Resighting data reveal weak connectivity from wintering to breeding grounds in a range-restricted and endangered long-distance migratory passerine

Abstract

Understanding migratory connectivity is fundamental to the ecology, evolution, and conservation of migratory species. The endangered Kirtland's Warbler (Setophaga kirtlandii) has a restricted breeding range in early successional jack pine (Pinus banksiana) forests with most of the population in northern Michigan and smaller subpopulations in Wisconsin and Ontario. Kirtland's Warblers spend the winter almost exclusively in the Bahamian Archipelago. Using a combination of visual searches and radiotelemetry, we relocated 89 Kirtland's Warblers on the breeding grounds that were captured and banded on two islands in the central Bahamas. We quantified the strength of migratory connectivity using a new metric "MC," and the Mantel test. We found that regardless of wintering island, Kirtland's Warblers intermixed heavily on the breeding grounds, having migrated to sites throughout the entire breeding range. Our estimates indicated weak connectivity between the wintering and breeding grounds, as might be predicted from a species that uses ephemeral, early successional habitat on both the wintering and breeding grounds. These results suggest that loss of habitat at a wintering site would have a diffuse effect across the entire population. The importance of a landscape approach to conservation of this species, long recognized in the breeding season and more recently emphasized on the wintering grounds, is supported by our findings. Les données de réobservation révèlent une faible connectivité entre les aires d'hivernage et celles de reproduction d'un passereau migrateur de longue distance, en voie de disparition et de répartition restreinte RÉSUMÉ. La compréhension de la connectivité des déplacements migratoires est fondamentale pour l'écologie, l'évolution et la conservation des espèces migratrices. La Paruline de Kirtland (Setophaga kirtlandii), en voie de disparition, a une aire de reproduction restreinte aux forêts de pins gris (Pinus banksiana) de début de succession, et le gros de sa population se trouve dans le nord du Michigan, avec de petites sous-populations fréquentant le Wisconsin et l'Ontario. Cette paruline passe presque exclusivement l'hiver dans l'archipel des Bahamas. À l'aide de recherches visuelles et de la radiotélémétrie, nous avons relocalisé sur les aires de nidification 89 Parulines de Kirtland qui avaient été capturées et baguées sur deux îles dans le centre des Bahamas. Nous avons quantifié le degré de connectivité des déplacements migratoires au moyen d'une nouvelle mesure dite « MC » et du test de Mantel. Nous avons trouvé que, peu importe leur île d'hivernage, les Parulines de Kirtland migrent aux quatre coins de l'aire de reproduction et se mélangent grandement sur les sites de nidification. Nos estimations ont indiqué une faible connectivité entre les aires d'hivernage et celles de nidification, comme on peut le supposer chez une espèce qui fréquente des milieux éphémères de début de succession, tant sur les aires d'hivernage que de nidification. Nos résultats montrent que la perte d'habitat su...

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