TL;DR: Babblers form the dominant family of insectivorous passerine birds in Malaysian lowland dipterocarp forests, often with large number of species co-occurring together (Lambert & Collar, 2002) as discussed by the authors.
Abstract: Babblers form the dominant family of insectivorous passerine birds in Malaysian lowland dipterocarp forests, often with large number of species co-occurring together (Lambert & Collar, 2002). As many as 22 species of babblers are known to occur in lowland forest in the Panti Forest Reserve in Southern Peninsular Malaysia alone (Yong, 2006). Furthermore, babblers also dominate in terms of overall abundance (Wong, 1986). For instance, Wong (1986) noted that babblers can constitute as much as up to half the individuals and 25% of banded species in mature tropical forests. In spite of their richness and abundance in the forests of Southeast Asia, babbler community ecology is relatively poorly known, with most studies in the region tending to focus on overall bird faunas or the large charismatic species (e.g., hornbills, woodpeckers). Gibson-Hill (1950) listed 13 species of babblers for Singapore, of which six were no longer present at the time of review and most probably extinct then (Chasen, 1923; Castelletta et al., 2000). Another species, the moustached babbler (Malacopteron magnirostre) was treated as a doubtfully occurring species by Gibson-Hill (1950), but subsequently confirmed to occur in Singapore (Lim & Gardner, 1997; Wang & Hails, 2007; Wells, 2007).
TL;DR: Distributional data support the contention that the Trichastoma group originated in the Malayan region and colonized westward through southern Asia and Arabia to Africa (probably in early Quaternary) when humid and warm conditions fostered a continuous Afro-Asian corridor of tropical wooded habitats.
Abstract: By means of a comparative analysis of 12 morphological and behavioural characters, the timaliine genus Trichastoma and its relatives in the tribe Pellorneini are revised to reflect new understanding of inter- and intrageneric relationships (cf Mann et al 1978) Trichastoma as constituted by Deignan (1964) is here subdivided into three unambiguously monophyletic genera, the Malayan Trichastoma and Malacocincla, and the African Illadopsis
Evidence is presented indicating that the reconstituted Trichastoma should be considered the stem genus for the tribe Reviewing the distribution of morphological and behavioural characters, the general implication is that the African forms share a recent common ancestor with those from Asia Distributional data support the contention that the group originated in the Malayan region and colonized westward through southern Asia and Arabia to Africa (probably in early Quaternary) when humid and warm conditions fostered a continuous Afro-Asian corridor of tropical wooded habitats The postulated greater age of the pellorneine assemblage in Malaysia, along with the region's insular geography, has fostered a larger species radiation than that in continental Africa Recent desiccation of Arabia and central and northwestern India probably caused widespread regional extinction of linking forms and has isolated the Pellorneini into two humid forest refuges in equatorial Africa and eastern Asia