The detrimental effects of inbreeding are well known, and they have been shown to be associated with lower levels of reproductive success, higher levels of parasitism and differences in disease susceptibility. To better understand large fitness differences between morphs in the colour polymorphic common buzzard, Buteo buteo, we investigated differences in the levels of internal relatedness between morphs. As the common buzzard mating system is non-random and the light and dark morph individuals are less abundant than the intermediates, it could be the case the extreme colour morph individuals are more inbred. However, no differences were found in levels of inbreeding. In birds, the physiological and behavioural consequences of colour polymorphisms are not widely known. Here we used an experiment to investigate the effect of this melanin-based polymorphism on nest defence behaviour in the common buzzard. Among males, light morphs were found to be significantly more aggressive to a perceived threat of nest predation than either intermediate or darkly coloured birds, while there was a non-significant tendency for the reverse among females. The level of aggression observed for each member of a pair was independent of the level of aggression shown by the other member. These results illustrate that polymorphisms can be associated with alternative reproductive tactics in birds, and suggest a possible link between the biochemistry of melanin production and individual behaviour. For most species living in seasonal environments, timing is an important determinant of the success of a breeding attempt. Individuals also face a trade off between current and future reproduction. Here we investigated whether colour morphs differed in their timing of breeding. Light-light and dark-dark pairs were found to breed earlier than the population mean, with light-dark pairs fledging chicks slightly later. Differences in reproductive strategies between morphs may account for the observed differences.

There are several plausible explanations for the initial evolution of aposematism and warning signals but, since these all have support in the form of experimental evidence, it is unlikely that there is one single, simple evolutionary pathway. I investigated the influence of predator psychology on the design of aposematic signals and concentrated on the effects of (innate) colour preferences, learning and memory, using two species of avian predators: ('naYve') domestic chicks (Gallus domesticus) and wild (and therefore experienced) great tits (Paros major). I found that young chicks had innate preferences for some specific colours that were. more saturated and from the long-wavelength part of the spectrum. Furthermore, these preferences were not based on an effect of contrast with the viewing background. However, I did not observe any colour preferences in the great tits, perhaps because they are naturally a generalist species. Domestic chicks trained with two rewarded colours generalise between them to strongly prefer an intermediate colour. I used this phenomenon to further investigate the learning and memorability of colours in chicks. I found an interesting effect, where there is a delay between an encounter with novel prey and when this experience affects behaviour, which could potentially affect avoidance learning. I additionally investigated the relationship between attractiveness and memorability of coloured signals and found that these are potentially distinct features of warning patterns. Finally, observed how great tits learnt and remembered some typically-aposematic colours and compared this to my findings from the chicks. The great tits not only failed to show any colour preferences, but red, yellow and neutral grey stimuli were also equally well learnt in a discrimination task and remembered. The great tits did not show the same generalisation to an intermediate colour as the chicks, but generalised their learning to the novel colour more strongly when the trained colours were unpalatable than when they were palatable

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I conducted a series of studies which looked at influences on avian clutch size. Firstly I examined the traditional view that the demands of rearing chicks create a bottleneck at which clutch size is shaped by natural selection. I considered whether instead other stages such as incubation might also be important. I proposed that reproductive demands at each stage of the breeding season may be interdependent, and by developing a mathematical model, I formalised the argument and showed that data on the relationship between the number of offspring and the expenditure of resources at many stages of the season could reveal the importance of natural selection on clutch size at each stage. I then reviewed the literature on the importance of incubation for clutch size determination. Results indicated that metabolic demands of incubation were appreciable and that the incubation of enlarged clutches imposed penalties on the adults. In a field study of kittiwakes I found that breeding success was depressed during incubation and chick rearing by enlargement of clutches and broods respectively. I measured metabolic rates of kittiwakes during incubation and found them to be comparable with those during chick-rearing. Secondly, I examined whether individual adults within populations differed in their reproductive capacities (i.e. whether there was a range of 'adult quality') and whether this could then affect clutch size. In a study of kittiwakes I found clusters of birds with similar breeding performance, but found that these clusters did not persist between years. In a study of swifts, I found that some individuals were consistently good breeders but that this had negligible effects on the distribution of lifetime reproductive success between individuals. I then examined whether the low clutch sizes and high survival of swifts might reflect a bet-hedging strategy in a fluctuating environment, but found little evidence of this. I looked at whether differences in the amount of space available at the nest site could account for differences in clutch sizes of kittiwakes, but could find no such evidence. Lastly I developed a theoretical model to look at how clutch size might be affected by changes in reproductive effort with age. I examined whether the predictions of optimality models were borne out by the more appropriate population genetics approach and found that in birds the optimality models are robust.

Brian Chen. / Also issued as Thesis (M. S.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1996. / Includes bibliographical references (p. 103). / Supported in part by the Dept. of the Navy, Office of the Chief Naval Research. N0014-93-1-0686 Supported in part by the Advanced Research Projects Agency's RASSP program. N00014-95-1-0834 Supported in part by a National Defence Science and Engineering Graduate Fellowship.

