Date of Award:

5-1-1997

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Committee Chair(s)

Paul G. Wolf

Committee

Paul G. Wolf

Committee

Edmund D. Brodie Jr.

Committee

C. Anna Toline

Abstract

Extra-pair fertilization, a secondary breeding strategy, was detected in the eastern kingbird (Tyrannus tyrannus) using multi-locus DNA fingerprinting. I assessed the genetic parentage of 20 broods in a population of kingbirds in central New York. Two DNA probes were used to test for exclusion of nestlings as true offspring of one or both social parents. Band-sharing coefficients and the number of novel bands were used to discern which parent was not a first-degree relative of the nestling in question. No cases of conspecific brood parasitism or quasi-parasitism were documented. However, extra-pair paternity was found to be very common, despite the prediction that cuckoldry would be uncommon in a socially monogamous, territorial, and solitary bird. Of the 20 families analyzed, 60% (12 / 20) of nests contained at least one extra-pair young, and 41% (26 / 64) of all nestlings analyzed were sired by extra-pair males. Cuckoldry was more common in the nests of experienced females than in the nests of inexperienced females (Fisher's exact test, P < 0.05). These data were consistent with female control of extra-pair copulations and suggested that females may be seeking extra-pair matings for genetic benefits. Egg physiognomic measurements have the potential to be used in identifying instances of conspecific brood parasitism in eastern kingbirds. I quantified egg size and spotting patterns by taking direct measurements in the field and by analyzing digitized computer images of photographs of eggs. Females were repeatable (r > 0.64; F-ratio > 5.04; df = 24,32) for all variables used in subsequent analyses. Two principal components were derived from the variables measured. Principal component 1 described the amount of pigmentation and spot size, and principal component 2 described egg size and the number of spots. The within-clutch variance for these two principal components was significantly less than the among-clutch variance (paired t-tests, p < 0.05). Furthermore, when clutches were similar with respect to one principal component, they tended to be very different with respect to the other principal component. Because there were no instances of brood parasitism in this population of kingbirds, I was unable to test the prediction that parasitized nests would have significantly different variances in egg physiognomic measurements than unparasitized nests. Additionally, as predicted, the egg physiognomy of cuckolded nests was not significantly different from non-cuckolded nests.

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