Foraging Patterns Reveal Niche Separation in Tropical Insectivorous Birds

Abstract

The study examines the uses of attack maneuvers and foraging substrates by ten insectivorous passerine birds to explain how these trophically similar species can coexist in the same habitat, a central question in ecology. Information on the foraging height, attack maneuvers, substrate and foliage density was collected independently for each foraging bird. Sallying was the most frequently used attack maneuver, and leaves were the most frequently used substrate. Statistical analyses showed that the variation in the foraging data was significantly influenced by foraging height, followed by attack maneuver, substrate, and lastly foliage density. The foraging height, the parameters of the attack maneuvers and substrate effectively divided the birds into three foraging guilds: (1) ‘High-sally insectivores’ — birds that foraged in higher strata using sallying tactics, namely Arctic Warbler Phylloscopus borealis, Black-naped Monarch Hypothymis azurea, Asian Paradise-flycatcher Terpsiphone paradisi and Asian Brown Flycatcher Muscicapa dauurica; (2) ‘High-foliage insectivores’ —birds that foraged in higher strata using glean-stretch-hang tactics, namely White-bellied Erpornis Erpornis zantholeuca, Green Iora Aegithina viridissima, and Pin-striped Tit-babbler Macronous gularis; and (3) ‘Understory insectivores’ —birds that foraged in lower strata, namely Abbott's Babbler Malacocincla abbotti, Chestnut-winged Babbler Stachyris erythroptera, and Rufescent Prinia Prinia rufescens. Except for Asian Paradiseflycatcher and Asian Brown Flycatcher, no other two species used similar foraging heights, substrates and attack maneuvers at the same time. However, the use of foliage density differed significantly between these two species. Therefore this parameter should also be taken into consideration in analysis of foraging niche in tropical birds.