PARENT SESSION
Oral Session # 17: Avian Ecology I.
Presiding: J Arnold
Tuesday, August 5. 8:00 AM to 11:30 AM, SITCC Meeting Room 103.
Tropical winter habitat limits reproductive success on the temperate breeding grounds in a migratory bird.
Norris, Ryan *,1, Marra, Peter 2, Kyser, Kurt 3, Sherry, Thomas4, Ratcliffe, Laurene1, 1 Department of Biology, Kingston, ON, Canada2 Smithsonian Environmental Research Center, Edgewater, MD, United States3 Department of Geological Sciences, Kingston, ON, Canada4 Department of Ecology and Evolutionary Biology, New Orleans, LA, United States
ABSTRACT- Isolating 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 for the first time that the reproductive success of a long-distance migratory bird is influenced by habitat quality thousands of kilometers away on tropical wintering grounds. For male American redstarts (Setophaga ruticilla), winter habitat quality influences arrival date on the breeding grounds, which in turn affects key variables associated with reproduction, including number of young fledged. Females occupying high quality winter habitat produce up to two additional young and fledge offspring up to a month earlier compared to females wintering in poor quality habitat. Differences of this magnitude are highly significant 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 provide fundamental evidence for the importance of understanding how periods of the annual cycle interact for migratory animals. Importantly, continued loss of tropical wintering habitat could have negative effects on migratory populations the following breeding season, minimizing density-dependent "buffer" effects on the breeding grounds and leading to further population declines. If conservation efforts are to be successful, strategies must, therefore, incorporate measures to protect habitat throughout the entire annual cycle in migratory animals.
Key words: migratory birds, carry-over effects, stable-isotopes, population limitation