The use of logistic regression in modelling the distributions of bird species in Swaziland
The method of logistic regression was used to model the observed geographical distribution patterns of bird species in Swaziland in relation to a set of environmental variables. Reporting rates derived from bird atlas data are used as an index of population densities. This is justified in part by the success of the modelling process. For each species the variables which were significantly related to its distribution were identified. Various methods for coding environmental variables from maps were investigated. A jack-knifing technique was used to demonstrate the predictive power of the logistic models. A criterion for assessing the goodness of fit of the logistic models was derived.