The potential role of hurricanes in the creation and maintenance of Kirtland's warbler winter habitat in the Bahamian Archipelago.

Abstract

The threatened migratory Kirtland’s Warbler (KW, Dendorica kirtlandii) breeds exclusively in Michigan and overwinters nearly exclusively in the Bahamas Archipelago, where little is known of its winter habitat. Previous observations and our own studies indicate that KWs routinely use early successional or regenerating shrubby habitats on Eleuthera. Our preliminary results suggest that wintering KWs readily shift locations on Eleuthera as they track food abundance (especially fruit) that waxes and wanes at different sites as the winter proceeds. The use of disturbed sites and a pattern of winter movements that allows opportunistic use of the richest available food patches are consistent with a disturbance-adapted foraging strategy. Although all of our KW capture sites (N = 77) on Eleuthera show evidence of previous human disturbance resulting from agriculture or building construction, we hypothesize that the early seral stages of secondary broadleaf (coppice) habitats used by the warbler could also be produced by hurricanes. By reducing or eliminating canopy of tall coppice, hurricanes stimulate understory growth, which favors regeneration and colonization by fruiting shrubs. Moreover, hurricane storm surges in low-lying coastal areas may create patches for colonization by early successional plant species, some of which may be used by KWs. In addition, hurricanes may prolong the “life” of existing KW sites by setting back or delaying succession or regeneration. New growth after hurricanes may also result in increased abundance of arthropods and fruits consumed by KWs. Hurricanes occur with sufficient frequency in the archipelago to be an integral part of the natural disturbance regime and were likely an important natural disturbance factor in presettlement times. However, no studies of KWs have yet been conducted in sites severely damaged by hurricanes. Therefore, this hypothesis remains to be tested, especially because of its conservation importance for understanding how KW winter habitats are produced.

Citation

Wunderle, Jr, Joseph M.; Currie, David; Ewert, David N. 2007. The potential role of hurricanes in the creation and maintenance of Kirtland''s warbler winter habitat in the Bahamian Archipelago. The 11th Symposium on the Natural History of the Bahamas :121-129