_known or well_documented, and so the reasons given are mainly "best guesses" or speculation rather than established facts. For Third Priority species, this section is entitled Potential Threats, since in most cases no serious decline is apparent.
Recommendations
Suggestions for maintaining or improving population levels are given. Increasing our knowledge of the biology of the species on the list is not mentioned as a recommendation under each species, although this should be encouraged f r every species on the list.
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CALIFORNIA DEPARTMENT OF FISH AND GAME
BIRD SPECIES OF SPECIAL CONCERN LIST
HIGHEST PRIORITY LIST
COMMON LOON (Gavia immer)
Status and range: This species formerly bred on lakes above 5000 ft. in Shasta and Lassen counties; specific localities given in Grinnell and Miller (1944) are Snaggy Lake, Butte Lake, and Eagle Lake. This region was very poorly known at that time, so the actual number of breeding birds was almost certainly much greater. Today this species may no longer breed in California. The only recent report of possible breeding was of a pair at Twin Lakes, Mono Co. (Stalleup and Greenberg 1974b), but this area is too heavily used by humans to support successful breeding (T. Heindel, pers. comm.).
Reasons for the decline: Human disturbance at breeding sites, especially by boats, is the most likely reason for the decline. Ream (1976) found disturbance from canoeists to be the prime factor in the decline of a Minnesota population of Common Loons; the mere presence of canoes on breeding lakes keeps incubating birds away from nests, causing them either to desert entirely or leave the nest unguarded and more susceptible to predation.
Recommendations: (1) Survey lakes in former breeding range to look for breeding pairs, which are loud and conspicuous, requiring a minimum effort to be detected.
This survey could be combined with a survey for breeding Barrow's Goldeneyes, another Highest Priority species. Care must be taken to distinguish breeding birds from
late spring migrants or nonbreeding summering birds (often in nonbreeding plumage, seldom consistently vocal or persistently associating in pairs). (2) Close to boating during spring migration and breeding season any lake found to contain breeding pairs.
WHITE PELICAN (Pelecanus erythrorhynchos)
Status and range: At the turn of the century, this species nested on large lakes the entire length of California, but a decline was already underway in the 1920's both in numbers of breeding localities and populations within surviving colonies (Grinnell and Miller 1944). Today there are no remaining nesting colonies in California except along the Oregon border. No nesting has been recorded for many decades at former nesting colonies such as the Salton Sea (last nesting attempts in the late 1950's; Small 1956, 1957, 1959a), Tulare Lake, Buena Vista Lake, lower Sacramento Valley, and Eagle Lake. A large colony nested successfully in summer 1976 at Hartson Reservoir, Lassen Co., where they had not nested in at least a decade, but with reduced water levels in 1977, none returned to nest (A. Lapp, pers. comm.; Winter and Erickson 1976; ABF; Winter and Morlan 1977; Tait et al. 1978). Although thought to have disappeared from California as a breeding species (Small 1974), there is a population of 1700_6000 birds breeding in the Klamath Basin refuges, with Clear Lake National Wildlife Refuge supporting the majority (D. Winkler, pers. comm.). There are approximately 15 colonies of this species still in existence in the world with a total combined population of about 34,000 (Sloan 1973, Lies and Behle 1966).
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Reasons for the decline: Destruction of nesting islands and breeding habitat are probably the main reasons, although direct disturbance by humans may have contributed. At the Salton Sea, former nesting islands are now inundated by rising water levels, although much suitable feeding habitat still exists. At Tulare and Buena Vista lakes, the entire breeding habitat was destroyed when the lakes were drained. The possibility of pesticide contamination should also be monitored, although DDE levels in Utah pelican populations have not yet reached levels sufficient to effect reproductive success (Knopf and Street 1974).
Recommendations: (1) Maintain habitat integrity and water levels at breeding localities on the Klamath Basin refuges. (2) Manage Hartson Reservoir, Lassen Co., as a breeding sanctuary for White Pelicans and Double_crested Cormorants by maintaining water levels In the reservoir and eliminating human disturbance during breeding season. (3) Create artificial nesting islands at former breeding localities at Salton Sea and Eagle Lake to encourage recolonization. These areas often support nonbreeding, summering populations, possibly pre_ breeding age young, which may nest if sites are available. (4) Monitor population trends and reproductive success at existing colonies.
WHITE_FACED IBIS (Plegadis chihi)
Status and range: This species was once a locally common breeder the length of California. The center of abundance was in the San Joaquin Valley, but numbers also bred in northeastern California and the southern coastal area (Grinnell and Miller 1944). At least 200 nests were found in one marsh at San Jacinto Lake, Riverside Co. (Willett and Jay 1911) and a small breeding population was present in San Diego Co. (Sharp 1907). Now it is not known to breed regularly anywhere in California. As many as 20 birds often summer at Honey Lake Wildlife Area and are suspected of breeding (T. Manolis, pers. comm.), but no breeding was noted in 1977 (A. Lapp, pers. comm.). The last known breeding at Tule Lake occurred in 1965 (10 pairs; Ryder 1967). In 1977, 3_4 pairs bred at the Wister Unit of Imperial Wildlife Area at the Salton Sea, where no nesting has been recorded for nearly two decades (McCaskie 1977b; Ryder 1967; McCaskie 1966, 1968, 1969, 1970). The last known nesting attempt by any substantial numbers of ibis was in 1960 (100 pairs at the mouth of the Alamo River; Small 1960); as many as 1500 birds were reported in the summer at the Salton Sea as recently as 1962 (Small 1962), whereas only a few dozen birds have been reported in recent years (McCaskie 1974b, 1975c). The Los Banos area in Merced Co., once the stronghold of this species in California, no longer supports any breeding birds (J. Cawthon and L. Littlefield, pers. comms.). Thus, there has been a drastic decline in the numbers of this species in California, a trend already apparent by the 1940's (Grinnell and Miller 1944).
The wintering population of ibis in California is also declining. The southern coastal population in particular has been greatly depleted, especially in Orange Co. In the winter of 1976_77, fewer than 200 birds were reported in California, and these were all from just three localities; Los Banos Wildlife Area, Merced Co. (60, Winter and Erickson 1977; as many as 190 wintered here 5 years ago); Imperial Valiey (100+, McCaskie 1977); and near Oceanside, San Diego Co. (35, McCaskie 1977). A small population has recently been discovered wintering at the Point Mugu Gun Club, Ventura Go. (25, P. Lehman, pers. comm.).
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Reasons for the decline: Destruction of marsh habitat, especially along the southern coast and in the San Joaquin Valley, is perhaps the main factor responsible for the decline. This species prefers shallow, grassy marshes, and this type of wetland has disappeared from most of California. Furthermore, many wetlands are allowed to go dry during spring and summer for mosquito and cattail control. Perhaps DDE contamination and resultant eggshell thinning is also involved; the Bear River, Utah, population experienced disastrous eggshell thinning in the late 1960's (L. Kiff, pers. comm.), and there is reason to suspect that California populations were also contaminated. This species has vanished from remaining suitable breeding habitat in California, implying that factors other than habitat destruction are involved.
Recommendations: (1) In key areas, especially Honey Lake, Los Banos, and Imperial Wildlife areas and San Luis National Wildlife Refuge, allow some areas to remain wet and become overgrown with marsh vegetation. Shallow flooding of additional grassy areas will greatly benefit this species and other Special Concern species such as Fulvous Whistling_Duck, Marsh Hawk,
Least Bittern, Short_eared Owl, Sandhill Crane, and breeding waterbirds in general. (2) Acquire the San Jacinto Lakebed as a State Wildlife Area and restore breeding habitat for this species. As noted above, this area was once an important breeding area for White_faced Ibis.
