Hurricane, Habitat Degradation, and Land Loss Effects on Brown Pelican Nesting Colonies

Abstract

Walter, S.T.; Carloss, M.R.; Hess, T.J., and Leberg, P.L., 2013. Hurricane, habitat degradation, and land loss effects on Brown Pelican nesting colonies.Nesting colonies of coastal avifauna are perennially threatened by hurricanes, land loss, and environmental contamination. To understand how nest substrate and habitat availability influence reproductive success of Brown Pelicans (Pelecanus occidentalis), we monitored 802 nests and quantified vegetation cover on two barrier islands in Louisiana from 2008 to 2010. In 2008, Hurricanes Gustav and Ike caused habitat degradation and land loss at our study sites and thus allowed comparison of pelican productivity in pre- and post-hurricane conditions. As habitat availability changed across years and islands, pelicans shifted from nesting in woody vegetation, to grasses, forbs, and bare ground. More chicks that survived until the age of 3 to 4.5 weeks old were from higher nests, and the loss of woody vegetation might have elicited colony abandonment. Habitat reduction was attributed to hurricane-induced erosion, and shoreline retreat was an average 5.5 times (range 3.3 to 11) greater than regional rates from 1887 to 2002. Furthermore, land loss (16% to 99% of vegetated regions) was restricted to areas without protective breakwaters. In addition to the effects of habitat decline on pelican reproduction, contamination by the Deepwater Horizon oil spill might have further decreased nest success. Large and productive seabird colonies can be rapidly degraded by both human and natural disturbance, making amelioration of such threats a management priority.