Abstract

Tachycineta bicolor, the tree swallow, is a socially monogamous bird that practices extra-pair paternity, an event where females seek out mates different from their residential partner. Benefits of extra-pair paternity include increased sexual selection and higher genetic diversity among offspring. This behavior is not uncommon among bird species, especially those that are migratory. Tree swallows are typically residents in Canada, the central United States, and parts of Mexico, but the species has recently begun to expand the southern edge of their range. There is interest in whether this shift is associated with differences in other behaviors, specifically extra-pair paternity. It was hypothesized that the rate of extra-pair paternity in this new population of tree swallows would be similar to that in other tree swallow populations in the typical breeding range. To conduct this experiment, DNA was extracted from bird feathers of 82 tree swallows from seven different nest boxes around Beaver Lake (Asheville, North Carolina). PCR was used to amplify two microsatellite loci, PPi2 and LTMR6, from 23 individuals from five nests. Successful PCR products were sent out for fragment analysis. Fragment sizes at each locus were determined via Geneious 2019.0.4TM, and GERUD 2.0TM was then used to predict the potential genotype for the maternal and paternal parent of each nest. Results so far indicate that this population has reduced rates of extra-pair paternity. Seeing a major change in this population, like mating differences, could help explain other behavioral changes in the species, including the unusual shift in the tree swallows’ breeding range.

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