FULVOUS WHISTLING_DUCK (Dendrocygna bicolor)
Status and range: This species formerly nested in the southern coastal area (Willett 1912), the San Joaquin Valley, and occasionally around the southern end of San Francisco Bay (Grinnell and Miller 1944). It is now completely extirpated from the southern coastal area and San Francisco Bay areas, and may also be gone from the San Joaquin Valley. Perhaps gone forever is tue situation described by Tyler (1913): "...a mile or. so above Dos Palos, these birds were really abundant, every little pond having two or three individuals and sometimes several little groups..."
In 1977, not a single bird was reported from this area of the San Joaquin Valley; the refuges in the area no longer have any nesting pairs (J. Cawthon, pers. comm.; L. Littlefield, pers. comm.; R. B. Reno, pers. comm.).
This species now breeds only in the Imperial Valley, but numbers are highly variable from year to year, and breeding is not reported to occur in some years (McCaskie 1975c). The breeding population has apparently declined, since observations of broods were much more frequent two decades ago (Pyle 1951, Small 1956) despite much more thorough coverage in recent years.
Reasons for the decline: Destruction of marsh habitat has probably been the main cause for the decline. However, there are areas of apparently suitable habitat remaining which lack Fulvous Whistling_Ducks, so other factors may be involved.
Recommendations: (1) Maintain habitat integrity in critical areas of the Imperial Valley such as Finney Lake, Ramer Lake and Wister Unit, Imperial Wildlife Area, and Unit 1 of Salton Sea National Wildlife Refuge, Imperial Co. (2) Manage wetlands in San Joaquin Valley so that marshes do not dry completely during spring and summer months (see White_faced Ibis). (3) Consider giving this species full protection from hunting. Although the bulk of the population migrates into Mexico before hunting season opens, hunters should be made aware of the critical status of this species in California.
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SWAINSON'S HAWK (Buteo swainsoni)
Status and range: The Swainson's Hawk was once an abundant breeding bird in California. It nested commonly throughout the nonforested lowlands from northeastern California south along the eastern edge of the Sierra Nevada to the Owens Valley, throughout the Sacramento and San Joaquin valleys, and along the southern coast from Ventura Go. to San Diego Co. (Grinnell and Miller 1944). Populations were also breeding in the Salinas Valley, the Santa Clara Valley, and some of the larger mountain meadows. Even by 1944, Grinnell and Miller reported that populations were greatly reduced, and this reduction has continued through the present until now the species is a scarce breeding bird in California, having suffered the most severe decline of any bird in the State except for the Bell's Vireo.
The coastal southern California population has been extirpated; no reports of breeding birds have been received in decades. The Salinas Valley and Santa Clara Valley populations have also disappeared. Very few birds have been reported from northeastern California in recent years, and most of the reports pertain to migrants (ABF). Only a few pairs remain in the San Joaquin Valley, and most of these are from Merced Co. north. It is extremely rare in the southern San Joaquin Valley. A nest at Mendota Pool in summer 1977 was one of the few located in recent years in Fresno Co. (R. Hansen, pers. comm.). The few pairs in the Cima Dome area, San Bernardino Co., at this species' southeastern limit in California (Johnson, Bryant, and Miller 1948), have disappeared in the last three years (Remsen, Cardiff, and Cardiff, MS). The largest known population remaining in the state is located in the Davis_ Woodland_Sacramento area of the Sacramento Valley where five to six nests have been reported per summer in the last few years (ABF). Smaller numbers have been reported north into Glenn and Butte Co. At least five pairs were present in the Chico area in 1977 (S. Laymon, pers. comm.).
Paralleling the decline in breeding birds, reports of migrants have diminished greatly in recent decades. The last report of a flock of over 100 birds (formerly a regular occurrence) in northern California was in 1968 (ABF), despite more thorough coverage of the Central Valley in the last ten years. In southern California, flocks of 100_600 were reported regularly as late as the early 1950's, but groups of ten or more have been reported only rarely since then (J. Dunn, pers. comm.). For example, 470 were counted at the southeastern edge of the San Gabriel Mountains on 3 April 1951, 520 the next day, and 51 three days later (Small and Pyle 1951); in the Imperial Valley, 62 were counted on 29 October 1951 (Small and Pyle 1952) where even single birds are rarely found now. In the Santa Barbara region, this species used to be a fairly regular migrant, but now an average of less than one bird per year is reported (P. Lehman, pers. comm.) despite much more thorough coverage. At Escondido in San Diego Co., where once a "not uncommon" breeding bird, occasionally "great flocks" were seen in migration (Sharpe 1907). Now this species is seldom reported from coastal San Diego Co.
Reasons for the decline: Conversion of the Central Valley and other grassland areas from pastureland to cropland has probably been a major factor in the population decline. However, other unknown factors such as possible pesticide contamination and habitat deterioration on the South American wintering grounds may be more important. Human disturbance at nest sites and shooting have also contributed to the decline in numbers of this species.
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Recommendations: (1) Protect existing pastureland and grassland in the Central Valley and manage to maximize suitability for this species. (2) Inform farmers of the highly beneficial value of this species to insure protection of nest sites. (3) Monitor productivity of remaining nesting pairs, but avoid disturbance to nesting birds.
HARRIS' HAWK (Parabuteo unicinctus)
Status and range: The Harris' Hawk no longer breeds in California. This species was formerly a locally common permanent resident in the lower Colorado River Valley, north to Blythe, as well as in the Imperial Valley (Grinnell and Miller 1944, Small 1974). There have been virtually no reports from the Colorado River in the last 15 years. The last unquestionable record was of a bird north of Blythe in November 1964 (Snider 1965). It is virtually certain that no breeding birds remain. From Audubon Field Notes, it appears there was a sudden drop_off In bird populations in the Colorado River Valley beginning in about 1959 (J. Dunn, pers. comm.). This species is gone from the Imperial Valley, where no nests have been reported in 25 years, except for an unsuccessful attempt by a pair released at Wister, Imperial Wildlife Area, Imperial Co., after being confiscated from falconers (McCaskie 1976b). All recent reports from California are regarded as birds which have escaped from or been released by falconers.
Reasons for the decline: Falconry has almost certainly played a major role in the decline of the Harris' Hawk, which is highly coveted by falconers. A falconer once told this writer that after they had completely depleted Colorado River populations, falconers made trips to Arizona, Texas and even Mexico to obtain birds, and would smuggle them illegally into California and register them with the Department of Fish and Game as having been taken in California. Although habitat destruction along the Colorado River and Imperial Valley has been extensive and has certainly been a factor in the decline, the Harris' Hawk does not require extensive riparian woodland, and presumably small populations could nest in remaining brushlands adjacent to agricultural areas.
Although pesticide residues have been found in Harris' Hawks eggs in Arizona, they have not r ached levels high enough to affect reproductive success (Mader 1977).
Recommendations: (1) Reintroduce Harris' Hawks produced by captive raptor breeding projects, as well as any confiscated or rehabilitated birds that are releasable, into suitable breeding habitat in the Colorado River and Imperial valleys. These birds should be banded for easy field recognition so that released birds can be distinguished from truly wild individuals for population monitoring. (2) Protect and restore mesquite brushland adjacent to riparian areas in the Colorado River and Imperial valleys. (3) Review regulations, and procedures governing importation of this species from outside California. Prohibit importation unless the documentation obtained by the importer from the state or country granting the export permit is adequate to ensure that "imported" birds are not actually taken illegally in California.
