Niche shift in three foraging insectivorous birds in lowland Malaysian forest patches

Species diversity and feeding guilds of birds in Malaysian agarwood plantations

In Malaysia, the current status of birds inhabiting agarwood Aquilaria malaccensis plantations has not been specifically studied, and little research has been conducted to investigate birds in other agricultural areas (e.g., rubber, acacia, and oil palm plantations) and disturbed areas.  This study was conducted to assess bird species richness and relative abundance, as well as feeding guilds, in two agarwood plantation sites: Universiti Pendidikan Sultan Idris in Tanjong Malim (UPSI), and Slim River (SR).  The presence of birds was recorded using a combination of techniques (mist-nets and point count), while various sources were used to compile feeding information.  This study recorded 364 birds from 36 species in 24 families.  Shannon diversity index (H’) values for the UPSI and SR sites were 2.896 and 2.492 respectively, indicating high bird diversity.  The Bray-Curtis index was 0.29, indicating these sites share few species.  Insectivorous and omnivorous birds were dominant in UPSI (31%), and omnivores at SR (32%).  The commonest insect order at both sites was Orthoptera (UPSI 48%, SR 25%).  While agarwood plantations are relatively homogeneous, they provide a variety of food sources and shelter for a wide range of birds. 

Shifts in foraging behaviour of heterospecific flocking birds in a lowland Malaysian rainforest

Mixed-species flocks (MSFs) serve important roles in bird communities, especially in tropical forests. Although structure of mixed-species bird flocks and its benefits has been intensively studied globally, the foraging plasticity of a species when joining MSFs has rarely been evaluated. The present study examines foraging strategies of the Rufous-crowned Babbler (Malacopteron magnum), Chestnut-winged Babbler (Cyanoderma erythropterum) and Black-naped Monarch (Hypothymis azurea) when participating in MSFs in the Krau Wildlife Reserve, central Peninsular Malaysia. These species exhibit active foraging shifts in utilisation of vertical strata, foraging substrate, attack manoeuvres and foliage density, when foraging in MSFs, compared to when foraging outside MSFs. While the Rufous-crowned Babbler and Chestnut-winged Babbler commonly used gleaning and stretching (to completely extend the legs or neck to reach the food items) manoeuvres when foraging outside MSFs, respectively, they adopted probing manoeuvre and frequently used higher strata upon joining MSFs. The Chestnut-winged Babbler tended to forage on the underside of leaves and the Black-naped Monarch frequently utilised branches when joining MSFs, while they exclusively used aerial leaf litter and live green leaves, respectively, when foraging with conspecifics. The monarch also adopted the hovering manoeuvre and frequently foraged within denser foliage cover when joining MSFs. This study demonstrated that flock members exhibits foraging plasticity either through an expansion or active shift in foraging niches when participating in MSFs, thus suggesting the occurrence of possible foraging improvement and/or reductions in predation risk.