| In this thesis, I examined several aspects of extrapair paternity in tree swallows (Tachycineta bicolor). I used radio-telemetry to follow the movements of individual female tree swallows during the pre-laying and laying period. Using triangulation techniques, I determined first and last known locations of individuals in the morning and evening, respectively. My results indicated that individuals varied in their movement patterns, with some females routinely roosting away from the nestbox grid, while others were rarely detected away from their nestbox. I also found a trend for a decrease in movement during the laying period as compared to the pre-laying period.;Next, I used data from 11 hypervariable microsatellite loci on 99 tree swallow families collected over a period of five years to test the genetic compatibility hypothesis in this population. I found that 82% of all females produced extrapair offspring, and 47% of all young were the result of extrapair copulations. I determined that extrapair offspring were significantly more heterozygous than their withinpair nestmates, a finding that is in accordance with the genetic compatibility hypothesis. Contrary to my prediction, I found no difference in a female's relatedness to her social mate compared to her relatedness to her extrapair mate(s). However, as I was able to identify the sires of only 50% of the extrapair offspring, the sample sizes for this test were low and I may not have had enough power to detect a difference. Interestingly, although social pair relatedness values were not correlated with the presence of extrapair offspring, I did find that pairs that did not produce any extrapair offspring had significantly lower pairwise relatedness values than social pairs that had at least one extrapair offspring. Finally, I examined mate choice and patterns of paternity at the individual level. I used estimates of repeatability to test if levels of extrapair offspring present in a nest were consistent among breeding attempts for individuals mated to new social partners. I found that females were not consistent in the proportion of extrapair offspring produced, which is not surprising if females are making their extrapair mating decisions based on characteristics of their social mate. Most interesting was the finding that males, mated to different females, also did not have a consistent proportion of extrapair offspring in their nests, suggesting that traditional 'good genes' hypotheses cannot explain extrapair mating in this population of tree swallows. |
