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)

Abstract Not Provided / Thesis / Master of Science (MSc)

Territorial behaviour is exhibited in cooperative breeders. The quality of defended territories can vary, and high-quality sites, which enhance fitness, should be used preferentially over poorer-quality sites. This study was intended to address issues of territory quality within the plural breeding, joint-nesting, smooth-billed ani (Crotophaga ani). I tested the communal joint-nesting threshold hypothesis, which posits that independent pairs will pay the price of group living if compensated by acquiring a superior territory. My results quantified differences in territory quality in terms of time of first breeding and chances for re-nesting or second-brooding. Per capita territory quality correlated negatively with group size, in conflict with the communal joint-nesting threshold hypothesis. Another hypothesis to explain communal behaviour is the habitat saturation hypothesis. This postulates that offspring remain in their natal territory and delay reproduction because of a local absence of suitable breeding habitat. I tested the habitat saturation hypothesis, which was developed to explain the evolution of group living in cooperatively breeding birds. I compared occupied ani territories with vacant sites, using eight ecological variables that may be important to the fitness of a group. In addition, I compared occupied territories with sites that were occasionally occupied. I did not find the habitat of our population of smooth-billed anis to be saturated. Some sites were never occupied because there are territory characteristics that presumably limit breeding. In contrast with expectations of habitat saturation, there were suitable sites available for breeding that were not in use. Results from both hypotheses presented suggest that there are not obvious group-living benefits and that one must consider other explanations for the evolution and maintenance of this system. / Thesis / Master of Science (MS)

Sexual selection has been investigated in many different systems but information is lacking in joint-nesting species. Both sexual dimorphism and possible signals of quality were explored in this study for a joint-nesting plural breeder, the smooth-billed ani (Crotophaga ani). Sexual dimorphism can be examined for a species in an attempt to reveal particular traits that might be under sexual selection and the strength of sexual selection on them. In mate choice decisions, sexually selected traits may be used by the choosy individual to assess the quality of potential mates. These honest traits need to reveal the condition and genetic quality of the individual accurately. For example, it has been proposed that plumage colour reveals condition, and more specifically parasite resistance in birds. This study explores sexual size dimorphism and dichromatism in smooth-billed anis, as well as the ability of their feather colour to reveal body condition (measured as residuals from a regression of mass versus body size), body size, and parasite numbers. Additionally, because anis are group living birds, this study investigated whether group size had an effect on parasite numbers. Anis from a population in southwestern Puerto Rico were measured for size, their feathers were collected and analyzed using a spectrometer, and ectoparasites were collected by dustruffling. For all size traits measured, males were significantly larger than females. Males also had more exaggerated bill depths (relative to body size) than females. There were no differences between the sexes for all colour morphometries, except tail saturation; females had more saturated tails than males. While no decisive conclusions can be drawn as to why the dimorphic traits are different between males and females, sexual selection may have played a role. The relationship between log10 average lice numbers per group and group size was positive, but not significant. In male smooth-billed anis, plumage colour was not related to lice or mite numbers, or body size and body condition. Plumage colour was also not related to body condition and size in females. Additionally, ectoparasites did not have an effect on male body condition. Plumage may not only be an inaccurate signal of parasite resistance or body size and body condition in the smooth-billed ani, but ectoparasites may not even have a negative effect on their host. The inability to find significant results may have been affected by other factors, such as feather wear and the age of individuals. These results warrant a more detailed look into the social behaviour of the group-living smooth-billed ani. / Thesis / Master of Science (MSc)