Geographic position and landscape composition expl

Authors: Jill M Lafleur Jeffrey J Buler Frank R Moore

Publish Date: 2016/03/26

Volume: 31, Issue: 8, Pages: 1697-1709

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Abstract

We used weather surveillance radars to measure reflectivity of birds aloft at onset of nocturnal migratory flights and estimate bird stopover densities during four springs 2009–2012 for 67 million ha along the GOM We aggregated bird densities to one longitudinal degree and 3 km of proximity to coastBoosted Regression Tree models revealed that stopover density was related to year longitude proximity to coast and amount of hardwood forest cover in the landscape Average longitudinal patterns supported previous studies of broadscale transGulf migrant arrivals with highest density in Louisiana 92–93°W and lowest in Alabama 88–89°W Florida 83–84°W supported a second peak in migrant density suggesting an eastern transGulf route or contribution from transCaribbean migrants Longitudinal patterns in migrant distributions varied strongly between years and appear generally related to variability in GOM wind patterns Densities increased with proximity to coast highlighting constraints on migrants to travel inland especially in Florida’s panhandle Despite this density was positively related to amount of forest cover more steeply along the immediate coastWe thank Jaclyn Smolinsky for assistance with radar data processing Funding to support this research was awarded in part by a grant from the USGS Science Support Partnership Program and provided in part by the University of Southern Mississippi We acknowledge and are grateful for the support of the USGS Gulf Coast Joint Venture and constructive comments from two anonymous reviewers

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