SAN FRANCISCO WATCH LIST- compiled by Dan Murphy
Francisco lost another species in the year 2000. Wrentit joined a very long list of species extirpated from the City. The event passed without fanfare or news coverage. Perhaps a dozen people are even aware of the passing of Wrentit from the city's avifauna. It is in the memory of the Wrentit that the Golden Gate Audubon Society prepared this list of San Francisco's own recently extirpated and endangered species.
The City of San Francisco boasts a bird list of 365 species. That is an incredibly large number of birds for a peninsula with an area of approximately 49 square miles. Most of the species on our watch list are not threatened with extinction. They are doing as well as any organisms faced with the overwhelming tide of urbanization and the environmental impacts that accompany it. What has happened and continues to happen in San Francisco can be expected to happen elsewhere as urbanization changes our natural world. Unless we change the way we interact with the environment, the slow death of our natural world will spread until it finally comes to the public eye that little remains of what was once a natural abundance. Strategies must be developed now to enable wildlife to coexist within the almost perpetual wave of urbanization that is covering California.
There are factors we have not mentioned specifically, but which most certainly carry the potential for reducing our bird population. Migrating birds no doubt fly into lighted towers as they do elsewhere in the U.S. where tower kills are well documented. Pesticides, herbicides and other poisons have probably taken a toll. The failure to protect our backyard habitat from concrete, brick and rock factors into the equation.
The recent spread of the Red Fox across San Franicsco is of particular concern for ground and marsh nesting birds.
The city of San Francisco was urbanized between the California gold rush which began in 1848 and the early 1950's. During that period the footprint of the city covered what had been natural habitat. In just over 100 years most of the natural habitat was lost and the new urban habitat was developed. During the second half of the 20th Century, San Francisco's footprint did not change substantially. One might think the changes brought about by such a dramatic change would stop when the last sections of the Sunset District were built after World War II. That has not been the case.
The following is a list of 33 birds. Seven species no longer inhabit San Francisco during part or all of the year. Those birds are now extirpated, or locally extinct. Six additional species are under such pressure that it is very likely they will join the list of extirpated species in the foreseeable future. An additional 20 species are so vulnerable to extirpation that if a catastrophe impacts their limited habitat in San Francisco they will loose their tenuous foothold.
These are species of birds that no longer regularly occur in San Francisco during all or part of the year. They have been lost during recent years. Many other species were extirpated during the initial stages of urbanization in San Francisco. The birds mentioned here were lost during the post urbanization period. This is a period we view as being changed from the natural environment of San Francisco, but one in which the environment is fairly stable in its own right.
Status in SF: The population of American Bittern in San Francisco was never high. This species was extirpated from Lake Merced during the late 1970's during a period of drought when the lake's level dropped and the marshes in which it resided were stranded above water level. There were single sightings in 1996 and 1998. Reports from outside San Francisco indicate the species is not as common as it once was. There are no SF nesting records.
Conservation: Preservation of expanses of bulrush is critical for this species if it ever returns to SF. Lake Merced is the only site in San Francisco which provides habitat suitable for American Bittern.
Status in SF: Formerly wintered in Golden Gate Park in numbers of up to 50 per winter. The population dropped during the mid 1970s. There are single records each year in Golden Gate Park and at the SF Zoo, but most are spring and fall migrants. There are no SF nesting records.
Conservation: It is probable the loss of this species is related to the loss of nesting habitat outside the City. It appears habitat in city parks is relatively unchanged since these ducks were regular winter residents. The placement of nest boxes in lakes in Golden Gate Park and at the San Francisco Zoo might have the potential of extending the breeding range of this species to San Francisco County.
Status in SF: Formerly occurred in open areas such as Lake Merced, Golden Gate Park, McLaren Park and Candlestick Park. There are no nesting records for SF County. It is now accidental, occurring some years but not all. During the past year they were reported from Candlestick Park and Golden Gate Park Buffalo Paddock.
