Comparison of habitat at places used by birds with that at places that are representative of the study area or known to be unused

This approach is useful when it is not feasible to map and measure habitats over large areas. Instead habitat is recorded at a sample of small sites chosen at random or on a regular grid to be representative of a much larger area available to the birds. Habitat is also recorded at places where birds are seen. Data of this type can be analyzed by multiple logistic regression with used or representative places being scored as a binary dependant variable (1 or 0) and the habitat measures as independent variables (Manly et al. 1993). As with the other analyses of selection, it is important to think about the availability of the random or representative places to the birds. For example, in the case of selection of foraging habitat by individually marked breeding birds, it might be appropriate to pair each foraging location with a site selected at random on the circumference of a circle centered on the nest with radius equal to the distance of the foraging site from the nest.

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