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Given the increasing rate of environmental change that free-living animals are exposed to, there is a growing need to understand the causes and consequences of environmentally-induced phenotypic change and to what extent this phenotypic plasticity is adaptive. As well as being of fundamental biological significance, this knowledge is necessary for the development of effective conservation policies. This thesis examines variation in behavioural, morphological and physiological responses to repeated exposure to environmental stressors. In particular, I focus on early-life effects and discuss the potential consequences of developmental plasticity for later-life performance. Although negative effects of human disturbance on wild animals have been widely reported, few studies have considered the potential for effects on animals occupying burrows or cavities. Procellariiform seabirds are among the most globally-threatened avian taxa and include many species that nest underground. Human disturbance is one of the main threats they face, yet breeding colonies attract increasing numbers of tourists. The European storm petrel Hydrobates pelagicus is a small seabird, belonging to the Procellariiformes, that nests in cavities and is strictly nocturnally active at the breeding colony. The UK’s largest storm petrel colony at Mousa, Shetland, offers a novel system for investigating the potential impacts of human recreational disturbance on a cavity-dwelling animal and the capacity for environmentally-induced developmental plasticity within the remarkably slow development strategy displayed by nestlings. I show that, despite remaining out of sight, human disturbance above ground can have profound effects on cavity-dwelling animals. Nestling survival was significantly lower in areas exposed to high levels of human recreational activity, compared with those reared in areas subject to very low levels of visitor activity (Chapter 1). Furthermore, disturbed nestlings that survived to fledging displayed depressed growth rates (Chapter 2). Plasticity in developmental pathways, however, enabled nestlings to mitigate for poor growth conditions by prioritising energy allocation to structural components and extending the growth period. While such growth plasticity can be adaptive and avoid short-term costs, there may also be long-term costs associated with this strategy. Repeated exposure to stressors can give rise to chronic stress and measures of baseline glucocorticoids are widely considered to be useful for detecting stress in natural populations. Nestlings displayed no evidence for chronic stress, as measured by baseline corticosterone (the main glucocorticoid in birds), in response to repeated exposure to human recreational disturbance (Chapter 2) or investigator handling (Chapter 3). Furthermore, baseline corticosterone did not reflect the differences observed in growth trajectories between the two disturbance categories. Although it is unknown whether the induced changes in growth trajectories of high-disturbance nestlings carry costs, the lack of any effects on corticosterone levels suggests that glucocorticoids are not always an informative measure of individual state. Additional behavioural and physiological data are required to develop an integrated understanding of phenotypic responses to environmental cues. Besides immediate effects on growth and survival, it is well known that conditions experienced during early life can have profound influences on later-life performance. Telomere dynamics potentially provide a mechanistic link between the early environment and fitness outcomes. I show that environmental conditions during growth strongly influence early-life telomere dynamics of entire cohorts, and early-life telomere length is a good predictor of imminent mortality (Chapter 4). Natural variation in the natal environment can lead to marked differences in life-history traits between cohorts and telomere dynamics may be one of the mechanisms underlying cohort effects observed in nature. Unfavourable natal conditions were also associated with the occurrence of hypothermic responses in nestlings (Chapter 5). Such thermoregulatory responses may be adaptive, by facilitating survival during periods of food shortage or cold, but nonetheless could carry costs for growth and long-term fitness. An enhanced knowledge of the causes and consequences of facultative hypothermic responses can advance our understanding of the effects of environmental change. Understanding and predicting how populations will respond to environmental change, however, requires accurate estimation of population size. The ecology of Procellariiformes presents a major challenge to achieving this. Using spatially-explicit capture-recapture data from three closely-related species of storm petrel, it was shown that capture probability varies across spatial and temporal scales (Chapter 6). This quantified variation was used to inform optimal sampling strategies. The results demonstrate that spatially-explicit capture-recapture models can be effectively used to monitor vulnerable burrowing seabird populations, but require a species-specific approach. This thesis addresses key questions concerning the capacity for adaptation and response to environmental stress exposure and the mechanisms underlying individual variation in responses. I demonstrate that multidisciplinary studies of behaviour, morphology and physiology are required to develop an integrated understanding of responses to environmental stressors.

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Perceived conflicts between piscivorous birds and commercial freshwater fisheries are common, and such a perception exists at Loch Leven, a wetland of international importance for nature conservation and a famous commercial brown trout Salmo trutta fishery, where Great Cormorants Phalacrocorax carbo have been shot in large numbers. This thesis describes the foraging behaviour of cormorants wintering on Loch Leven. It summarises changes in wintering numbers over a 32 year period, and reviews data on fish populations, fish stocking rates, angling catches and angling effort in order to seek evidence of detrimental impacts of cormorants on the fishery, and beneficial effects of large-scale cormorant shooting. Finally, this thesis considers turnover within the wintering cormorant population, and its implications for cormorant control. Cormorants spent most of the time roosting, and a single peak of feeding activity occurred early in the morning. Compared to early or late winter, cormorants showed higher foraging activity during mid-winter. Both solitary feeding and flock feeding were recorded, with flock feeding predominating. Solitary feeding was distributed over a wide area. The intensity of flock feeding was less evenly distributed, with 36% of grid squares not used. Overall, 78% of flock feeding activity took place in 23% of grid squares and 59% took place in 13% of grid squares. The best predictor of both solitary feeding and flock feeding intensity of use was mean water depth. Mean water depth was also the best predictor of winter brown trout distribution, although winter brown trout distribution was not a predictor of either solitary feeding or flock feeding intensity of use.