Variation in Raptor Abundance Between Urban and Rural Habitats

Tolbert, Haley
Raptors are iconic apex predators of prairies and grasslands in Wyoming. Due to extensive habitat modification by urbanization, these landscape changes may lead to both threats and advantages, such as human-derived food sources, for raptors. This study explores (1) whether raptor density differs in urban and rural habitats, and (2) if the difference is due to increased food abundance in human-modified habitats. In summer of 2016, distance sampling and roadkill surveys, a proxy for prey density, were used to examine these questions. Raptors in prairie, grassland, and riparian habitats around Casper, WY were studied. Results indicate a lower abundance of raptors in human-dominated environments, with 1.9 per km2 in rural habitats versus 0.7 per km2 in urban areas. An AIC comparison of separate urban and rural models versus a combined model strongly supported modeling the two habitats separately. Significant differences between roadkill in different habitats existed, with a rural of average 1 per km and 0.4 per km in urban zones, suggesting rural prey density may be higher. While raptors and roadkill were positively correlated, this correlation was suggested abundance of both is greater in rural areas. This indicates that even in a state with a small human footprint, urbanization may be negatively affecting important apex predators.
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