Habitat features affecting bird spatial distribution in the Monte Desert, Argentina

Abstract

The association of .several habitat features with bird guild abundance and bird species diversity was studied, aiming at identifyng proximate factors of bird habitat selection. lit the breeding season, tree-guilds (herbivores and insectivores) always tracked the first axis of environmental complexity, generated by the cover of those trees and shrubs that would supply them with food and foraging surfaces The distribution of long-flight insect-hunters over the same axis was bi-modal due to the different hunting modes of their constituent species. Terrestrial-granivores did not follow any environmental gradient, including the ones generated by the cover of those plant species which supply them with Needs and buds. This result was affected by the sampling design used, but it would mainly arise from the instability with which this guild occupied undisturbed sites. The winter bird assemblage (mainly made up of granivores) did not track any environmental gradient either. During the breeding season, there was a positive and .significant correlation between bird species diversity and habitat vertical, horizontal alai floristic complexity. In winter, no significant correlation was found between these variables. The correlational model based on bird diversity was less efficient to detect proximate factors of habitat selection than the bird guild approach because habitat complexity indices co-varied and the biological meaning of the correlation between bird diversity and habitat complexity was misleading.