Conservation: Restoration of this species is unlikely. It's habitat requirements seem inconsistent with dense urbanization, even with parklands which are available in SF. The mesa at Lake Merced once supported a wintering shrike. It's occurrence stopped when trees were planted to screen the open area from the Lake Merced Blvd. The marginal numbers of birds at Candlestick Point were lost when the State Park was developed.
Status in SF: This species occurred in small numbers in dirt parking lots at Candlestick Park. It was never a breeding species in SF. 10+/- birds were resident in the dirt parking lots near Candlestick Park. The population declined when Candlestick State Park was developed. It was always marginal at best, but appears extirpated now.
Conservation: The loss of this species will probably not be mitigated. Its habitat needs for large expanses of open ground would appear not to be available in SF.
Status in SF: This formerly common breeding species in our forested parks is now extirpated during the nesting season. Since it is an irruptive migrant, fall records varying from a few birds to hundreds which remain into winter.
Conservation: Habitat loss due to forest maturation and competition with European Starling, Pygmy Nuthatch and other cavity nesters are the most likely causes for the loss of this species. One of the last 2 known nests (early 1980's) was lost when the Monterey cypress in which it was nesting was cut by Rec and Park crews. A second nest was lost when the pinaster pine in which it was located blew down during an unseasonal storm.
Status in SF: extirpated in 2000. This is a non migratory, limited range, species that inhabits coastal scrub and other shrub lands.
The Presidio of San Francisco and Lake Merced where the last places Wrentits seemed to remain in SF. The Baker's Beach population has been noted for several years, but it has not been reported in the 2000 season. The Lobos Creek population was found during the past 5 years but has not been noted for at least 2 seasons. The Lake Merced population was most likely a single bird that was heard singing at the northeastern area of the lake in 1997, 1998 and 1999.
McLaren Park: A single bird was observed in a cypress tree in the spring of 2000. The bird was not found after the initial sighting.
Conservation: This species' decline is most likely due to loss of habitat in terms of total area and fragmentation. As the coastal scrub and willow habitats in which it can be expected to reside were destroyed for urban development and naturalistic parklands the remaining population of this species was isolated and apparently reached the threshold beyond which it could not sustain itself.
Status in SF: Singing males have been noted at Lake Merced through the nesting season in the past. There is no recent evidence of breeding. It is uncertain whether local conditions or a range wide population decline are the reason for the probable loss of this breeding species. None have been reported in recent years. This is a common migrant in fall and it is uncommon in spring. It is a rare winter resident that has been recorded regularly at Lake Merced.
Conservation: Preservation and restoration of riparian habitat may enable this species to return at some point.
HIGH EXTIRPATION POTENTIAL
The following species have very low populations and appear to be loosing numbers. It is likely they will join the extirpated list if radical action is not taken to protect them and their surroundings and to increase their habitats.
Status in SF: A wintering flock of 15+/- can be found on Ocean Beach between Sloat Blvd. and Lincoln Way during the period of July through April. There are no breeding records for SF County. Single birds have been noted at the beach at Crissy Field, though not in the past few years. It is likely they use beaches or uplands away from Ocean Beach during winter storm tides.
Conservation: The single flock of Snowy Plovers is subject to impacts from off leash dogs, people walking and running on the beaches, natural predators such as gulls, hawks, etc., and most recently from National Park Service vehicles which patrol Ocean Beach.
Status in SF: Nearing extirpation. The Presidio of San Francisco appears to hold the last viable California Quail population. The few birds in Golden Gate Park are restricted to the Arboretum. The Fort Funston population has been noted during the spring for the past 2 or 3 years. The species has not been noted in 2000. It is likely there is a remnant population in the Olympic Club Golf Course. A few birds were released near the Rod and Gun Club at Lake Merced during the fall of 1999, but they have not been reported since early spring 2000.
Conservation: Cat and dog predation appear the most likely cause of the population decline. Quail consistently disappeared from parks as cat colonies were established. They also disappeared from parklands as unleashed dog walking became a common practice in parks such as Fort Funston and Sigmund Stern Grove. Predation by Scrub Jay has been observed in the Arboretum. Predation by other corvids is likely. The recent appearance of red foxes in San Francisco poses another serious threat to our remaining quail. Habitat seems relatively unchanged since there were hundreds of birds. It is likely restoration of native scrub habitat would benefit the species.