MERLIN (Falco columbarius)
Status and range: The Merlin is the only species on the Special Concern List which is not known to breed in California. This species used to be a fairly common to common winter visitant and
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migrant in California (Willett 1912, Grinnell and Miller 1944), but has declined drastically in the last two decades. The total number of winter reports in recent years has dropped to only six to ten birds in southern California (McCaskie 1973c, 1974c, 1975b, 1976c, 1977a) and 20_30 in northern California (Stallcup and Winter 1975b; Stallcup and Winter 1976b); extremely low totals in comparison to those of earlier years. The Merlin occurs as a transient throughout most of California, but wintering birds are concentrated along the coast and in the Central Valley (ABF).
Populations throughout the United States and Canada have declined drastically, paralleling the decline of the Peregrine Falcon. This species may be a candidate for the Federal endangered species list, in light of the similarity in trends between the Merlin and the Peregrine Falcon and the recent findings concerning massive reproductive failure of Merlins in Canada (Fox 1971).
Reasons for the decline: Reproductive failure due to DDE contamination has been shown to be widespread in populations of the subspecies richardsonii in central Canada (Fox 1971). Legal take of juveniles from the wild is taking those birds potentially able to reproduce successfully in the wild in the pesticide era.
Recommendations: (1) Maintain restrictions on use of persistent pesticides in United States. (2) Encourage federal government to work through diplomatic channels to seek ban on persistent pesticide use on wintering areas in Central and South America. (3) Conduct survey to determine current status of this species in California and consider moratorium on take for falconry pending determination of status.
SHARP_TAILED GROUSE (Pedioecetes phasianellus)
Status and range: The Sharp_tailed Grouse has been extirpated from California. According to Grinnell and Miller (1944), this species was a resident in Modoc Co. southwest into northwestern Lassen Co. and Shasta Co., abundant up to about 1880, but rapidly declining thereafter. There have been no reports of birds since about 1915.
Reasons for the decline: Destruction of grassland habitat in northeastern California by agriculture and overgrazing combined with possible over_hunting were probably the main factors leading to the disappearance of this species.
Recommendations: (1) Consult with a game_bird specialist familiar with the requirements of this species and survey northeastern California to determine if suitable habitat still exists. (2) If suitable habitat is available or can be restored, reintroduce the subspecies P. p. columbianus to suitable areas within its former range in California.
YELLOW RAIL (Coturnicops noveboracensis)
Status and range: The Yellow Rail perhaps no longer breeds in California. Small numbers bred in grassy meadows in Mono Go., and probably in Plumas Co. and along the eastern edge of the Sierra Nevada (Grinnell and Miller 1944). This species is so difficult to detect that it was almost
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certainly more widespread than historical records indicate, and some may still persist in California, although recent thorough searches of some former breeding localities have not been successful (Stallcup and Winter 1975c; T. Heindel, pers. coun.). Prior to 1944, winter records of 35 individuals were obtained from 16 localities along the coast from Humboldt Co. to Orange Co. and inland in Merced Co. and Riverside Co. (Grinnell and Miller 1944). This is an impressive number of records for this extremely secretive species, indicating a substantial wintering population. Since 1944, however, very few records have been obtained.
Reasons for the decline: Grazing of the wet grassy meadows may be the primary reason for the decline of the breeding population (Stallcup and Winter 1975c). Ungrazed meadows in the former breeding range are almost nonexistent (T. Heindel, pers. comm.; D. Gaines, pers. comm.). Although coastal marshes and inland marshes have greatly declined, there is still suitable habitat. The decline of the wintering population may be related to the decline on the breeding grounds.
Recommendations: (1) Using tape_recorded calls, survey former breeding sites in Mono County (Bridgeport Valley and Long Valley) and other similar localities along the eastern edge of the Sierra Nevada during the nesting season. (2) If Yellow Rails are found, maintain these sites free from grazing and human disturbance. (3) Maintain habitat integrity of coastal marshes, especially those around San Francisco Bay, which were apparently major wintering areas.
LAUGHING GULL (Larus atricilla)
Status and range: Once a regular nester at the Salton Sea, the Laughing Gull has now disappeared from California as a breeding species. Although the data are incomplete, it appears that this species nested annually at the south end of the Salton Sea until at least 1957 (Pyle 1951; Small 1952, 1956, 1957), and possibly intermittently until 1965 (J. Dunn, pers. comm.).
Reasons for the decline: Loss of nesting habitat by the rising water level of the Salton Sea has probably been the major reason for the decline.
Recommendations: (1) Restore Laughing Gull nesting habitat at the Salton Sea. (2) Maintain habitat integrity of marshes at the Salton Sea.
GILDED COMMON FLICKER (Colaptes auratus mearnsi)
Status and range: This race of the Common Flicker, formerly considered a separate species, once was fairly common along the Colorado River Valley in California between Needles and the Mexican border, especially in saguaro cactus groves (Grinnell and Miller 1944; Grinnell 1914). A small population was also found in the Joshua Tree Woodland of Cima Dome, San Bernardino Co. (Johnson, Bryant, and Miller 1948; McCaskie 1973a). Today this form is very rarely reported along the Colorado River and may have vanished as a breeding bird. The Bill Williams River Delta on the Arizona side may be the only locality where this species still nests in the Colorado River Valley (D. Gaines, pers. comm.). The Cima Dome population is down to one or two pairs and is in danger of genetic swamping from hybridization with the Red_ shafted form (Remsen, Cardiff, and Cardiff, MS).
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Reasons for the decline: Destruction of riparian woodland and saguaros in the Colorado River Valley is undoubtedly the main reason for the decline. Perhaps nest site competition with Starlings is also a factor. Overgrazing on Cima Dome may be partly responsible for the decline in that area, although hybridization with invading Red_shafted types is currently the major threat.
Recommendations: (1) Protect existing riparian habitat and saguaros along the Colorado River. (2) Acquire land suitable for restoration of cottonwood riparian habitat along the Colorado River. Cottonwoods and willows are easily planted and fast growing, and perhaps suitable habitat could be restored in a relatively short time. Considering the number of Special Concern species that would benefit from such habitat restoration and the scarcity of riparian vegetation along the Colorado River, this type of project would benefit the following: Elf Owl, Bell's Vireo, Yellow Warbler, Yellow_breasted Chat, Summer Tanager, Wied's Crested Flycatcher, Gila Wood_pecker, Cooper's Hawk, and to some extent Harris' Hawk, Vermilion Flycatcher, and Crissal Thrasher. (3) Maintain habitat integrity of Joshua Tree Woodland of Cima Dome, the largest stand of Joshua trees in the world. (4) Determine impact of nest site competition with Starlings in Colorado River Valley.
WILLOW FLYCATCHER (Empidonax traillii)
Status and range: Once a breeding bird throughout much of California, common in suitable habitat (Grinnell and Miller 1944), this species has undergone a drastic population decline in recent decades and has been extirpated from most of its range, surviving only in the Sierra. This species was formerly locally common in riparian woodlands of the Central Valley. Goldman (1908) found it to be "rather common" in willow thickets along the Kings River in the southern San Joaquin Valley and Linton (1908) called it a common breeder in the vicinity of Buena Vista Lake. Today it has apparently been extirpated from all known localities in the Central Valley (D. Gaines, pers. comm.; R. Hansen, pers. comm.). This species is no longer known to breed in the southern coastal area (McCaskie 1975c; J. Dunn, pers. comm.) where it was once a common summer resident (Willett 1912). Populations along the central coast, never high to begin with, are now extremely low or nonexistent. Barlow (1900) found this species "breeding commonly along the creeks flowing into San Francisco Bay" where today it is unknown as a breeding bird. Even populations in the Sierra have shown dramatic declines. Gaines (1977) states this species has nearly vanished from Yosemite Valley and is alarmingly scarce elsewhere in the Yosemite region.
