Modelling the physiology, behaviour and ecology of dive foraging seabirds : determining the availability of prey and predicting the pelagic distribution of the common guillemot Uria aalge in Moray Firth
A mathematical but mechanistic model is presented that is based upon the simplified physiology and feeding ecology of an individual dive foraging animal. In previous theoretical studies of dive foraging behaviour, models assumed dive foraging animals dive optimally based on oxygen as the sole state variable, thus ignoring other likely important physiological factors that are related to the instantaneous energetic requirements of the diving animal. The physiological mechanistic dive foraging model presented includes the additional state variables, namely food (in the gut) and the body mass of the diving animal, for which the oxygen is ultimately required to burn for energy. The physiological model was parameterised for the Common Guillemot Uria aalge, although it may also be applied to other dive foraging animals. Various output parameters are possible from the model, and these were generated from computer simulations to investigate the merits of optimal diving behaviour. The physiological dive foraging model was also used to estimate possible feeding rates of Guillemots from fisheries data made available, which were recorded during winter 1997, in the Moray Firth. These were then used in further computer simulations of the dive foraging model and the various possible output parameters obtained from the model were subsequently used as habitat suitability indices in a novel application of the Ideal Free Distribution, to generate predicted maps of Guillemot distribution, which were tested against the actual concurrently recorded distribution of Guillemots in the Moray Firth. The potential value of the physiological dive foraging model, its limitations and where it, or how its predictions, may further improve, are also discussed. It is hoped that the model will eventually provide an invaluable tool for industrial fisheries, and even wider marine ecosystem management.