Understanding the impact of hurricanes on migratory birds: a scale dependent approach.
Diehl, Robert *,1, Moore, Frank1, Buler, Jeffrey1, Barrow, Wylie2, 1 University of Southern Mississippi, Hattiesburg, Mississippi2 USGS National Wetlands Research Center, Lafayette, Louisiana
ABSTRACT- Hurricane season in the North Atlantic coincides with the height of fall bird migration, and the storms themselves frequently occur where bird migration is at its peak over the Gulf of Mexico and western Atlantic. Although we know little about how hurricanes impact birds during migratory passage, this overlap in space and time suggests hurricanes, as agents of selection, have not resulted in the evolution of migratory routes that avoid regions of hurricane activity altogether. Such speculation on the evolutionary basis for broad patterns of migration observed today would benefit from better understanding the proximal impact of hurricanes on migrating birds. For example, hurricanes may suspend or delay migratory passage, or temporarily promote migration along more western longitudes that avoid potentially hazardous trans-water routes and exploit favorable northerly winds west of storms. These altered migration patterns in turn lead to broad redistributions of birds in the landscape during stopover. Habitats often characterized by relatively high stopover densities, such as coasts, may be avoided, reducing the impact of hurricanes on birds directly. After a hurricane passes, coastal vegetation that suffers from inundation or wind damage may not support an adequate food base for migrating birds. Consequently, birds may be slow to return to such habitats, even across seasons if the effects are lasting. Clearly, the extrinsic (to habitat) influence of hurricanes on large scale flight and distribution patterns is linked to factors intrinsic to habitat that effect individual birds during migration. In keeping with the inherent relationship between these extrinsic and intrinsic factors, research on the effects of hurricanes on migrating birds should adopt a hierarchical approach to making predictions about patterns at different spatial and temporal scales. Such research should improve understanding of the hazards that birds face during migration and the resulting consequences for the long-term survival of species.
Key words: bird migration, weather, hierarchical approach
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