In social systems, the distribution of reproduction among group members is termed reproductive skew. This study was intended to address the issues of reproductive skew within the communally breeding smooth-billed ani employing genetic data to complement behavioural data. The aims of the study were: 1) to develop smooth-billed ani specific DNA markers to be used in the assessment of parentage 2) to determine parentage of buried eggs and surviving offspring to assess whether a reproductive skew pattern is seen 3) to comment on adult relatedness within smooth-billed ani groups. Smooth-billed ani microsatellite DNA sequences were isolated and characterized for use in a parentage/kinship analysis. Lambda Zap Express was used to construct a library of recombinant phage which was screened with TG and AAT probes. Five loci were characterized with between 4 and 9 alleles with heterozygosity values ranging from 0.538 to 0.840. The combined total exclusionary power of the five loci was 0.8869. Offspring loss due to egg destruction in the form of burial has been observed in smooth-billed anis. The issue of reproductive skew as a result of egg burial was addressed by estimating parentage of offspring both buried and remaining in the incubated clutch using 5 species specific microsatellite DNA markers. Evidence for an egalitarian system exhibiting very low skew was found. The significant factors affecting the potential for bias were laying order, laying timing and the number of breeding females. The relatedness of members within a social group may affect the amount of reproductive skew observed. Adults within nesting groups were tested for evidence of relatedness using the pedigree analysis program KINSHIP. Ten percent of dyads showed significant relationships. Low incidence of relatedness provided evidence that smooth-billed ani groups do not contain a large number ofyoung remaining at the natal nest nor was there evidence that regular dispersing within sibling units occurs. There was some evidence that a young male remained on his natal territory while a young female dispersed to a neighbouring territory. Low relatedness between adults and very low reproductive skew were consistent with the prediction of an egalitarian system / Thesis / Master of Science (MS)

The communal breeding system of the smooth-billed ani (Crotophaga ani) was studied at two wildlife refuges in southwest Puerto Rico. Groups ranged in size from 2 to 9 adults, and communal clutches ranged in size from 11 to more than 25 eggs. Microsatellite DNA loci were isolated and used to examine the mating system and the extent of reproductive skew in individual groups. Loci were also screened in guira cuckoos (Guira guira) to examine the relationships suggested by Quinn et al. (1994). In the four focal smooth-billed ani groups, I found suggestions of monogamy, polygamy, and incidents of intraspecific brood parasitism. In all groups, incubated clutch size and microsatellite data indicate that subordinate females are gaining some reproductive success. At one nest, evidence suggested a decrease in the intensity of reproductive skew between successive nests. Although the data are limited, they suggest that alternative strategies to monogamy may be more prevalent than previously believed, and that reproductive skew may be affected by the availability of limiting resources within the breeding season. / Thesis / Master of Science (MS)