Status in SF: Nesting remains probable in Golden Gate Park, Land's End, the Presidio, Mt. Davidson, McLaren Park and Glen Park. Fewer than 10 probable nesting pairs are reported each year.
Conservation: Habitat is limited because of limited use of oaks in SF parks. Air pollution is a limiting factor in lichen growth, necessary for nest building. This seems less a problem than in the past. This species is subject to Brown-headed Cowbird parasitism.
Status in SF: It is listed as threatened by the State of California because of habitat loss in the Central Valley. Once widespread on the coast it is now limited to 2 confirmed colonies. Habitat for this colonial species is sand bluffs in close proximity to fresh water marsh lands. This species breeds at a single site in the exposed bluffs of the Merced Formation at Fort Funston facing the ocean. Their sole feeding site is at Lake Merced and its vicinity.
Conservation: Limited habitat make the Bank Swallow subject to any of a number of environmental impacts including but not limited to unseasonal storms, landslides at the colony site, vandalism of the colony, predation by ravens and other predatory birds, destruction of the food source at Lake Merced, and pesticide use at nearby golf courses. Protection of the nesting cliffs at Fort Funston is critical for the continued existence of Bank Swallows in San Francisco.
Status in SF: Birds have been extirpated from all of the City except for the west side of Lake Merced and Fort Funston where it is known to breed. There are probably fewer than 10 pairs remaining. Status in winter may be higher due to migratory birds.
Conservation: Habitat loss is the most likely reason for the loss of this species. It is abundant elsewhere, but lack of habitat in SF is an identifiable problem. Removal of exotic trees and shrubs at Fort Funston would most likely cause the extirpation of Bewick's Wren from San Francisco.
Status in SF: The population is rapidly declining and extirpation is imminent. This species remains wide spread but in continually declining numbers. They were noted during the spring of 2000, on Mt. Davidson, above Baker's Beach in the Presidio, and it is likely other birds remain in the oak woodlands in the eastern part of Golden Gate, McLaren and Glen Parks.
Conservation: Habitat loss appears to be a major factor in the loss of this species. The removal of dense ground vegetation in De la Veaga Dell in Golden Gate Park ended this species' use of that area. It is likely that is the cause of its disappearance elsewhere in SF. Its decline parallels the increase of off-leash dog walking and feral cat feeding. It is likely uncontrolled pets have a significant impact on this species.
VULNERABLE TO EXTIRPATION
The following species are not imminently threatened with extirpation, but their numbers are few and/or their habitat is limited, so a single event could eliminate them from the San Francisco avifauna.
Status in SF: This species is resident throughout the year. It has only nested at Lake Merced since about 1995. There is a large colony on the underside of the San Francisco Oakland Bay Bridge which straddles the county line. They can be found in all lakes, the bay and the ocean.
Conservation: This species is threatened by reconstruction of the San Francisco Bay Bridge. The Lake Merced population is threatened by fishermen who are frequently seen throwing rocks or shooting at them with slingshots from fishing beaches. The possibility of impacts from tree trimming, or actual tree removal, in the eucalyptus groves adjacent to Skyline Blvd. must be considered a serious threat to Double-crested Cormorant.
Status in SF: This species nests on Seal Rocks and perhaps on Alcatraz. It is also breeds on the Farrallon Islands and elsewhere along the coast. It is present throughout the year. Brandt's Cormorant is highly variable in numbers. Nesting appears related to food sources so its status from year to year is in question.
Conservation: Brandt's Cormorant is subject to the same impacts as other coastal nesting species. Oil spills are pr imary among these. Impacts from commercial fishing and jet skis have been observed.
Status in SF: A few pairs may breed on the cliffs just north of Sutro Baths. Small numbers can be found in SF coastal water throughout the year.
Conservation: Subject to impacts from oil spills and perhaps people climbing on the cliffs near nesting or roosting sites.