Reasons for the decline: Although destruction of willow riparian woodland has undoubtedly played a role in the decline of this species (Stallcup and Winter 1975a), the absence of the Willow Flycatcher from remaining suitable habitat plus their decline in the Sierra Nevada where habitat is still intact, indicates something else is amiss. Cowbird parasitism, convincingly implicated in the decline of Bell's Vireo and Yellow Warbler, is almost certainly involved (Gaines 1974, 1977).
Recommendations: (1) Initiate cowbird removal programs on an experimental basis in selected riparian areas to determine if cowbirds can be controlled on a local level (see Bell's Vireo below). (2) Protect willow riparian woodland throughout California, especially in the Sacramento and San Joaquin valleys, and along the southern California coast. The Carmel River mouth, one of the only areas on the central coast where breeding has been reported in recent years (Stallcup and Greenberg 1974b), should also receive special attention.
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VERMILION FLYCATCHER (Pyrocephalus rubinus)
Status and range: Formerly fairly common the entire length of the Colorado River in California and also in the Imperial and Coachella valleys (Grinnell and Miller 1944, Hollister 1908, Grinnell
1914), this species has now disappeared as a breeding bird from most of its breeding range. A few pairs may still breed along the Colorado River, although none were observed anywhere
on the California side in surveys of the area in 1977 (D. Gaines, pers. comm.). A decline in the population had already been noted by the 1950's (Monson 1950, 1958, 1959). This species apparently no longer nests in the Coachella Valley or Imperial Valley (J. Dunn, pers. comm.). A population present in the San Diego area primarily in the 1950's has since disappeared. The last nesting reports were in 1969 (McCaskie 1969), although as many as 24 young were fledged at a single locality in 1960 (Small 1960). At present, there are only three localities with breeding populations: Morongo Valley, San Bernardino Co., where the small population has declined to but a single pair (McCaskie 1974b); Mojave Narrows Regional Park, San Bernardino Co. (D. Gaines, pers. comm.); and near Castaic along the Santa Clara River, Los Angeles Co. (McCaskie 1970; R. Webster fide J.lDunn). Current status of the latter population is unknown.
Reasons for the decline: A significant factor in the decline may be the destruction of cottonwood riparian woodland and groves in most of its range. In the Coachella and imperial valleys, destruction of artesian oases when the water table was lowered has played a significant role (E. A. Cardiff, pers. comm.). Cowbird parasitism may also be involved.
Recommendations: (1) Protect cottonwood riparian woodland along the Colorado River, especially where adjacent to pastures or alfalfa fields. (2) Protect cottonwood groves and oases in the Coachella and Imperial valleys. (3) Acquire land suitable for restoration of riparian woodland along the Colorado River (see Gilded Flicker above). (4) Maintain habitat integrity at Morongo Valley and Mojave Narrows Regional Park. (5) Survey Santa Clara River near Castaic for Vermilion Flycatchers.
ARIZONA BELL'S VIREO (Vireo bellii arizonae)
Status and range: The catastrophic decline of the Bell's Vireo is unparalleled in the ornithological history of California. Two races breed in the state. The Least Bell's Vireo (V. b. pusillus was added to the state endangered species list in 1980. The race arizonae once bred commonly throughout the Colorado River Valley in California (Grinnell and Miller 1944) and was considered "one of the most characteristic avifaunal elements of the riparian strip" (Grinnell 1914). By the 1950's, the population was greatly reduced (Monson 1960) aad it is now almost gone from the California side of the river.
Reasons for the decline: Although destruction of riparian habitat probably is partly responsible for the decline, the present critical status of this species in California is almost certainly due to brood parasitism by the Brown_headed Cowbird. Many areas formerly supporting this species still have suitable habitat but Bell's Vireos are absent (Gaines 1974). The rate of decline of the Bell's Vireo and several other favored cowbird hosts in lowland riparian areas (see Willow Flycatcher, Yellow Warbler, and Yellow_breasted Chat) coincides with the spectacular increase in numbers of the Brown_headed Cowbird in California (Grinnell and Miller 1944, Gaines 1974). Cowbird parasitism
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can have severe detrimental effects on a bird population (Mayfield 1977). Destruction of willow_cottonwood riparian woodland may have been significant in reducing populations below levels capable of withstanding increasing cowbird densities.
Recommendations: (1) Add the Arizona Bell's Vireo to the Federal and State endangered species lists, and designate critical habitat at all localities where Bell's Vireos are present during the nesting season. (2) Initiate cowbird removal programs on an experimental basis during the breeding season at Bell's Vireo nesting localities. Cowbird removal programs in Michigan have been very successful in maintaining populations of the endangered Kirtland's Warbler (Mayfield 1977). (3) Protect riparian areas and adjacent mesquite woodland in the Colorado River Valley.
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SECOND PRIORITY LIST
FORK_TAILED STORM_PETREL (Oceanodroma furcata)
Status and range: Lack of thorough, quantified surveys in the past prevents accurate assessment of population trends, but this species has disappeared from three breeding sites known to be occupied in California in earlier years (Harris 1974). Recent surveys of known and potential breeding sites in Del Norte and Humboldt counties indicate fewer than 200 pairs now breeding in California (Osborne 1971; Ainley and Whitt 1973; Harris 1974). Over half of the California population breeds on Little River Rock, Humboldt Co., the southernmost known breeding locality for this species.
This species has definitely become much rarer offshore in the last 15 years, perhaps reflecting a decline on the breeding grounds.
Reasons for the decline: Erosion of precious soil on nesting islands, resulting from human visitation by boat or on foot at low tide, is one probable reason for the decline. "This habitat destruction will soon lead to the birds' disappearance unless people are kept off the rocks. The erosion during the winter is greatly inceased when there have been people on the rookery" (Osborne 1971). Although chances of accidental introduction of cats or rats from small boats
are very small, these cavity nesting birds are extremely vulnerable to terrestrial predators. Human disturbance at one former nesting site eliminated the local breeding population (Harris 1974). Perhaps cyclic changes in ocean temperatures are partly responsible, especially for the decline of offshore storm_petrel sightings. Increasing populations of cormorants and murres nesting at some breeding sites have resulted in increased soil erosion and reduced burrow availability for this species (S. Harris, pers. comm.).
Recommendations: (1) Maintain nesting islands free from human disturbance, especially the three major breeding sites: Little River Rock and Green Rock in Humboldt Co. and Castle Island in Del Norte Co. (2) Prohibit boat landings (except by authorized personnel) at these islands at any time of year. (3) Prohibit human access by foot at low tide to breeding sites. (4) Consider discouraging cormorants and murres from nesting in the microhabitat used by the petrels.
DOUBLE_CRESTED CORMORANT (Phalacrocorax auritus)
Status and range: The Double_crested Cormorant formerly bred on coastal cliffs and offshore islands along the coast from Marin Co. south to La Jolla, San Diego Co., and in the interior in northeastern California, the Sacramento Valley, the San Joaquin Valley, and the Salton Sea (Grinnell and Miller 1944). Recent surveys have revealed breeding populations from Marin Co. north to the Oregon border Chandik and Baldridge 1969; Osborne 1971). This species also nests along the Colorado River, but nesting sites are on the Arizona side of the river (Monson 1949). Now it has disappeared as a breeding bird from the Sacramento and San Joaquin valleys and the Salton Sea. Tulare Lake in the San Joaquin Valley, where hundreds of nests were located by Goldman (1908), is now unsuitable as nesting habitat. Similarly, Buena Vista Lake, where this species once bred in "immense numbers" (Linton 1908), is no longer suitable. No nests have been noted at the Salton Sea in many years, although 100 nests were present in one rookery alone
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as recently as 1956 (Small 1956). Coastal breeding populations have also declined in southern and central California. This species no longer nests in San Diego Co. (P. Unitt, pers. comm.), and populations on the Farallon Islands once numbered in the thousands in the 19th century but were reduced to 20_40 pairs by the early 20th century. Historical trends in the breeding population in northeastern California are not known, but D. Winkler (pers. comm.) estimates the total breeding population in the Klamath refuges not to exceed 200 pairs. A small breeding population exists at Butt Lake, Plumas Co. (K.S. Kahre, pers. comm.). The breeding population at Hartson Reservoir at Honey Lake, Lassen Co., seems to fluctuate greatly; the count in 1966 was 20 pairs (A. Lapp, pers. comm.), 150 in 1976 (Winter and Erickson 1976), and zero in 1977 (A. Lapp, pers. comm.).
