Montane-breeding bird distribution and abundance across national parks of southwestern alaska

Abstract

Between 2004 and 2008, biologists conducted an inventory of breeding birds during May–June primarily in montane areas (.100 m above sea level) of Aniakchak National Monument and Preserve (Aniakchak NMP), Katmai National Park and Preserve (Katmai NPP), and Lake Clark National Park and Preserve (Lake Clark NPP) in southwestern Alaska. Observers conducted 1,021 point counts along 169 transects within 63 10-km 3 10-km plots that were randomly selected and stratified by ecological subsection. We created hierarchical N-mixture models to estimate detection probability and abundance for 15 species, including 12 passerines, 2 galliforms, and 1 shorebird. We first modeled detection probability relative to observer, date within season, and proportion of dense vegetation cover around the point, then modeled abundance as a function of land cover composition (proportion of seven coarse-scale land cover types) within 300 m of the survey point. Land cover relationships varied widely among species but most showed selection for low to tall shrubs (0.2–5 m tall) and an avoidance of alpine and dwarf shrub–herbaceous cover types. After adjusting for species not observed, we estimated a minimum of 107 6 9 species bred in the areas surveyed within the three parks combined. Species richness was negatively associated with elevation and associated land cover types. At comparable levels of survey effort (n ¼ 721 birds detected), species richness was greatest in Lake Clark NPP (75 6 12 species), lowest in Aniakchak NMP (45 6 6 species), and intermediate at Katmai NPP (59 6 10 species). Species richness was similar at equivalent survey effort (n ¼ 973 birds detected) within the Lime Hills, Alaska Range, and Alaska Peninsula ecoregions (68 6 8; 79 6 11; 67 6 11, respectively). Species composition was similar across all three parks and across the three major ecoregions (Alaska Range, Alaska Peninsula, Lime Hills) that encompass them. Our results provide baseline estimates of relative abundance and models of abundance and species richness relative to land cover that can be used to assess future changes in avian distribution. Additionally, these subarctic montane parks may serve as signals of landscape change and barometers for the assessment of population and distributional changes as a result of warming temperatures and changing precipitation patterns.