Avian Inventory Of Yosemite National Park (1998-2000)

Siegel, Rodney; Desante, David

This document constitutes the draft final report of The Institute for Bird Populations' three-year Avian Inventory of Yosemite National Park. The inventory was designed to provide park managers with comprehensive, scientifically credible information about the distribution and relative abundance of the avifauna occurring within park boundaries. Specifically, we sought to achieve the following goals: a) document the occurrence of at least 90% of the bird species currently believed to occur in Yosemite National Park; b) estimate the species richness of each of about 30 bird-habitat types that are based on the major terrestrial plant communities within the park; c) describe the distribution and relative abundance of at least 90% of the bird species currently believed to occur in the park as a function of the various bird-habitat types, and d) provide summary information necessary to develop a general monitoring strategy and design that can be implemented in the park. We used timed point counts, coupled with detailed habitat descriptions of each point count location, as our primary means of surveying birds. We used the generalized survey protocol to conduct point counts at 2,646 locations across the length and breadth of the park. We recorded a total of 21,072 individual bird detections, 10,220 of which were within a 50m radius of the observer. Additional surveys using slightly different methodologies were conducted at 197 point count stations in developed locations throughout the park (campgrounds, picnic areas, stables, etc.) and at 46 montane meadows at varying elevations across the park (detailed results from montane meadow surveys are not in the body of this report, but are presented in Appendix One). We documented 149 species (105% of the 142 locally extant species on our predicted species list) in the park during the 1998-2000 field seasons, including 15 species not included on our predicted species list. Ninety-nine species were detected within a 50m radius during at least one point count. We present the relative abundance (average number of detections per hectare surveyed) of each of these 99 species in tabular form. We then use these detection rates and GIS-based park habitat data to produce predicted distribution and relative abundance maps of each of the 82 species detected five times or more during point counts. For species detected fewer than five times, we provide maps indicating the precise location of each detection. For the two habitats represented by the most points in our surveys of developed areas (Red Fir and Ponderosa Pine Mixed Conifer) we compare species detection rates in developed areas versus areas sampled by our generalized protocol. We report that serveral species are significantly over-represented in developed areats (most notably Brown-headed Cowbird which is a nest parasite, and Stellar's Jay, which is a nest predator), while numerous others are significantly under-represented in developed areas. For frequently detected species in well-surveyed habitats, we also use multiple logistic regression to describe the relationship between the likelihood of detection within the 50 m point count circle and each of a suite of ten predictor variables describing habitat characteristics of that circle. We provide logistic regression models describing habitat relationships for 21 species in one or more habitats. We conclude by suggesting four guidelines for prioritizing future avian monitoring efforts in the park, and outlining five specific projects that would fulfill those priorities.