Home-range positions in a bird community from south-eastern Australia - questions and answers

Territoriality in birds has been studied for almost 100 years, but a quantitative, simple and common unit which describes the position of a home range or territory on a study site, is lacking. Consequently it is difficult to assess, or to compare, any data that include for example, the putative movement of home-ranges between breeding seasons. The aim of this study of 11 species (18 species breed regularly on the study site) was to determine, using home-range centroids as the position of the home-range (a) the distance between the home-ranges of the male and female of a breeding pair, (b) the scatter of the home-range positions of a repeat (in different seasons) breeding male, and (c) the distance between the nest of a pair and the home-range centroid of the male. Over eight breeding seasons, all nests were found, and sightings of multiple individuals from each species were recorded and used to determine the centroid of the home-range of each individual. Nest positions and homerange centroids were used to investigate the three aims stated above. There are no differences between species for any of the three measurements. The male and female of a pair occupy homeranges with similar positions. Repeat nesters return to similarly positioned home-ranges each season, and nests are not positioned in any particular relation to the centroid of a home-range. Other studies using centroids are rare, but we found some similarities between our data and those from one other study that used the centroid concept.