Item 7.1 Att 4 (5) Ex A - Final_EACCS_Oct2010_Print - City of Dublin

Chapter 2 Environmental Setting
wildlife linkages. Some species require linkages for periodic migrations among
different habitat types used for breeding, birthing, feeding, or roosting. Wildlife
movement from one important habitat area to another may vary from daily to
seasonal migration depending on the species. The second need for a linkage is
the permanent immigration or emigration of individuals among habitat patches,
allowing for gene flow and recolonization after local extinction (Beier and Noss
2000; Hilty et al. 2006; Groom et al. 2006).
Linkage requirements differ greatly from species to species. Specific
characteristics of linkages, such as dimensions, location, and quality of habitat,
can influence wildlife use. Wider linkages are more effective than narrower
linkages (Merenlender and Crawford 1998, Hilty and Merelender 2004; Hilty et
al. 2006; Groom et al. 2006). In addition, linkages that do not include adequate
buffers from the urban interface or disturbed areas are not used as often. A
linkage that does not function properly can become a “death trap” either by
isolating individuals from a core population or by not delivering them to habitat
that meets basic requirements for survival and reproduction (Groom et al.
2006).
All of the focal species, to some degree, rely on habitat linkages to maintain
populations and their genetic integrity. However, some of the more mobile
focal species rely on habitat linkages extensively for movement. For example,
San Joaquin kit fox moves through the Altamont Hills between populations in
the southern portion of its range and Contra Costa County. Golden eagle also
moves extensively through the study area during migration and for local
foraging while resident in the area. The Pacific Flyway, which diverges into east
Alameda County, is an important migration movement corridor for raptors and
other bird species. Bobcat and cougar also commonly traverse this area in
search of food. These species are examples of relatively long-distance
movement that requires consideration of habitat linkages at a larger scale. In
contrast, California tiger salamander and California red-legged frog move over
smaller distances, often from pond to pond or wetland to stream. Their
movement needs must therefore be considered at a more local scale, within the
study area.
Based on an assessment of the movement needs of the focal species and in
order to assess and ultimately conserve connections at the scales discussed
above, three categories of linkages are discussed below:
• grassland corridors in east Alameda County,
• aquatic-upland connectivity throughout the study area, and
• riparian/stream connectivity throughout study area.
East Alameda County Conservation Strategy 2-77 October 2010
ICF 00906.08