Great Blue Heron
Status in SF: Individuals are regular in SF during the non breeding season. Non breeding birds remain in the City during the nesting season. During the past several years a colony has been established at Stow Lake in Golden Gate Park and 2 colonies have been established at Lake Merced. In all there are presently about a dozen nests in SF.
Conservation: Great Blue Heron appears to be doing well in the Bay Area. The problem for the SF population is the impact of urbanization. The birds at Stow Lake are subject to impacts from park crews who may trim trees too close to the nesting trees or who may cut trees with nests. There are potentially the same impacts for the Lake Merced colonies. The Golden Gate Park population is also subject to nest loss from over aged trees which may blow down in a storm. This is less likely for the Lake Merced population which nests in eucalyptus which are not as old as the Golden Gate Park trees. Both populations are subject to impacts on food availability such as might occur with lake restoration projects.
Status in SF: All known breeding records are from Lake Merced. Migrants are recorded annually in Golden Gate Park and Pine Lake.
Conservation: This species appears stable in SF. Any projects that increase or decrease water levels at Lake Merced, cuts willow stands, or removes large amounts of bulrush should consider impacts on this species.
Formerly listed as endangered by the Federal Government.
Status in SF: Peregrine Falcon nests on the underside of the Bay Bridge. One pair apparently feeds in downtown San Francisco and hunts from tall buildings. Over-wintering birds feed along the bay and ocean coast of SF.
Conservation: Nesting birds could be impacted by construction on the San Francisco Oakland Bay Bridge. Any loss of coastal wetlands could have an indirect impact on this species.
Status in SF: Present through much of the year at Lake Merced and infrequently in wetlands elsewhere. Virginia Rail is not known to breed in SF. Any major project which would destroy the marsh would seriously impact this species and perhaps drive it to extirpation. A sewage spill in Lake Merced would also have the potential for catastrophic impacts on this species.
Conservation: This species appears stable in SF. Any projects to increase or decrease water levels at Lake Merced, or to remove large amounts of bulrush should consider impacts on this species.
Status in SF: Present through much of the year at Lake Merced and infrequently in wetlands elsewhere. Sora is not known to breed in SF. Any major project which would destroy the marsh would seriously impact this species and perhaps drive it to extirpation. A sewage spill in Lake Merced would also have the potential for catastrophic impacts on this species.
Conservation: This species appears stable in SF. Any projects to increase or decrease water levels at Lake Merced, or to remove large amounts of bulrush should consider impacts on this species.
Status in SF: A few pairs annually breed on the cliffs just north of Sutro Baths.
Conservation: Subject to impacts from oil spills and perhaps people climbing on the cliffs.
Status in SF: The population is limited to a single pair that breeds on Seal Rocks and perhaps a one or two others on the cliffs at Land's End. The species is present throughout the year.
Conservation: Subject to impacts from oil spills and predation from Western Gulls.
Status in SF: This species is regular, though low in numbers along the bay shore of SF. The breeding population is limited to a couple of pairs which may breed at Pier 98/Heron's Head Park. Individuals are noted annually at other sites along the Bay and at Lake Merced.
Conservation: Major threats would be from off leash dogs or from people walking on nests. Gull or Raven predation may also be a problem.
Status in SF: This species has been noted most recently at Lake Merced. Reports of Barn Owls in the trees near the maintenance buildings at Harding Golf Course are made annually. There have been recent reports from around Hunter's Point. The Golden Gate Park population seems to be extirpated. They roosted in the trees across the street from Mallard Lake, but since the trees were trimmed several years ago there have been no reports and their pellets are no longer found in the area.
Conservation: The SF population is limited and poorly understood. It is certain Barn Owl is marginal as an SF species.
Western Screech Owl
This is a nocturnal owl that resides in oaks and associated woodlands.
Status in SF: Populations have been recorded in the eastern end of Golden Gate Park and near the Arguello Gate of the Presidio.
Conservation: The very low numbers of this species and the limited knowledge we have of them make their situation difficult to assess. They may have been displaced from de la Viega Dell when the Aids Memorial Grove renovation took place. Care of oak woodlands and their understory are critical to the continued existence of this species in San Francisco.
