Tropical winter habitat limits reproductive success on the temperate breeding grounds in a migratory bird.
Identifying the factors that control population dynamics in migratory animals has been constrained by our inability to track individuals throughout the annual cycle. Using stable carbon isotopes, we show that the reproductive success of a long-distance migratory bird is influenced by the quality of habitat located thousands of kilometres away on tropical wintering grounds. For male American redstarts (Setophaga ruticilla), winter habitat quality influenced arrival date on the breeding grounds, which in turn affected key variables associated with reproduction, including the number of young fledged. Based on a winter-habitat model, females occupying high-quality winter habitat were predicted to produce more than two additional young and to fledge offspring up to a month earlier compared with females wintering in poor-quality habitat. Differences of this magnitude are highly important considering redstarts are single brooded, lay clutches of only three to five eggs and spend only two-and-a-half months on the breeding grounds. Results from this study indicate the importance of understanding how periods of the annual cycle interact for migratory animals. Continued loss of tropical wintering habitat could have negative effects on migratory populations in the following breeding season, minimizing density-dependent effects on the breeding grounds and leading to further population declines. If conservation efforts are to be successful, strategies must incorporate measures to protect all the habitats used during the entire annual cycle of migratory animals.
Norris
D Ryan
DR
Department of Biology, Queen's University, Kingston, Ontario K7L 3N6, Canada. ryann@biology.queensu.ca
Marra
Peter P
PP
Kyser
T Kurt
TK
Sherry
Thomas W
TW
Ratcliffe
Laurene M
LM
D025041:Animal Migration; D000818:Animals; D002247:Carbon Isotopes; D003247:Conservation of Natural Resources; D004777:Environment; D008098:Litter Size; D008297:Male; D009864:Ontario; D011157:Population Dynamics; D012098:Reproduction / Q000502:physiology*; D012621:Seasons; D020308:Songbirds / Q000502:physiology*; D013997:Time Factors; D014329:Tropical Climate
D002247:Carbon Isotopes