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.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:461333 |
| Date | January 1979 |
| Creators | Kacelnik, Alejandro |
| Contributors | Krebs, John R. |
| Publisher | University of Oxford |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://ora.ox.ac.uk/objects/uuid:8155d6b1-2df4-4e13-987d-a4d3b1ee3b68 |
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