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Parrots are among the most endangered birds in the world, owing to the international pet trade, and habitat degradation. Grey Parrot Psittacus erithacus, the most traded wild-caught species, has suffered a steep decline across its vast African range. This PhD investigates Grey Parrot’s ecology to understand the mechanisms by which harvest and habitat loss affect populations. The island of Príncipe was chosen as a study area owing to its healthy Grey Parrot population, its tradition of parrot harvest and the disturbed-to-pristine range of habitats. Parrot densities were exceptionally high (mean±SE: 53±3 parrots km-1), and their distribution within the island was shown to change significantly between pre- and post-breeding season. The presence of nest tree species was the best predictor of densities in the former (F = 2.99, p = 0.07), while slope and food tree species were in the latter (F = 3.0, p < 0.05 and F = 8.04, p < 0.01). Variation in habitat use across seasons highlights the importance of opportunely timed surveys, and the need of preserving a matrix of habitats. Three simple and inexpensive methods were tested, which may be useful where more precise methods cannot be used. Simple encounter rates were shown to be a workable proxy for actual densities: a relationship was found between the two (R2=0.8, df=9, p=0.01). Long watches proved to be far less accurate and suitable only in limited cases (i.e. enough vantage points overlooking small areas and numerous encounters). Counts along flyways were suggested to be a good monitoring method, although further testing is required. Nest densities were found to be very high (mean±SE: 16.8±7.9 and 72.4±26.2 nests km-2 in secondary and primary forest respectively) compared to those elsewhere. The habitat characteristics measured didn’t affect productivity, suggesting that cavity characteristics may be more important. The best demographic data available on the species, were used to build a Population Viability Model to investigate its population dynamics in the face of harvest and habitat loss. In Príncipe, Grey Parrots were shown to have increased rapidly after a trade ban was put in place, highlighting the recovery potential of the species. Harvest alone was shown to be harmless only when small quotas (e.g. 600 chicks year-1) are yielded from large populations, while habitat loss lowered the predicted maximum population size. The interaction of these threats can be much more unpredictable. The effects of harvest are worsened if poorly regulated or techniques that include the harvesting of adults are used. Extinctions were predicted to occur with significant delay (≥40 years), and the conservation implications were discussed. Finally, the contribution of this thesis to the understanding of Grey Parrots ecology and conservation is highlighted and research priorities identified.

In Ghana, many large avian frugivores face very serious threats, including habitat loss, hunting, and capture for the pet trade. However, basic ecological information is lacking for most species including the heavily-traded Grey Parrot Psittacus erithacus. The aim of my PhD was therefore to investigate the current distribution, abundance and ecology of Grey Parrot and other large frugivores to help inform their future conservation. I conducted surveys for twenty species of pigeons, parrots, turacos and hornbills in forty-two 10 km × 10 km survey squares in southwest Ghana. Only two species, West African Pied Hornbill Lophoceros semifasciatus and African Green Pigeon Treron calvus, were recorded in most survey squares. The most restricted and rare species included large-bodied species such as Great Blue Turaco Corythaeola cristata, Yellow-casqued Hornbill Ceratogymna elata and Black-casqued Hornbill C. atrata. Canonical Correspondence Analysis showed that large hornbills were especially restricted to large forest reserves with low anthropogenic disturbance. I then used Maxent to predict more precisely the distribution of the frugivores across Ghana, and identify their responses to predictors such as land cover types, enhanced vegetation index (EVI), human population density, and climate data. Frugivores showed varying associations with Ghana’s large forest reserves, with Afep Pigeon Columba unicincta, Great Blue Turaco, and Black Dwarf Hornbill Tockus hartlaubi among the most restricted. Most species had highest occurrence probabilities in the southwest of the country. The main driver of distributions was land cover type, with forest habitats preferred in 90% of species. Differences in human population density and EVI were seldom important. The large southwestern forest reserves are key sites for Ghana’s frugivores, and it is crucial that they are adequately protected and managed. Grey Parrot is believed to have undergone rapid population decline, yet there are almost no quantitative data properly supporting this from anywhere within its huge range. I reviewed its historical abundance across Ghana, undertook targeted searches across the country’s forest zone, repeated counts at 22 parrot roosts first performed two decades ago and gauged around 900 people’s perceptions of the decline and its causes. In over 150 days of fieldwork, just 32 groups were recorded. Encounter rates were 15 times lower than those from the early 1990s. No active roosts, i.e. roosts in current use, were found, and just a handful of birds seen near three roosts that each harboured 700–1200 birds two decades ago. Interviewees stressed the importance of very tall trees of commercially important timber species for nesting and roosting. Ghana has lost 90–99% of its Grey Parrots since 1992, and there is no evidence that, away from one or two localities, declines are less severe anywhere else in West Africa. Despite declines, Grey Parrots paradoxically remain reasonably widely distributed. I developed multiple historical and current Maxent models for the species based on various presence data sources: field surveys from the early 1990s and 2012–14, records from the Global Biodiversity Information Facility, and interview data. Models of historical distribution showed high suitability over much of the study area. Current distributions were predicted to be much more patchy, with large areas unsuitable, but with high suitability in the extreme south/southwest. Historically, Grey Parrot distribution was correlated most strongly with high rainfall, while current distribution is more closely linked with land use. Levels of exploitation of Grey Parrots have been unsustainable and regulation of the trade through quota schemes and enforcement of trade embargoes needs to be strengthened. Ghana should also reintroduce shade cocoa agriculture to improve habitat quality for the Grey Parrot and other frugivores.

