Vulnerability of birds to climate change in California's Sierra Nevada

In a rapidly changing climate, effective bird conservation requires not only reliable information about the current vulnerability of species of conservation concern, but also credible projections of their future vulnerability. Such projections may enable managers to preempt or reduce emerging climate-related threats through appropriate habitat management. We used NatureServe’s Climate Change Vulnerability Index (CCVI) to predict vulnerability to climate change of 168 bird species that breed in the Sierra Nevada mountains of California, USA. The CCVI assesses species-specific exposure and sensitivity to climate change within a defined geographic area, through the integration of (a) species’ range maps, (b) information about species’ natural history traits and ecological relationships, (c) historic and current climate data, and (d) spatially explicit climate change projections. We conducted the assessment under two different downscaled climate models with divergent projections about future precipitation through the middle of the 21st century. Assessments differed relatively little under the two climate models. Of five CCVI vulnerability ranking categories, only one species, White-tailed Ptarmigan (Lagopus leucura), received the most vulnerable rank, Extremely Vulnerable. No species received the second-highest vulnerability ranking, Highly Vulnerable. Sixteen species scored as Moderately Vulnerable using one or both climate models: Common Merganser (Mergus merganser), Osprey (Pandion haliaetus), Bald Eagle (Haliaeetus leucocephalus), Northern Goshawk (Accipiter gentilis), Peregrine Falcon (Falco peregrinus), Prairie Falcon (Falco mexicanus), Spotted Sandpiper (Actitis macularius), Great Gray Owl (Strix nebulosa), Black Swift (Cypseloides niger), Clark’s Nutcracker (Nucifraga columbiana), American Dipper (Cinclus mexicanus), Swainson’s Thrush (Catharus ustulatus), American Pipit (Anthus rubescens), Gray-crowned Rosy-Finch (Leucosticte tephrocotis), Pine Grosbeak (Pinicola enucleator), and Evening Grosbeak (Coccothraustes vespertinus). Species associated with alpine/subalpine habitats and aquatic habitats received significantly more vulnerable rankings than birds associated with other habitats. In contrast, species of foothill, sagebrush, and chaparral habitats ranked as less vulnerable than other species, and our results suggest these species may respond to climate change in the region with population increases or range expansions.