The primary objective of the study was to determine why established females tolerate new females that join their breeding group and lay eggs in their nest. Previous work on this population has shown that females suffer a cost of joint-nesting in the form of lowered hatching success. Therefore, we would expect female pukeko to attempt to disrupt the reproductive efforts of their co-nesters by ejecting their eggs from the joint nest. Two hypotheses might explain why this does not happen. The "peace incentive" hypothesis states that females would forego egg destruction to avoid retaliatory behaviour by the other female. Alternatively, females might not destroy the eggs of co-nesters because they cannot discriminate between their own and another female's eggs. To test between these, we experimentally removed the eggs of one of the females from a number of joint nests. In all S(Wen cases for which we have data on the post-removal behaviour of the females, the robbed female showed no response to the disappearance of her eggs and continued to incubate the clutch. In addition, we added eggs to eight single female nests. Again, the single females showed no sign that they could distinguish between the foreign eggs and their own. The foreign eggs were not buried, ejected, or destroyed, nor were they moved preferentially to the outer perimeter of the clutch. To perform the egg removal experiments, I needed to correctly group joint clutches of eggs into maternal sib-groups. I evaluated two methods of doing this, one relying on qualitative observer assessment and the other on statistical techniques. I determined genetic maternity using DNA fingerprinting. Qualitative assessment was more effective than statistical techniques for identifying the maternity of eggs. Such an approach may be a useful alternative to expensive and time-consuming molecular genetic techniques for measuring reproductive skew in joint-nesting birds. Predation rates on pukeko nests at our study site during the 1998/99 nesting season were significantly higher than they had been in previous years (1990-1995). In the intervening years, the local rabbit population crashed as the result of two rabbit control measures: poisoning and rabbit haemorrhagic disease (RHD). We hypothesised that the increase in predation rates was due to rabbit specialist predators seeking out alternative prey after the crash in rabbit populations. Such a scenario is of grave concern to wildlife managers in many areas of New Zealand where rabbits are abundant and threatened native bird species are already under extreme pressure from introduced predators. / Thesis / Master of Science (MS)

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

I investigated the maternal effects that take place in a joint-nesting bird: the smooth-billed ani. Female anis were shown to respond to increasing group size by increasing the number of eggs produced per capita, by tossing and burying more eggs per capita, and by taking longer to reach the dedicated incubation phase. These results support the hypothesis that females respond to increased egg laying competition by trying to skew the contents of the final incubated clutch of eggs in their own favor. I showed that in ani groups, yolk testosterone and estradiol deposited by females in eggs increased from early- to late-laid eggs. Increases in yolk steroid levels over the laying sequence may function to mitigate the disadvantage of being a later-hatched chick. This maternal influence may not be a mere reflection of a female's hormonal status as female plasma circulating levels of testosterone and estradiol did not vary in the same direction as yolk hormone profiles. I showed that yolk corticosterone levels, an indicator of maternal physiological stress, increased with laying order in multi-female groups, but not in single-female groups. Results suggest that laying females experience higher levels of stress in multifemale groups. The above results suggest that communal life in anis generates competition and egg production waste that likely reduces short-term per capita reproductive benefits. Female anis can vary egg quality via deposition of hormones in eggs, and also lay eggs of different sizes. I showed that circulating plasma testosterone levels were higher in nestlings with better begging abilities. Furthermore, nestlings hatched from eggs laid late in the laying sequence had better begging abilities. These results suggest that testosterone is an important controlling mechanism of begging behaviour, and that female testosterone depositions in eggs rave long lasting effects on offspring development and behavior. / Thesis / Doctor of Philosophy (PhD)

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)

Group living is a widespread social system among animals. Within these groups, decisions on interactions between individuals can be facilitated through knowledge about individual identity and kinship. Individual identity allows for the recognition of individuals from past interactions and thus, information on likelihood of reciprocity and group-membership can be gained. The benefit for cooperative interactions, specifically, increases with the level of relatedness between the helper and the recipient. Thus, knowing who is kin, is an essential ability among group-living species and remembering individual identity helps to maintain long-term relationships and inform future decisions. Kin recognition can be facilitated through temporal and spatial overlap (i.e. familiarity) or through phenotypic-templates (i.e. phenotype matching). The goal of this thesis was to explore recognition in the joint-nesting pūkeko (Porphyrio melanotus melanotus). For the first portion of this thesis (Chapter II), I tested for evidence of phenotype matching in pūkeko using a cross-fostering experiment. Comparing survival and growth between fostered and non-fostered offspring, I provide evidence that pūkeko do not use phenotype matching as their mechanism for kin recognition. In Chapter III, I show that pūkeko chick distress calls may have an individual and group signature. I found variation in the vocal parameters between individual chicks and social groups. I also tested for response of adults towards chick distress calls of their own group. Using a playback-choice experiment, I report a biased response of adult pūkeko towards the distress call of their own group's chicks rather than the call of a distressed chick from a foreign chick. / Thesis / Master of Science (MSc) / Kin recognition is an essential ability for social species. Knowing whom is kin can help inform decisions on cooperation and conflict. I explored whether the joint-nesting pūkeko use familiarity or phenotype matching to recognise cross-fostered offspring. I experimented to determine if adult pūkeko can recognise the distress vocalizations of chicks in their group. I found no evidence that pūkeko use phenotypic templates to recognise cross-fostered chicks as non-kin. However, adult pūkeko showed a bias in response towards the distress calls of their own versus unfamiliar chicks. Individual chick distress calls, while variable from day-to-day, show group-specific similarities.