6.19 MCLAREN PARK (continued)

WILDLIFE

Birds

The diversity of vegetation in McLaren Park provides suitable foraging, nesting, and roosting habitat for a wide variety of species. The grassland and scrub habitats of McLaren Park provide foraging habitat for raptors, while the forests provide potential nesting habitat for these species. Habitat for smaller birds like sparrows, finches, and flycatchers is available in the scrub and mosaic habitats throughout the park. Small amounts of riparian habitat along the water courses within the Natural Areas may be factor limiting bird diversity. As with many Natural Areas, the eucalyptus forests are relatively monotypic with sparse vegetation in the understory and therefore relatively poor habitat for birds.

Sensitive Bird Species and Important Bird Habitat

Of the bird species designated as sensitive for the entire Natural Areas, 23 species have been documented at McLaren Park (Table 6.19-2). Of these, nine species nest within the Natural Area. The forest habitat of McLaren Park provides nesting habitat red-tailed hawk (Buteo jamaicensis), red-shouldered hawk (Buteo lineatus), and American kestrel (Falco sparverius). These species forage in the grasslands of McLaren Park. Other species that nest within McLaren Park include American goldfinch (Carduelis tristis), lesser goldfinch (Carduelis psaltria), barn swallow (Hirundo rustica), tree swallow (Tachycineta bicolor), hooded oriole (Icterus cucullatus), and pygmy nuthatch (Sitta pygmaea). A wrentit (Chamaea fasciata) was reported singing from an area near the twin water tanks between Mansell Street and the golf course (Figure 6.19-9) on July 1, 2001 (Freed 2001). Wrentits may be extinct as a breeding population within San Francisco (Murphy 2000; SFFO 2001). Other passerines are likely to use the park, but specific occurrence of sensitive species is unknown. The California Natural Diversity Data Base (CNDDB) does not report the occurrence of any special-status species of birds from McLaren Park (CNDDB 2005). The variety of habitats available within McLaren Park help maintain the diversity of bird life. 
Sixteen areas of important bird habitat have been delineated within this Natural Area (Figure 6.19-8 to 6.19-10). Most of these areas are grasslands that support species like the western meadowlark (Sturnella neglecta) and American and lesser goldfinch. These areas also provide foraging areas for raptors that nest within the forests. Four other areas are primarily riparian willow thickets that provide habitat for Wilson’s warbler (Wilsonia pusilla), orange-crowned warbler (Vermivora celata), and Hutton’s vireo (Vireo huttoni). Scrub and forest habitats near the golf course and the outdoor theater in the central portion of the Natural Area have been mapped as important habitat for California quail. This species is rapidly vanishing from SanFrancisco and McLaren Park represents one of the last remaining viable habitats for this species. These areas may also provide habitat used by wrentit, Bewick’s wren (Thryomanes bewickii), Swainson’s thrush (Catharus ustulatus), and spotted towhee (Pipilo maculatus).
Other areas of important bird habitat include the forests that support nesting red-tailed and red-shouldered hawks and American kestrel.

Mammals

Surveys of small mammals were conducted at McLaren Park in summer 2000 (Paquin and Reading 2000). An array of 48 live traps was placed in south-facing grassland habitats at dusk and serviced the following morning. This pattern was repeated for four consecutive nights (192 trap nights) on August 7 to 11, 2000. Trapping resulted in the capture of six harvest mice (Reithrodontomys megalotis) and one house mouse (Mus musculus). One broad-footed mole (Scapanus latimanus) was found outside the trapping area (road kill). A carcass of a California meadow vole (Microtus californicus) was found in the southeastern grasslands (EIP field visit, October 27, 2001). It was within 6 feet of a relatively new brush pile that had been created within the grassland. Larger mammals found in McLaren Park such as raccoons, skunks, and opossum are typical of urbanized parks in general. The skeleton of a raccoon was found south of Mansell Street (EIP field visit, October 27, 2001). The CNDDB does not report the occurrence of any special-status species of mammals from McLaren Park (CNDDB 2005).

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Reptiles/Amphibians

Eight surveys for reptiles and amphibians, totaling approximately 36 hours of field effort, were conducted at McLaren Park in spring 2000 (Paquin and Reading 2000). During these surveys, conducted by walking transects, one Pacific chorus frog (Pseudacris regilla), 116 juvenile and adult bullfrogs (Rana catesbeiana), and one red-eared slider (Trachemys scripta) were observed in Yosemite Marsh and McNab Lake. Numerous juvenile and adult bullfrogs and three red-eared slider turtles were also observed (EIP field visit, April 12, 1999). The grasslands at McLaren Park may be large enough to support common reptiles such as pacific ring-neck snake (Diadphis punctatus), pacific gopher snake (Pituophis melanoleucus), California alligator lizard (Elgaria multicarinata), and northwestern fence lizard (Sceloporus occidentalis). Observations of the bullfrogs are important because bullfrogs can have negative impacts on native frog populations. The CNDDB does not report the occurrence of any special-status reptiles or amphibians at McLaren Park (CNDDB 2005).

Invertebrates

Sensitive Invertebrate Species

At least four special-status species of butterflies potentially occur within the City of San Francisco: mission blue butterfly, San Bruno elfin butterfly (Incisalia mossii bayensis), San Francisco silverspot, and bay checkerspot butterfly (Euphydryas editha bayensis). San Bruno Mountain, just south of McLaren, supports populations of all these species. Larval host plants for the mission blue and bay checkerspot butterflies are relatively common at McLaren Park. Eggs and larvae of the mission blue butterfly were found on lupines in the southernmost grassland of McLaren Park (near Geneva Avenue) in 1988 (Arnold 1988). This is the slope that faces San Bruno Mountain and where colonization of McLaren Park is the most likely. The larval host plant for the silverspot, Johnny-jump-up (Viola pedunculata) can be found on the south-facing grasslands (Figure 6.19-9). The larval host plant for the San Bruno elfin is broadleaf stonecrop (Sedum spathulifolium) which does not occur in McLaren Park. None of the other sensitive butterfly species have been reported from McLaren Park. A population of San Francisco fork-tailed damselfly was discovered at a small wetland and pond, known as Yosemite Marsh, in the northern portion of McLaren Park in 1998 (Hafernik 1999). Yosemite Marsh is located in a picnic area at the intersections of Bacon and Oxford streets (Figure 6.19-8). This marsh has been dredged recently to remove excess sediment and improve habitat for the damselfly. Small isolated populations of this species become extinct most often because of rapid changes in habitat conditions typically associated with the growth of emergent aquatic vegetation and the loss of open water areas.

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