Habitat categorization, niche overlap measures and clustering techniques

Saino N. & Fasola M.

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We compared the descriptions of niche overlaps in a guild of Laridae and Stemidae, as obtained with different grains of habitat categorization, by different overlap algorithms and by different clustering techniques. All the values of niche overlap were obtained from a unique rnatrix of foraging habitat utilization by the eight species considered. Very dissimilar descriptions of the niche overlaps were given by the overlap algorithms and by the clustering techniques and the strongest discrepancies arose when the values obtained from different levels of grouping of the habitat categories were compared. We conclude that values of niche overlap obtained by different algorithms and levels of resource grouping differ widely. An a priori categorization of the resources should be avoided. Except in cases very generaI patterns of resource use are to be compared. Multivariate techniques may offer an alternative approach in studies OlI resource partitioning among populations in a guild.