Aspects of flocking behavior in an endemic Pacific island white-eye

Abstract

The Bridled White-eye is a little known species endemic to the Mariana Islands in the tropical Pacific. Based on observations of social behavior and on movements of color-banded individuals, I evaluated which of four flocking strategies the Bridled White-eye appeared to use: (1) group territoriality, (2) permanent membership flocks, (3) site-dependent flocks, and (4) temporary flocks. Banded birds declined in frequency of occurrence from a single banding site and exhibited no clear defense of territorial boundaries. Many banded birds remained in the study area for up to 14.5 mo. Small groups of at least three birds were family groups, although larger groups of ca. 50 birds also foraged together and then dispersed into smaller flocks. Plotted resightings of individual banded birds suggested that home ranges of individuals were overlapping. These observations led to the conclusion that the Bridled White-eye exhibited flocking characteristics intermediate between permanent membership and site-dependent flocks.