Evidence of cognitive complexity in birds has led to the recognition that mammalian and avian species likely evolved comparable high-level cognitive capacities independently. One of the most significant findings that have emerged from this area of study is the identification of a key social trait that is found in species deemed to be intelligent – the presence of long-term, high-quality partnerships. Amongst birds, parrots (along with corvids) have shown relatively high levels of both cognitive and social complexity. However, relatively few parrot species have been the subject of empirical investigation. The original research presented in this thesis explores social behaviour and cognitive capacity in orange-winged Amazons (Amazona amazonica) and blue and gold macaws (Ara ararauna). Observational research findings revealed evidence of high-quality relationships in both species, and while levels of affiliative investment were similar in orange-winged Amazons (OWAs) and blue and gold macaws (BGMs), some potentially meaningful between species differences were found in courtship feeding, allopreening, and social tolerance. Experimental research findings revealed evidence of inhibitory control in both species (as measured by performance on a transparent cylinder task), though OWAs performed significantly better than BGMs on test trials. Social learning capacities were also found in OWAs through an open diffusion experiment. Both species showed poor performance in a means-end task, yielding no evidence of causal understanding. Birds also had difficulty acquiring the loose string task, which was aimed at testing cooperative problem solving. Poor performance of both OWAs and BGMs on these tasks is believed to have been primarily due to non-cognitive factors (e.g., motivation, motor difficulty of task). Affiliative investment and performance on the social learning task were found to be positively correlated in BGMs and there was some indication that individual variation in boldness may have been associated with inhibitory task performance in BGMs.

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Central place foragers, such as territorial hummingbirds, feed from resources that tend to be constant in space and to replenish with time (e.g. nectar in flowers). The ability to remember both where and when resources are available would allow these animals to forage efficiently. Animals that feed at multiple locations would also benefit from forming routes between these multiple locations. Hummingbirds are thought to forage by repeating the order in which they visit several locations following a route called a “trapline”, although there are no quantitative data describing this behaviour. As a first step to determining how and if wild free living hummingbirds forage by traplining, I decomposed this behaviour into some of its key components. Through five field experiments, where I trained free-living hummingbirds to feed from artificial flowers, I confirmed that territorial hummingbirds will, in fact, trapline. Birds will use the shortest routes to visit several locations and will prioritize those locations that are closest to a usual feeding site. Additionally, even though hummingbirds can learn to use temporal information when visiting several patches of flowers, the spatial location of those patches has a larger influence in how these birds forage in the wild. Since male and female hummingbirds were thought to forage differently I also tested whether there were sex differences in the types of cues they use when foraging. Contrary to expectation, female hummingbirds will also use spatial cues to relocate a rewarded site. Using the foraging ecology of rufous hummingbirds to formulate predictions as to what information these birds should use has lead me to discover that these birds forage in a completely different way than previously thought.