Mixed‐species bird flocks in dipterocarp forest of north‐central Burma (Myanmar)

Abstract

We studied the bird community in deciduous, dipterocarp forest of north‐central Burma (Myanmar) during December 1994, March 1996, and January 1997 and 1999. Most members of this community participated in mixed‐species flocks. Seventy‐three flocks were encountered during our study, containing 52 species. Of these, 25 species occurred in more than 10% of flocks, and were included in our analyses. There were 26 significant correlations among species pairs, 25 of which were positive. Cluster analysis indicated that there were three principal types of flocks: one consisting mostly of small passerines and picids, commonly including Common Wood‐Shrike, Small Minivet and White‐browed Fantail, among others; a second type consisting mainly of sylviids, e.g. Arctic, Dusky and Radde's Warblers; and a third type which generally centred around Greater and Lesser Necklaced Laughingthrushes. Bird‐eating hawks were numerous at these sites, and we witnessed several attacks on flocks during the study. Thus we infer that enhanced protection from predation is an important benefit conferred by flock membership. In contrast, there was little overlap in foraging behaviour among species, suggesting that foraging facilitation is a relatively minor benefit enjoyed by flock members, although we did observe White‐browed Fantails and Greater Racket‐tailed Drongos kleptoparasitizing other species on occasion.