© Marcel Burkhardt
Nicholls, D.G., C.J.R. Robertson & B. Naef-Daenzer (2005)
Evaluating distribution modelling using kernel functions for northern royal albatrosses (Diomedea sanfordi) at sea off South America.
Notornis 52: 223–235
Satellite telemetry can provide unique information on the biology and behaviour of mobile animals such as albatrosses. Determining areas of concentrated activity, essential resources and time-related changes in range use is of great importance for theoretical biology, practical conservation, and fisheries management. Utilisation Distributions (UDs), from a probabilistic model of the relative time spent by an animal in an area, were prepared using a kernel function in a Geographical Information System. Properties of the model were investigated, using satellite-tracking data from six northern royal albatrosses (Diomedea sanfordi) during eight over-wintering visits to seas off South America. We analysed UD areas and shape for different settings of the kernel smoothing parameter, a variety of location subsets associated with different sample sizes, sampling time periods and telemetry regimes. Small samples and intermittent transmission regimes reduced the UD range area. Individual bird data sets were combined to give comparable UDs. The UD model may help comparison of range areas and the identification of resource use, but they cannot identify an activity without additional information. For pelagic seabirds, UD preparation and interpretation require judgement and care.
Keywords: Utilisation distribution; kernel; GIS; home range; satellite telemetry; northern royal albatross; Diomedea