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The study concluded that bill size was highly adaptive in that it was related to fitness (in the broad sense) or to some correlate of fitness. The results are considered in terms of existing niche theory and especially of "character displacement" and the "variable niche hypothesis".

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No description available.

The mechanism of predator categorization has not been understood well yet. I examined how coloration pattern and predator size influence categorization by a prey under laboratory conditions. I tested the reaction of great tit (Parus major) to the plush dummies of sparrowhawk (Accipiter nisus), coloured as sparrowhawk, pigeon, robin and great tit. The same color variations were made in the sizes of a sparrowhawk and great tit. My results indicate that the coloration plays the main role in the recognition. The size is not important in the dummies coloured as the predator and the conspecific but it plays a role in recognition of other tested dummies (coloured as the pigeon and robin).

No description available.

This study investigates the cues used for predator recognition by wild-living untrained birds great tits (Parus major). The experimental approach is used to test the reaction to the variously modified dummies of sparrowhawk (Accipiter nisus) and pigeon (Columba livia f. domestica) under laboratory conditions. The role of key features (yellow eye, hooked beak and talons), colour and size is tested. The results imply that the presence of raptor-specific features is mostly necessary but not sufficient to recognize predator in the presented dummies. Following research revealed that the part of the variability in response of great tits can be taken on the account of personality.

Explaining variation between individuals is a central concept in ecology. Phenotypic variation is the product of genes, environments and their interactions. In contrast to genotypes which are fixed within individuals, environments vary considerably in time and space and have measurable effects on phenotypic quality between and within individuals. The aim of the current work was to identify environmental sources of life-history variation in a wild population of the great tit. The size of Thiessen polygons formed around c. 8000 nestboxes occupied over a 41 year period was used to estimate breeding density at the level of the individual. Linear mixed modelling showed that birds breeding in large territories laid more eggs and produced heavier fledglings that were more likely to survive to breed, than those in smaller territories. Systematic capping of territory sizes revealed that birds breeding in territories more than 2ha in size were unconstrained by density. This method of measuring individual density identified important relationships between density and life-histories and allowed for the accurate separation of other environmental effects usually confounded by density. For example, the life-histories and breeding density of woodland passerines often both vary with distance from the woodland edge. Using the Thiessen polygons to control for density we were able to independently examine edge effects on life-histories. Results confirmed higher density at edges and independently showed that birds near the woodland edge tended to lay smaller clutches of larger eggs later in the season, than birds away from the edge, probably due differences in habitat quality. A further use of Thiessen polygons was to determine the scale at which to measure oak availability in the vicinity of each occupied nestbox. Birds breeding in oak rich polygons laid larger clutches, earlier in the season and had heavier nestlings than birds in oak poor polygons, independently of density and edge effects. What's more, including oaks in life-history models, reduced or eliminated the effect of the Thiessen polygons, suggesting that density dependent life-histories are to some extent explained by reduced oak availability at high density. Clutch size, fledgling mass and recruitment were also found to correlate with local soil calcium. Analyses performed at several spatial scales found the greatest effect of calcium at scales of c.500m. This figure may indicate the average distance females were travelling to obtain calcium rich food during periods of high demands. That breeding environments strongly affect life-histories has been demonstrated by the above work. However, no correlations were found between natal environment and the subsequent life-histories of recruited individuals, probably due to high mortality in great tits, which favours current condition over any character that conveys benefits later in life. This result shows that long-term effects of rearing environments cannot be assumed as it depends on the life-history conditions under which they are found. The results of this study suggest a pervasive role of fine-scale environment variation in determining the life-histories of individual great tits. Moreover, the study demonstrates the efficacy of GIS to model such variation and applying it to explaining life-history variation in long-term databases.

Part One is an investigation of the dawn chorus in the Great Tit. The major conclusions are as follows: Foraging and singing are partly incompatible because of the temporal and spatial separation of microhabitat conditions required for each activity. The dawn chorus occurs at a time of day when: a) foraging efficiency is limited by low light intensity and possibly by lack of mobility of the prey due to low temperature; b) acoustic communication is more efficient than visual displays because of poor visibility and an enhanced sound transmission; c) the rate of territorial intrusion is at its daily peak. Great Tit's readiness to sing and react agonistically towards a territorial intruder is enhanced by experimentally lowering profitability of feeding, but it does not appear to be affected by time of day. Restricting access to food early in the morning leads to higher body weight in the evenings as an anticipatory compensation. Part Two is a study of sampling strategies based on the statistical decision paradigm known as the Two-Armed Bandit problem. I studied transition behaviour in foraging experiments using concurrent variable ratio schedules. The birds' foraging behaviour approximated the predictions of a dynamic programming algorithm that calculates the optimal balance between exploring and exploiting for finite time horizons. The birds' response to patch diversity and time horizon was closer to molar maximization (total rewards over a certain period) than to molecular maximization (maximising the instantaneous probability of reward). When the environment is not totally stable these two possibilities conflict, and my results supported molar maximization. Part Three investigates the trade-off between maximising foraging efficiency and efficient territorial defence. Great Tits behaved close to the predictions of the Marginal Value model when there were no territorial intrusions, but modified their feeding behaviour in the predicted way when the probability of intrusion was higher.

Changes in climate shape biological populations. They can alter spatial distributions, the timing of life history events, and even the species themselves. We are now experiencing a period of rapid directional climate change, alongside seasonal fluctuations. This thesis investigates temporal changes in life history events, phenology, as a climate response. I explore the causes and population level consequences of change in breeding phenology of two wild bird populations from Wytham Woods, UK. I test how great tits (Parus major) and blue tits (Cyanistes caeruleus) achieve temporal synchrony between the peak demands of their breeding and the peak abundance of their prey species (winter moth caterpillars - Operophtera brumata) in an inter-annually variable environment. I demonstrate great tit (Parus major) incubation behaviour fine-tunes the timing of hatching in response to ambient temperatures right up until hatching (Chapter two). Temperatures within the nest box, however, appear to play little role in the breeding phenology of blue tits (Cyanistes caeruleus) (Chapter two). I discuss the merits and limitations of statistical approaches for cue identification (Chapter six), finding the method and time period of data used both affect the cue identified and predictive accuracy. The second part of this thesis explores the influence of a directionally changing environment on great tit phenology. I use an integral projection model (IPM) to predict population dynamics over the 21^st century, showing that if the cues used by both interacting species change sufficiently closely, temporal synchrony can be maintained through both phenotypic plasticity and micro-evolution (Chapter 5). However, if the cues diverge mismatch will arise (Chapter 5) causing population declines when certain thresholds are passed (Chapter 4). This work contributes to understanding how phenological synchrony is achieved, how it might change in the future, and its population impacts. In Wytham Woods it appears that great tits have a great deal of flexibility in multiple components of their breeding cycle, allowing them to retain synchrony with their caterpillar prey in a fluctuating environment. These birds are relatively resilient to negative phenological impacts from climate change. Only if the cues used by the predator and prey completely diverge do we predict consistent declines in population size during this century.