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Grand Teton National Park Report

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Throughout North America, bird declines may be attributable to loss of habitat on the breeding grounds. Human land uses, especially residential development pressures within western ecosystems, are greatly impacting riparian landscapes and biota, particularly breeding birds. While most studies have focused on eastern birds, it is unclear how western bird assemblages respond to development and its concomitant effects on habitat alteration and fragmentation. I sampled bird community parameters and habitat variables at three spatial scales (microhabitat, macrohabitat, and landscape) along a human development gradient along the Snake River riparian corridor in Jackson Hole, WY. Fifty-six cottonwood forest patches were surveyed during the 2001-02 breeding season. Principal component analysis, canonical correspondence analysis, and multiple linear regression statistical tests were used to determine the effects of housing densities on avian assemblages, guilds, and habitat features. Overall species richness and diversity declined with increasing human development. Neotropical migrant species were most negatively impacted and consistently declined in proportional representation on forested plots as human development densities increased. Short-distance migrants, food generalists, ground gleaners, and avian nest predators all increased with increasing human development. Brood parasites, on the other hand, did not increase with increasing fragmentation and their distribution may reflect the availability of nest host species. Of the environmental variables measured, landscape features were most affected and metrics consistent with habitat fragmentation were most correlated with human development. These results suggest that residential development within riparian habitats may be exerting a strong negative influence on western bird communities and at high densities may lead to a depauperate avian biota and reproductive sinks.