Characterization of dispersal and reproductive strategies in the eastern phoebe (Sayornis phoebe)

Amanda Susan Allen Beheler, Purdue University

Abstract

Reproductive strategies in birds are much more complex than previously imagined. In this study, I examined three different aspects of reproduction in a migrant passerine, the Eastern Phoebe (Sayornis phoebe). I investigated the temporal and energetic variation in reproductive effort (clutch size) and nesting success (numbers of eggs hatched, numbers of young fledged, and proportions of young fledged) according to female nesting type and brood number, the level of breeding site (territory and nest) fidelity and mate fidelity within and between years, and the presence and frequency of extra-pair young in first and second brood nests. I also developed a suite of 5 Eastern Phoebe microsatellite loci for use in molecular genetic analyses. Eastern Phoebes in this study had extremely high nesting success. Although clutch size ranged from 2 to 6 eggs, little variation was observed and 93% of all nests had complete clutches of 4 or 5 eggs. Nests initiated in the early season had significantly larger clutches and fledged more young than nests initiated in the late season. Late-season, 1-brooded females laid the smallest mean first brood clutch of all female types. Declines in clutch size and numbers of young fledged were found between the first and second broods of 2-brooded females but not between consecutive clutches laid by renest females. Breeding site (i.e. territory and nest) and mate fidelity were extremely high both within and between years. Eastern Phoebe adults rarely dispersed to new territories, but after an initial nest failure, they were more likely to change nests within a territory for their second breeding attempt. Males were more likely to change territories between years; however, the distance dispersed between territories did not differ between the sexes. Divorce was uncommon and not influenced by gender or previous reproductive success. Although the majority of Eastern Phoebe pairs were both socially and genetically monogamous within a breeding season, 17.2% of all families had extra-pair young in at least one brood and I found 2 instances of apparent intraspecific brood parasitism. I also discovered that second broods were more likely to contain EPY than first broods.

Degree

Ph.D.

Advisors

Rhodes, Purdue University.

Subject Area

Forestry|Ecology|Genetics|Zoology

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