Reproductive ecology of Brown-cheeked Laughing Thrushes (Garrulax henrici) in Tibet

ABSTRACT.   Most species in the genus Garrulax are found in subtropical or tropical areas of southeastern Asia, with few species adapted to temperate or high-altitude climates. We examined the behavior and reproductive ecology of Brown-cheeked Laughing Thrushes ( G. henrici ) from 1999 to 2005 at Xiongse Valley, Tibet. Cup-shaped nests located 0.4–2.6 m above ground were found in 13 different species of plants, with roses and barberries the most common nest substrates. Laughing thrushes were socially monogamous and no territorial behaviors were observed. Egg-laying was initiated in early May and ended by late August, with clutch sizes of either 2 or 3 eggs     . Incubation started with the first egg being laid and the incubation period lasted 13–17 d     . Young fledged at 14–16 d posthatching     . Of 38 nesting attempts with known fates, at least one nestling hatched in 32 nests (84%) and at least one young fledged from 21 nests (55%). The mean number of fledglings per successful nest was 2.2 (range 1–3; N = 21 nests). Compared to lowland congeners, Brown-cheeked Laughing Thrushes produced smaller clutches and larger eggs. Such differences suggest that laughing thrushes may invest more energy in fewer offspring at higher altitudes, as reported for other avian species and populations, and this may represent an adaptive response to high-altitude environments where climates are harsh and food availability may be limiting.