Using stable-isotopes in bird feathers to assess the benefits of local conservation actions

Natal dispersal, the movement from a natal site (place of birth) to a new breeding site, is probably the most important and least understood life history trait in wild animals. It is fundamental to the ecological understanding of landscapes, populations and organisms, and a necessary consideration when devising conservation plans. Despite the fact that natal dispersal (or lack thereof) drives population biology, colonization and range expansion, metapopulation and source-sink population dynamics, and the genetic structure in populations, we know very little about it. We know particularly little about natal dispersal in Neotropical migratory birds, many of which are high on conservation priority lists. Therefore, it has been difficult to assess the full impact of local conservation actions designed to benefit breeding populations of Neotropical migratory birds. Recent developments in stable-isotope techniques allow us to now use feathers to determine the origins of migratory birds. By studying the stable-isotope signature of feathers collected from the Neotropical migratory Prothonotary Warblers (Protonotaria citrea) that were newly recruited into local breeding populations in the Cache River watershed in Illinois, we can better assess the effectiveness of local conservation actions that increase the nesting success of birds (e.g. land acquisition and reforestation, wetland restoration), and measure the benefits of local conservation actions to the local breeding bird community. In collaboration with Dr. Keith Hobson, a world-renowned expert in stable-isotopes and animal migration, and with additional assistance from the Florida Museum of Natural History (Dr. Scott Robinson), this research addressed the questions: 1) Does local reproduction maintain local populations in a migratory species (warblers produced in the Cache return to the Cache to breed); and 2) to what extent are local populations maintained (“rescued”) by birds that are dispersing into the system from distant sources? The answers to these related questions have profound implications for how we evaluate the effectiveness of conservation actions.