BREEDING BIOLOGY OF THE GREY-FACED BUZZARD (BUTASTUR INDICUS) IN NORTHEASTERN CHINA

We studied the breeding biology of the Grey-faced Buzzard (Butastur indicus) in Zuojia Nature Reserve, Jinlin province, China from 1996-98. Grey-faced Buzzards are summer residents in northeastern China. Nesting sites were Occupied in March and annual reoccupancy was 60%. Grey-faced Buzzards built new or repaired old nests in late March and laid eggs in early April. Laying peaked in late April and spanned 32 d (N = 15 clutches). Clutches consisted of 3-4 eggs, incubated for 33 +/- 1 d predominantly by the female, to whom the male brought prey. After young hatched, the female also began burning. The mean brood-rearing period was 38 +/- 2 d and nestling females attained larger asymptotic mass than males, but the latter grew faster. Males fledged at a mean age of 35 d and females at 39 d. Young were slightly heavier than adults at fledging, but the wing chord and tail lengths were shorter than those of adults. A total of 50 eggs was laid in 15 nests ((x) over bar clutch size = 3.3), of which 80% hatched and 90% of the nestlings fledged. A mean of 2.4 young fledged per breeding attempt. Overall nest success was 80%. Causes of nest failure were addled eggs and predation on eggs or nestlings by small mammals (e.g., Siberian weasel [Mustela siberica]).