|HOME SCHEDULE AUTHOR INDEX SUBJECT INDEX|
Source sink dynamics of American redstarts in an agricultural landscape.
Hannon, Susan*,1, 1 Dept of Biological Sciences, Edmonton, AB, Canada
ABSTRACT- The major goal of this project was to complete the seventh year of a long-term program that monitors the reproductive success of American redstarts in 21 clusters in an agricultural area of Alberta. Clusters that had the highest probability of being reproductive sources were in larger woodlots that were more isolated from other woodlots and from farms and had fewer alternative cowbird hosts. We determined whether redstarts can recognize whether a patch has a high probability of being a reproductive source or sink. To test this we monitored settlement times of males and females in spring and found that redstarts were not settling in source clusters first, suggesting that the cues they use to settle are not related to the ultimate reproductive success in the cluster. Second, we wished to determine if a redstart settled in a sink, would it switch to a source the next year. We found that birds that switched clusters between years were equally likely to have bred in a source or a sink the previous year, but that birds that had failed to produce young the previous year were more likely to switch clusters. However, they had an equal probability of switching to a source or sink, again suggesting that they cannot recognize a source patch. Several males made out-of-cluster movements, and some had nests in more than one cluster. We are currently analysing DNA from blood samples taken from 26 complete families to assess the amount of extra-cluster paternity.
Key words: forest fragmentation, sink, redstarts, source