Some additional current population estimates are: coastal Del Norte and Humboldt counties, 263 pairs (Osborne 1971) and 120 pairs (Ainley and Whitt 1973); near Jenner, Sonoma Co., 12 pairs in 1976 and 30 pairs in 1977 (ABF); Farallon Islands, 40 pairs in 1972 (Ainley and Lewis 1974); Pfeiffer Burns State Park, Monterey Co., one pair (Chandik and Baldridge 1969); Prince Is., off San Miguel Is., 60 pairs; Anacapa Is., seven pairs; Sutil Is., off Santa Barbara Is., 30 pairs; Santa Barbara Is., ten pairs (1977 Channel Is. data courtesy H. L. Jones); Eagle Lake, Lassen Co., 11_12 pairs in 1974_75 (Stallcup and Greenburg 1974b; Lederer 1976) but zero in 1977 (D. Winkler, pers. comm.); Bridgeport Res., Mono Co., six pairs in 1974 (Stallcup and Greenberg 1974b) but zero in 1977 (D. Winkler, pers. comm.); and Black Point Cutoff, Solano Co., 43 nests in 1975 but zero in 1977 (ABF).
This species has been declining in much of its North American range. It has also declined along the western coast of Baja, California and within the Gulf of California (D. G. Ainley, pers. comm.).
Reasons for the decline: Habitat destruction and human disturbance, particularly from boating (Lederer 1976), appear to be the main causes for the decline of the inland populations. The Channel Islands' populations have declined due to eggshell thinning from DDE contamination and to some extent human disturbance at nest sites (Gress et al. 1973). For instance, the Anacapa Is. population experienced complete reproductive failure in 1971 when the population was at least 48 pairs (note 1977 estimate of seven pairs). To what extent inland populations, most of which winter in coastal waters, are affected by pesticide residues is unknown. The Farallon Islands population has declined to its current level due to a combination of human disturbance at nest sites, and disappearance of sardine populations (Ainley and Lewis 1974). Cormorants are particularly valuable to human disturbance at nest sites (Ainley and Lewis 1974; Kurv and Gochfeld 1975).
Recommendations: (1) Maintain ban on the use of persistent pesticides. (2) Eliminate boating and other human disturbance in vicinity of nesting colonies during the breeding season. (3) Maintain habitat integrity at inland breeding areas, with particular attention to maintaining a constant water level in reservoirs.
MARSH HAWK (Circus cyaneus)
Status and range: This species has greatly declined in California as a breeding bird, the decline being already conspicuous by the 1940's (Grinnell and Miller 1944). it used to be a common resident in the southern coastal area (Willett 1912). At present, nesting localities are still scattered
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throughout the state, but numbers are much reduced, particularly in the southern coastal area, around San Francisco Bay, and in the Mono Lake area (Gaines 1977). Numbers in the Santa Clara Valley have also diminished (Chandik and Baldridge 1969), and Sacramento Valley populations are much depleted from former levels (D. Gaines, pers. comm.). The bulk of the breeding population is concentrated in ungrazed portions of state and federal wildlife refuges. Some current estimates are as follows: Mendota Wildlife Area, five pairs (R. B. Reno, pers. comm.); Merced National Wildlife Refuge, four pairs (L. Littlefield, pers. comm.); San Luis National Wildlife Refuge, 15 pairs (I.. Littlefield, pers. comm.); Los Banos Wildlife Area, 25 pairs (J. Cawthon, pers. comm.). Sacramento National Wildlife Refuge, one to two pairs (S. Laymon, pers. comm.); Gray Lodge Wildlife Area, 10_15 pairs (J. Cowan, pers. comm.); Honey Lake Wildlife Area, six pairs A. Lapp, pers. comm.); and Klamath Basin refuges, considered "very abundant" M. Taylor (pers. comm.).
Wintering populations are much larger, but these have also declined. There was a steady decrease in Marsh Hawk numbers from the early 1950's until about 1965 and then a very slight increase through 1969, but numbers are still below 1953 levels (Brown 1973). There actually may have been a steady decline from the early part of the century as indicated by Tyler (1913) for the Fresno area: "Formerly this hawk was an abundant winter visitant over the lowlands almost everywhere in the valley, but like nearly all the birds of prey, it seems unable to withstand the onward march of civilization. It has been much reduced in numbers throughout the region and has completely disappeared from some of the more thickly settled areas."
Reasons for the decline: Destruction of marsh habitat is undoubtedly the major reason for the decline. Grazing has certainly had an adverse effect on populations nesting in grasslands.
Recommendations: (1) Protect marsh habitat throughout California, as well as suitable grasslands in the lowlands. Grazing in and around marsh borders should be eliminated in late winter and spring to protect the nest sites of this ground nester. (2) Manage wetlands in the Central Valley to maintain marshes during spring and summer months.
OSPREY (Pandion haliaetus)
Status and range: Formerly a breeding bird throughout much of California, this species had declined by the 1940's (Grinnell and Miller 1944) and is now found mainly in a few areas in northern California. The remaining areas have almost certainly always been the center of abundance for this species in the state. The Osprey has vanished as a nesting species almost completely from southern California, including the Channel Islands. The only known nest sites today are Lake Casitas, Ventura Co. (McCaskie 1974b) and Tinnemaha Res., Owens Valley, Inyo Co., (McCaskie 1974b, 1976b; which has not been successful (T. Heindel, pers. comm.). In northern California, there still are healthy populations just inland from the coast from Sonoma Co. north and in Shasta, Lassen, and Plumas counties. Small numbers are found elsewhere along the northern edge of the state. Major nesting areas irclude Eagle Lake (52_58 pairs; Lederer 1976, Garber 1972); Klamath Natl. Fcrest, Siskiyou Co. (14 pairs; Winter and Erickson 1976b); Humboldt Redwo& s State Park (five pairs; ABF); Duncan Mills, Sonoma Co. (three to four pairs; ABF); and Kent Lake, Marin Co. (12 pairs; G. Gould, pers. comm.).
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Overall reproductive rates (despite high egg failure rates) in Lassen and Plumas counties show no apparent signs of failure due to pesticide contamination (Garber 1972). However, in view of this species' dramatic decline in the eastern United States in the 1960's due to DDE contamination (Schmid 1966, Ames and Wiemeyer 1971, Mersereau 1964, Ames 1966, Henny and Ogden 1970,
Rees 1970, 1977), California populations must be treated as highly vulnerable.
Ospreys have been seen through the summer months at such former or potential nesting areas as West Pond (Imperial Dam), Salton Sea, Newport Bay, Buena Vista Lagoon (San Diego Co.), Big Bear Lake, and Lake Cachuma (Santa Barbara Co.), and perhaps might be induced to breed if suitable nest sites were available.
Reasons for the decline: Removal of nesting trees, degradation of river and lake environmental quality, boating on nesting lakes, and shooting must all be in part responsible for the decline. Southern California populations had disappeared long before the pesticide era (11. L. Jones, pers. comm.). Egg failure rates of 50% (1970) and 28% (1971) in Lassen and Plumas counties suggests that pesticide contamination may be present (Garber 1972).
