Conservation status and reproductive ecology of giant babax Babax waddelli (Aves, Timaliinae), endemic to the Tibet plateau

Abstract

The Lower Risk/near threatened giant babax Babax waddelli is endemic to southern Tibet. The babaxes, living in groups of 3–8 individuals year-round, favoured edge habitats in forest regions where the group encounter rate during the breeding period was 0.35 groups h⁻¹ and population density 0.04 birds ha⁻¹, and in scrub regions they depended on the patches covered with higher bushes in which the group encounter rate and population density were 0.32 groups h⁻¹ and 0.03 birds ha⁻¹ respectively. The global population of the babaxes was estimated to be 120,000 birds. Reproductive and behavioural data were collected from scrub environments in a valley. Egg laying occurred between early May and early June, and clutch size ranged from 2 to 4 eggs, 2.9 on average. Incubation and fledging lasted 16–18 days respectively. Nesting success, measured as the proportion of clutches from which at least one young survives to fledging, was 75%. Some of the babax's nests were cooperatively attended by group members and the others only by both parents. The most preferable nesting areas were in dense bushes more than 1.8 m in height (mainly Rosa sericea, Berberis hemleyana, Cotoneaster divaricatus, Sibiraca angustata and Salix sclerophylla). Such strong dependence on high bushes leaves babaxes more susceptible to vegetation degradation. As a result, the increasing clearance of scrub habitats for firewood is a major current threat to the birds around the mid-Yalong Zangbo River, a region with the densest human population and most rapidly developing economy in Tibet. Their naturally low population density and strongly social grouping behaviour present extra risk factors that have to be taken into account. The importance of vegetation protection for long-term survival of this endemic species is highlighted.