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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR CITY OF SAN LEANDRO BIOLOGICAL RESOURCES Burrowing owl, also recognized as a SSC species, have been reported from the North Field at the Oakland Airport, and the state and federally endangered California least tern (Sterna antillarum browni) and the federally threatened western snowy plover (Charadrius alexandrinus nivosus) have been observed west of Runway 11/29 at the Oakland International Airport. Burrowing owl typically occurs in low grasslands, and marginally suitable habitat for this species occurs around the perimeter of the golf course on the Project site, although no occurrences have been reported in the past. California least tern and western snowy plover reportedly nested along the margins of the western runway at Oakland Airport, but haven't done so for over a decade and suitable nesting habitat for these species is absent on the Project site. A winter roosting colony of monarch butterfly (Danaus plexippus) occurs in the grove of blue gum eucalyptus in the southeastern portion of the Project site. This species has no legal protective status under the Endangered Species Acts, but roosting colonies are recognized as important biological resources by the CDFW and are subject to CEQA review with a State-wide ranking by the CNDDB of S3 or vulnerable (vulnerable in the state due to a restricted range, relatively few populations). According to monitoring performed by The Xerces Society from 2005 to 2009, an estimated 5,000 monarch butterflies overwintered in the rows of blue gum eucalyptus on the Project site, but this is a considerable reduction from the tens of thousands of monarchs observed in the late 1990s. The following provides a summary of the characteristic habitat and natural history of monarch butterflies, which are applicable to the wintering colony on the Project site. Monarch butterflies are a migratory species that cannot survive the colder winter months in most parts of North America, and travel to their overwintering areas during the fall months. Monarchs that live west of the Rocky Mountains migrate to coastal areas of California, while those that live east of the Rockies travel to a few sites in the mountains of Central Mexico. In coastal California, overwinter sites range from northern Baja California to southern Mendocino County. In California, clustering behavior begins once migrating monarchs reach their overwintering sites in the fall. The duration of residence is generally used to differentiate the types of monarch wintering habitats, with sites that support clusters of wintering monarchs for a few days to a month are referred to as temporary habitats. Sites that host clusters of wintering monarchs for one to six months are referred to as overwintering habitats. In the fall months, typically in September and October, numerous, generally small temporary aggregations are formed, especially in areas where nectar plants are plentiful. Monarchs at many of these sites disperse to part -term or full-term overwintering sites as nectar sources, air temperature, and day length decrease. Some sites may serve as overwintering sites one year and temporary sites another year, or a mixture of the two. Occasionally, previously utilized overwintering sites and/or temporary sites are abandoned for one or more seasons as a natural phenomenon. Overwintering sites are characterized by groves of trees of mixed height and diameter. Often there is a small clearing within a stand of trees, or formed by a combination of the trees and surrounding topography, to provide shelter for the butterfly. These overwintering sites protect the butterfly from prevailing on -shore winds and freezing temperatures, and provide opportunities for sunning and other behaviors. The vegetation serves as a thermal "blanket" which moderates extreme weather conditions. At some locations, topographic features as well as nearby buildings or other man-made structures may provide some protection as well. PLACEWORKS 4.3-9