Recommendations: (1) Maintain restrictions on use of persistent pesticides in the United States. (2) Protect nesting trees, many of which are dead and thus susceptible to tree removal operations. (3) Where needed, restrict boating during breeding season on lakes fished by Ospreys. (4) Provide man_made nesting sites (Valentine 1967; Kahl 1971, 1972) to attempt to restore Osprey populations in the southern portion of the range.
SNOWY PLOVER (Charadrius alexandrinus)
Status and range: Information on population trends of the Snowy Plover in California is scant. Grinnell and Miller (1944) had already detected a decrease in abundance by the 1940's. Recent surveys along the coast of northern California between Marin Co. and the Oregon border documented fewer than 100 pairs (PRBO Newsletter No. 42, 1977). In Santa Cruz Co., only two breeding localities remain: the mouth of the Pajaro River, and Wilder Beach, which is still closed to the public. Former Santa Cruz Co. breeding areas such as Waddell Beach, Twin Lakes Beach, and probably many others are no longer used due to heavy human disturbance (R. Morgan, pers. comm.). In the Santa Barbara area, this species now summers only very locally, with most of the birds (about 20) present at McGrath State Beach, Ventura Co. (P. Lehman, pers. comm.). In northern San Diego County, this species has become rare as a breeder due to heavy human use of the beaches, particularly by dune buggies and motorbikes (A. Fries, pers. comm.). Populations in south San Francisco Bay seem to be doing well, nesting on dikes in salt ponds, and may number 150 pairs (Gill 1977). Populations on the Channel Islands, where disturbance on beach nesting areas is minimal, are doing very well (H. L. Jones, pers. comm.).
Large numbers have been found inland at Mono Lake, Mono Co. (17 pairs, Gaines 1977; 80 birds, PRBO Newsletter No. 42, 1977) and Owens Lake, Inyo Co. (130 birds, McCaskie 1975c). Small breeding populations have also been found elsewhere inland at Tecopa, Inyo Co. (McCaskie 1975c), Deep Springs, Inyo Co. (McCaskie and Pugh 1964), Lake Elsinore, Riverside Co. (McCaskie 1974b), and Salton City, Imperial Co. (G. McCaskie, pers. comm.). This species has
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also on occasion nested in the Central Valley and might do so regularly if there were more suitable habitat available. A pair bred at Woodland, Yolo Co., in 1963 (DeBenedictis and Chase 1963) and 1970 (Baldridge et al. 1970).
Reasons for the decline: Human harassment and direct destruction of nest sites and breeding habitat are reasons for its decline. Wherever these birds are left undisturbed in suitable habitat, such as on the Channel Islands, they prosper. The recent Point Reyes Bird Observatory survey found that almost every beach with suitable nesting habitat, no matter how remote, showed signs of dune buggy use. An instance of deliberate harassment by dune buggy enthusiasts was recorded. The chicks have a tendency to crouch in vehicle tracks in the sand for cover. (PRBO Newsletter, op. cit.).
Recommendations: (1) Eliminate vehicles from critical nesting areas. (2) In areas of heavy human use on nesting beaches, restrict human and dog access to sections of suitable habitat to create refugia nesting birds.
GULL-BILLED TERN (Gelochelidon nilotica)
Status and range: This species colonized California as a breeding ird when the Salton Sea was formed in the early part of this century. The size of the breeding population declined from 500 pairs in the first survey in 1927 to fewer than 200 pairs in 1937 (Grinnell and Miller 1944) and 60 pairs in 1952 (Small 1952). Seventy-five pairs were counted in 1957 (Small 1957), 40-50 pairs in 1959 (Small 1959a, 1959b), and only a few pairs through most of the 1960's (Small 1961, Pugh 1965, McCaskie 1968, 1970, 1971). In 1976, 17 pairs nested (McCaskie 1976b) and perhaps twice this number may have nested in 1977 (J. Dunn, pers. Comm.).
Reasons for the decline: Rising water levels inundating nesting islands and beaches and adjacent marsh habitat has probably been the major cause of the decline. In an area such as the Imperial Valley, where pesticides are liberally applied, pesticide contamination is a possibility.
Recommendation: Create and maintain artificial nesting islands for this species around the souther and northen shores of the Salton Sea, using specifications given by Grant and Hogg (1978). The presence of just a few suitable nesting islands would most likely allow this species to persist in California.
TUFTED PUFFIN (Lunda cirrhata)
Status and range: The Tufted Puffin once bred along the coast of California as far south as the Channel Islands and was known to breed along a number of coastal cliffs as well as offshore islands (Grinnell and Miller 1944). Now this species is no longer known to nest in souther California. It was once a common breeding bird on San Miguel Is., Anacapa Is., and probably Santa Barbara Is., with a total population of at least 75 pairs in 1900; but none have bred since 1915 (H.L. Jones, pers. Comm.). Numbers in northern California have also declined. The population on the Farallons declined from "several thousand" birds in 1911 to only 30-35 pairs in recent years (Ainley and Lewis 1974, Ainley and Whitt 1973). Only one pair now nests on Flatiron Rock, Humboldt Co., where as many as 24 pairs may have nested at one time (Osborne 1971).
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The only other current nesting localities south of Humboldt Co. are Arch Rock, Sonoma Co. (one or two pairs; B.D. Parmeter, pers. comm.), and Piedras Blancas, San Luis Obispo Co. (one pair; Osborne 1971). One or two pairs are suspected to breed at Chimney Rock, Point Reyes Natl. Seashore (Winter and Morlan 1977) and at Pedro Point, San Mateo Co. (ABF). Thus the total population breeding in California may be as low as 74 pairs, 60 of which are found at two localities: the Farallons and Castle Rock, Del Norte Co.
Reasons for the decline: Decline of sardine populations may be the main factor causing the decline (Ainley and Lewis 1974), although oil pollution (D. G. Ainley, pers. comm.) and disturbance by humans at nest sites may have affected puffins at some localities. A major oil spill near a nesting site could have severe consequences for this species as well as several other Special Concern species. Populations on the Farallons have begun to increase now that European hare populations have been eliminated (R. Stallcup, pers. comm.).
Recommendations: (1) Eliminate human disturbance and oil drilling at or near nesting sites. (2) Prohibit boat landings on islands where nesting occurs, except by authorized persons.
BURROWING OWL (Athene cunicularia)
Status and range: This species was formerly a common, even locally abundant, permanent resident throughout much of California, but a decline noticeable by the 1940's (Grinnell and Miller 1944) has continued through to the present time. The decline has been almost universal throughout California. Virtually every observer has expressed concern for the future of this species in his area. There have been no records in northern Napa Co. for 15 years (E. W. Tillay, pers. comm.). There has been a steady decline in numbers reported in Sonoma Co. in recent decades (B. D. Parmeter, pers. comm.). They continue to decline in eastern Alameda Co. and are decreasing in Palo Alto (Stallcup and Greenberg 1974a, 1974b). In the Stockton area, known populations consisting of at least 17 pairs have dwindled to no more than three pairs in the last ten years (D. M. Shanks, pers. comm.). Numbers are decreasing in the Fresno area (R. Hansen, pers. comm.). In Tulare Co., it is estimated that there has been a 70% re_ duction in suitable habitat in just the last ten years (R. A. Barnes, pers. comm.). It is nearly extinct in San Mateo Co. (ABF), and has greatly declined in Santa Cruz Co. where it was a common bird in the early part of this century (R. Morgan, pers. coum.). Numbers have gone way down in the Santa Barbara region (P. Lehman, pers. comm.), and in the Los Angeles region (A. Small, pers. comm.) where once a common resident (Willett 1912). Its numbers have also declined in San Diego Co. (A. Fries, J. Dunn, pers. comm.) It was described as ficommon everywhere" in the Escondido area in the early part of this century (Sharp 1907).
