Winter Ecology of Three Species of Phylloscopus Warblers

Abstract

This study focused on three species of Phylloscopus warblers, P. humei, P. xanthoschistos, and P. chloronofus which overwinter sympatrically in the foothills of western Himalayas. The patterns of habitat occupancy, foraging behaviour, and foraging microhabitat of three species of warblers were examined to determine the nature of ecological complementarity facilitating their co-existence in the non-breeding season. Moreover, investigating the morphology-ecology associations among congeners also becomes critical since recent divergence may hinder our understanding of the mechanisms of their ecological segregation, as is the case with these species. Hence, morphology-ecology associations were also examined. A total of 91 points were sampled for bird detections five times each between December 2006 and March 2007. Prey abundances across habitat types were quantified. Behavioural data was also collected. The three species were found to differ in the occupancy of the sampled area. However, the bird occupancy did not correlate with differences in prey abundances across habitat types. The warbler species showed clear segregation in the use of foraging behaviour, foraging microhabitat, and proportion of large prey intake. The movement pattern was also found to vary across the three species. Morphology-ecology associations revealed the close interaction of morphology and ecology in shaping the ecological segregation of the three species in the non-breeding season. One major finding was that P. xanthoschistos is able to meet its demand for large arthropods in this northern site (31.5 % large prey intake) previously believed to be low in large arthropod abundance. Finally, the study demonstrated that the ecology of P. xanthoschistos (previously Seicercus) is very similar to other members of the genus Phylloscopus.