Status in SF: Olive-sided Flycatcher nests in parklands with mature stands of trees such as Golden Gate Park, the Presidio of San Francisco and on golf courses around Lake Merced. The population is highly variable apparently because of impacts on the wintering grounds in northern South America.
Conservation: Tree cutting in sensitive areas should be restricted to the period of August through February. Removal of mature trees where this species is known to nest should be minimal.
Nests in colonies on the sides of buildings. They feed over lakes, wetlands and parklands.
Status in SF: Nests in colonies on the concrete bridge at the south end of Lake Merced and on stable buildings in Golden Gate Park. It is probable other nest sites occur in SF. The Lake Merced colony is experiencing a drop in numbers from 48 in 1997, to 39 in 1998 and 1999, and down to 8 in 2000. The number of lost nests suggests the number of nesting attempts approached that of previous years, but many nests were broken. It is unknown whether this was done by predators or vandals.
Conservation: This species is threatened with loss through nest destruction by people. San Francisco State University cleared the library building of a colony a number of years ago. There is no suggestion or indication they did so during the nesting season. Swallow colonies are messy and bothersome to some, so there is pressure to remove them. They are also subject to vandalism. Existing colonies should be identified and protected. As new ones are developed they should be protected as well.
Status in SF: Inhabits marshes all year. All breeding records are for Lake Merced so any major work which would destroy the marsh would seriously impact this species and perhaps drive it to extirpation.
Conservation: This species appears stable in SF. Any projects to increase or decrease water levels at Lake Merced, or to remove large amounts of bulrush should consider impacts on this species. A sewage spill from the pipe line which crosses the southern end of the lake or from the storage box beneath John Muir Dr. could seriously impact Marsh Wrens.
Status in SF: Inhabits marshes and nearby uplands all year. There is some post breeding movement, so in fall migrant birds are often seen in Golden Gate Park and other places where they are not known to nest. All nesting records are from Lake Merced so any major work which would destroy the marsh would seriously impact this species and perhaps drive it to extirpation. Common Yellowthroat is subject to Brown-headed Cowbird parasitism.
Conservation: This species appears stable in SF. It is listed as a species of special concern by the federal and state governments, the Lake Merced population appears stable. Any projects that increase or decrease water levels at Lake Merced, of remove large amounts of bulrush should consider impacts on this species. A sewage spill at Lake Merced could seriously impact this species.
Status in SF: Breeds at Pier 98/Heron's Head Park in very small numbers. Wintering birds of several subspecies are uncommon at grassy and wetland parklands.
Conservation: Weedy shoreline vegetation forms the habitat base for this species. Habitat restoration may enhance it's presence in SF. Restoration to other habitat types could threaten this species with extirpation as a breeding bird in SF.
Widespread in parks and yards. Nests in low shrubs.
Status in SF: Once ubiquitous in the city's parks. the population of this species has crashed in recent years, particularly in Golden Gate Park. Documented problems include the increase of feral cats in many city parks, parasitism by cowbirds and the loss of scrub habitat. The recent appearance of red foxes in San Francisco is likely to put more pressure on this species. The population is enhanced by an influx of large numbers of over wintering birds.
Conservation: Loss of habitat and the presence of feral cats appear to be the primary problems for this species. Brown-headed Cowbird parasitism may be significant as well. White-crowned Sparrows have done well in restoration areas such as the north end of Fort Funston and above Baker's Beach.
Status in SF: The population of this ground nesting species appears to be in decline during recent years, particularly in Golden Gate Park. Problems include the increase of feral cats in many city parks and the loss of ground cover such as fallen branches under which juncos nest. Newly arrived red foxes may well be a serious threat to this species. The population is enhanced by an influx of large numbers of over wintering birds.
Conservation: Loss of habitat and the presence of feral cats appear to be the primary problems faced by this species. Brown-headed Cowbird parasitism may be significant as well. It is likely the population at Lake Merced/Harding Golf Course will be impacted by redevelopment of the golf course.