As with the Marsh Hawk, the stronghold of this species may be the state and federal wildlife refuges. The population at San Luis National Wildlife Refuge is estimated to be 25 pairs (L. Littlefield, pers. comm.) and at Mendota Wildlife Area, 30 pairs (R. B. Reno, pers. comm.)
Reasons for the decline: Conversion of grasslands and pasturelands to agriculture and destruction of ground squirrel colonies have been the main factors causing the decline of the Burrowing Owl population (Zarn 1974b). Assimilation of poisons applied to ground squirrel colonies has probably
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also taken a toll. Their propensity for nesting in roadside banks also makes them particularly vulnerable to roadside shooting, being hit by cars, road maintenance operations, and general harassment. Vicenty (1974) reported three nests destroyed by road construction and one burrow deliberately destroyed by motorcyclists.
Recommendations: (1) Encourage farmers to protect this rodent_eating owl and to avoid disturbing nesting burrows and areas around nest sites. If farmers were made aware of the feeding habits of this bird, they might be more inclined to spare its nest sites from the plough. (2) Protect ground squirrel colonies supporting Burrowing Owls. (3) Manage upland areas in state and federal wild_ life refuges to benefit this species.
SPOTTED OWL (Strix occidentalis)
Status and range: This species is an uncommon permanent resident in heavily forested areas in the coastal ranges of southern California from San Luis Obispo Co. to San Diego Co., including the San Bernardino and San Jacinto mountains, along the coast of northern California from Marin Co. north, and in the Sierra Nevada from Plumas Co. to extreme northern Kern Co. (Grinnell and Miller 1944, Gould 1974). Isolated populations also occur in the Santa Cruz Mountains and Santa Lucia Mountains (Gould 1974). A total of 192 territories was located in a recent survey of the population in California; an average distance of 2.2 miles between adjacent pairs indicates a very low density in comparison to other birds (Gould 1974). Further surveys have now pinpointed a total of 317 territories (Gould 1977). This species' presence at only 73% of the historically occupied sites surveyed indicates a significant decrease in population levels. This estimate of a 27% reduction in occupied sites is conservative since a majority of these historical sites are on protected lands and did not include areas of major habitat disruption where absentee rates would certainly be much higher (Gould 1974). The extensive logging which has occurred in the Sierra Nevada and along the north coast certainly must have reduced populations of this species which favors virgin timber.
Reasons for the decline: Habitat destruction, primarily due to logging, is the major threat (Zarn 1974a). Fortunately, much suitable habitat remains in regional and state parks. Nest sites within parks are potentially threatened by increased human use and associated disturbances.
Recommendations: (1) Protect large tracts of old growth, multilayered forest in nesting areas using the guidelines proposed by Gould (1974). (2) Survey public and private lands proposed for timber sales to determine if Spotted Owls are present. (3) Where Spotted Owls are known to occur, selectively cut and thin forest instead of clear cutting, retain hardwood understory, and save nest trees. (4) Although this species seems tolerant of low levels of inadvertent human disturbance, known nest sites in parks should be protected from human disturbance and access should be restricted.
LONG_EARED OWL (Asio otus)
Status and range: Once a common to abundant permanent resident in many parts of California, this species had begun to decline by the 1940's (Grinnell and Miller 1944), and decline has continued through the present. Now any sighting of a Long_eared Owl is unusual, although this secretive species may be more common than the paucity of recent records indicates. Areas in which the decline has been most severe are the Sacramento Valley, where it is probably extirpated (Gaines 1974, pets. comm.), the San Joaquin Valley (R. Hansen, pers. comm.), and the San Diego
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area (P. Unitt and J. Dunn, pers. comm.). All three of these areas were once considered "centers of abundance" for this species in California (Grinnell,and Miller 1944). Sharp (IL907) found the owl to be very common in the Escondido area of San Diego Co.: "Common resident. Up to a few years ago almost every old crow's, hawk's, or rat's nest along the river in San Pasqual had its pair of owls." This species has not been recorded in this area in many years. It was formerly a fairly common resident in the Los Angeles region (Willett 1912) where today it is seldom reported. No nests have been reported in recent years in the San Francisco Bay area., where it was once considered a sparse local breeder (Grinnell and Wythe 1927). This species was fairly common and breeding in Santa Cruz Co. at the turn of the century. Five nests were located as recently as 1947, but today it no longer breeds (R. Morgan, pers. comm.). It has also disappeared from the Santa Barbara area as a breeding species. The last nesting in this area was recorded in 1972 (P.
Lehman, pers. comm.). Populations in the Yosemite National Park area have also declined (Gaines 1977). Numbers elsewhere in California are very low but may have always been so. The Long_eared Owl is still fairly common in willow thickets along the Susan River and other streams in the Honey Lake area (T. Manolis, pers. comm.) and in the Owens Valley (T. Heindel, pers.comm.). Small numbers also breed at certain desert oases, such as Yaqui Wells, San Diego Co., Morongo Valley, San Bernardino Co., and Oasis Ranch, Mono Co. The status of this species in the montane regions of California is poorly known.
Reasons for the decline: Destruction of lowland riparian woodland has played a role in the decline, but the absence of this species from existing riparian areas and its disappearance from many areas before the habitat was destroyed indicates that other factors are involved. Sharp (1907) was perplexed by this species' decline in the Escondido area: "Of late, for some unknown reason, they have been less plentiful. As probably half of the eggs produced were successfully hatched (to make a very low estimate) and the birds are seldom molested, it is rather difficult to account for their apparently diminishing numbers." Road kills by high_speed cars may have an impact on populations, as the birds seem very prone to collide with autos (R. Stallcup, pers. comm.). This species' nests are rather conspicuous, making the birds vulnerable to shooting and harassment (D. Gaines, pers. comm.).
Recommendations: (1) Protect lowland riparian habitat, particularly along the Owens River in the Owens Valley and the Susan River in the Honey Lake area, and also in the Central Valley and coastal San Diego Co. (2) Conduct surveys to determine whether population status warrants placement of Long_eared Owl on Highest Priority List.
SHORT_EARED OWL (Asio flammeus)
Status and range: Small numbers once bred locally throughout California where suitable habitat was available (Grinnell and Miller 1944). Now this species has completely vanished as a breeding bird from the southern coastal area (J. Dunn, P. Unitt, pers. comms.) and perhaps the San Joaquin Valley (R. Hansen, pers. comm.). A nest near Davis in 1976 was the first nesting record in many years in the Sacramento Valley (Winter and Erickson 1976, Chandik and Baldridge 1967). The only currently known nesting localities near the coast are Bair Island in San Francisco Bay (Remsen and Gaines 1973a, Gill 1977), the mouth of the Salinas River, Monterey Go. (Greenberg and Stallcup 1974; B. G. Elliott, pers. comm.; Winter and Morlan 1977), and perhaps near Moss Landing (Remsen and Gaines 1973a). Although it nested at the Palo Alto Baylands for at least two years (Greenberg and Stallcup 1974), it has not done so in the last three years (T. Chandik, pers. comm.). This species formally nested in the Mono Lake area but is no longer known to do so
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(Gaines 1977). A few pairs are presumably nesting at Honey Lake Wildlife Area (T. Manolis, pers. comm.). Status elsewhere in northeastern California is poorly known.
This species is more common in winter, but certainly can no longer be considered "common" as it was by Willett (1912) and Grinnell and Miller (1944), who noted a reduction it wintering populations even by the 1940's. it is now decidedly uncommon in winter in southern California (McCaskie 1974c). The Short_eared Owl has declined in many parts of North America.
