PARENT SESSION
Contributed Oral Session 18: Avian Communities and Populations
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 524 C, Level 5, Palais des congrès de Montréal

Long-distance dispersal and source-sink dynamics in songbirds.

Tittler, Rebecca^*,1, Fahrig, Lenore¹, Villard, Marc-Andre², ¹ Geomatics and Landscape Ecology Lab, Ottawa, ON, Canada² Canada Research Chair in Landscape Conservation, Moncton, NB, Canada

ABSTRACT- Although much research has focussed on identifying source and sink populations among songbirds, there is a lack of information on the distances over which source-sink dynamics occur between populations. Such knowledge would allow us to predict the scale over which management of a source might affect dependent sinks. Without such knowledge, the large-scale effects of even small changes in habitat may be difficult to predict. Since sources and sinks must be linked by dispersal, it is critical to gain insight into the extent of these movements. Unfortunately, there is a lack of reliable information on dispersal distances. We therefore present a novel approach to the study of source-sink dynamics and dispersal. If source-sink dynamics occur consistently over time between populations, these populations must not only be linked by dispersal, but by asymmetrical dispersal, predominantly from the source to the sink. Consistent asymmetrical dispersal between populations will produce time-lagged correlations in abundance between pairs of populations separated by the dispersal distance. We asked (1) Is there evidence that asymmetrical dispersal and therefore source-sink dynamics occur consistently over time between pairs of songbird populations? and (2) Over what scale(s) does this occur? Using the North American Breeding Bird Survey database, we found evidence of asymmetrical dispersal and source-sink dynamics for populations of several species of declining neotropical migrant songbirds, indicating that individuals of these species typically disperse from 20 to 80 km, depending on the species. These distances are generally an order of magnitude longer than previously thought. Preliminary analyses also indicate a possible link between these typical dispersal distances and species-specific body sizes. These results also provide evidence that source-sink dynamics likely occur over these distances. Conservation strategies for these species must therefore be designed at correspondingly large scales.

Key words: asymmetrical dispersal, source-sink dynamics, North American Breeding Bird Survey, long-distance dispersal