Reasons for the decline: Destruction of marsh and tall grassland habitat in lowlands is certainly the main cause for the decline. Grazing of existing marshes and tall grasslands and shooting have apparently eliminated most birds in remaining habitat. This species is especially vulnerable to shooting.
Recommendations: (1) Protect existing marshes and ungrazed grasslands in the lowlands. (2) Edocate the public on the value of raptors and the fines for shooting them.
GILA WOODPECKER (Centurus uropygialis)
Status and range: This species is a permanent resident in riparian woodland and cottonwood groves along the Colorado River (Grinnell and Miller 1944), but numbers have greatly declined in the last few decades (G. McCaskie, pers. comm.), it is now found at only a few scattered localities. This is a dramatic change from the situation described by Grinnell (1914): "Common and characteristic resident the whole length of the region from Needles to the vicinity of Yuma. Found at every station on both sides of the river. While regularly present in the willows and cottonwoods of the river bottom, the species occurred also up the desert washes a mile or more from the edge of the riparian strip" Hollister (1908) described it as common in timbered bottomlands of the Colorado River near Needles, which is no longer the case.
The Gila Woodpecker expanded its range into the Imperial Valley in the early 1900's (Grinnell and Miller 1944) and up until recently, was found wherever there were cottonwoods; virtually every farmhouse had a pair (G. McCaskie, pers. comm.). Now this population has been reduced to a few pairs near Brawley.
Reasons for the decline: Destruction of the riparian woodland of the Colorado River Valley is the main reason for the decline. Displacement from nest sites by Starlings may also have affected this species. The Imperial Valley, where habitat still exists, lacks Gila Woodpeckers but now has many Starlings (G. McCaskie, pers. comm.).
Recommendations: (1) Protect riparian woodland in the Colorado River Valley and cottonwood groves in the Imperial Valley. (2) Acquire land suitable for restoration of riparian woodland in the Colorado River Valley (see Gilded Flicker). (3) Experiment with Starling control methods near Gila Woodpecker nesting sites.
BANK SWALLOW (Riparia riparia)
Status and range: This species once bred locally throughout much of California in the lowlands (Grinnell and Miller 1944). It once bred along the coast from Santa Barbara Co. to San Diego Co. but it has since completely disappeared as a breeding bird from southern California (J. Dunn, pers.
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comm.). Numbers elsewhere in the state have also been reduced. For instance, the Bank Swallow was described as common to abundant around Santa Cruz Co., and there were still some colonies active into the early 1960's. Now it is extirpated from Santa Cruz Co., where at least six former colonies are inactive (R. Morgan, pers. comm.).
Elsewhere, the only known breeding areas are: Ocean Beach, San Francisco Co. (100 pairs; Cutler and Pugh 1960); Ano Nuevo Point, San Mateo Co. (six pairs; Stallcup and Greenberg 1974b); along Trafton Rd. on the Pajaro River, Monterey Go. (under 50 pairs; Greenberg and Stallcup 1974); just north of King City, Monterey Co. (15_20 pairs; R. Branson, pers. comm.); between Red Bluff and Tehama on the Sacramento River (five colonies with a total of 442 birds;
Stallcup and Winter 1976a); near Chico, Butte Co. (23 pairs; Greenberg and Stallcup 1974); several localities in the Sacramento area (ABF); the Honey Lake area (one or two colonies; T. Manolis, pers. comm.); vicinity of Lower Klamath National Wildlife Refuge (several colonies; M. Taylor, pers. comm.). This species apparently no longer breeds in the Owens Valley (T. Heindel,
pers. comm.). The total population breeding within the State is extremely low relative to that of other species of swallows.
Reasons for the decline: Unknown, especially for coastal populations where coastal cliffs used for breeding are often still intact. Inland, channelization of rivers and erosion_control and bank stabilization programs have destroyed former nesting sites. Channelization of rivers is the most insidious, long_term threat to this species; almost all colonies in the Sacramento Valley will be destroyed by planned bank "protection" projects by the Army Corps of Engineers. Breeding in compact colonies makes this species vulnerable to harassment by humans, and the low number of colonies in California augments this vulnerability. The Pajaro River colony is currently threatened by hill_climbing motorcyclists.
Recommendation: Protect all remaining nesting colonies in California from habitat destruction and from human harassment.
PURPLE MARTIN (Progne subis)
Status and range: At one time, the Purple Martin was a fairly common breeder in the coast ranges the length of the state and in smaller numbers in the Sierra Nevada. It was even thought to be increasing in some populated areas (Grinnell and Miller 1944). In the last 15 years, there has been a dramatic decrease in southern California where it was once a common breeder in the mountains and where it even nested in some lowland residential areas (Willett 1912). The decline has been so drastic that fewer than a dozen birds were reported in summer 1976 (McCaskie and Pugh 1964; McCaskie 1973b, 1974b, 1975a, 1976b; A. Fries, pers. comm.; G. S. Suffel, pers. comm.). In the 1920's, this species even nested in downtown Pasadena and Newport Beach (Rowland Ross, pers. comm. to G. S. Suffel), but the situation now is so severe that in 200 hours of field work in the San Bernardino Mountains in 1977, not a single bird was seen (K. Garrett, pers. comm.). Decreases have been noted in Tehama County in the riparian habitat along the Sacramento River (T. Stone, pers. comm.). Decreases have been noted in Marin Co. (DeSante and Remsen 1972; W. M. Pursell, pers. comm.), Santa Cruz Co. (R. Morgan, pers. comm.), the Diablo Range (A. Edwards, pers. comm.), and the Oroville area (S. Laymon, pers. comm.). Numbers in the Sacramento area and along the north coast are apparently holding their own. Numbers in the Sierra foothills are low but have probably always been so.
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Reasons for the decline: Introduced Starlings have been noted ousting Purple Martins from nest cavities at a number of localities, and competition for nesting sites with Starlings is likely to be at least partly responsible for the decline. Removal of dead trees (snags) has eliminated nesting sites in several areas.
Recommendations: (1) Experiment with methods for Starling control at Purple Martin nest sites. (2) Retain snags wherever possible, these are important nest sites for this species as well as bluebirds, chickadees, nuthatches, etc. (3) Erect nest boxes in areas where Purple Martins still nest. Artificial nest boxes have been used by martins in Oregon (K. Klimkiewiez fide A. Craig).
BLACK_TAILED GNATCATCHER (Polioptila melanura)
Status and range: Two distinct subspecies are permanent residents in California: P. m. lucida in the southeastern deserts north to southern Inyo Co. and northwestern San Bernardino Co., and P. m. californica in coastal southern California north to Ventura Co. (Grinnell an7d Miller 1944). Populations of californica are now very reduced and extremely local. Numbers have declined throughout much of its range (McCaskie and Pugh 1964), a decline noticeable by the 1940's (Grinnell and Miller 1944). This subspecies was once a common resident in the southern coastal area (Willett 1912). There are no recent records from Ventura Co. and populations in Los Angeles Co. are very small and local, with a center of abundance on the Palos Verdes Peninsula (J. Dunn and H. L. Jones, pers. comm.). Of 13 Christmas Counts within this subspecies' range in the southern coastal area, in 1976 only three recorded Black_tailed Gnatcatchers (seven at San Diego, six at Palos Verdes, and three at Oceanside_Vista_Carlsbad); this is an amazingly low total considering the huge number of party_hours involved on these counts.
Populations of lucida have declined in the Imperial Valley and Coachella Valley; once fairly common In these areas, this species is now very difficult to find. For example, the 1976 Christmas Counts at the Salton Sea recorded three birds at the north end and one at the south end; this compares with 87 Verdins at the north end and 254 at the south end; the Verdin has similar habitat requirements and is more or less th