Breeding Ecology Of Two Rosefinch Species In Alpine Shrub Environment Around Mid-Brahmaputra River

We studied the breeding ecology of two species in the genus Carpodacus which had comprovincial distribution in alpine shrub environment of Middle Brahmaputra River near Lhasa, Tibet, during three breeding seasons over 2002-2004. Due to different diet and nest shrub height, Pink-rumped Rosefinch Carpodacus eos and Streaked Rosefinch Carpodacus rubicilloides had different niches although both species overlapped to a great extent. Egg laying occurred from mid-July until mid-September in C. eos, and between early July and mid-August in C. rubicilloides, with a 10-15d delay in the former than the latter. Relative to those (most between April and May) other passerines in the same area, the later onset of reproduction could be associated with food supply.The mean clutch size was 3.77 eggs in C. eos and 3.67 eggs in C. rubicilloides with a same modal clutch size of 4. In C. eos, the mean mass of fresh eggs was 2.15g. Fresh egg mass could be calculated by the formula: W=0.529LB~2. Egg mass loss during incubation period could be expressed by the equation y = 2.172-0.027t. In C. rubicilloides, the mean mass of fresh eggs was 3.61g. The relationship between fresh egg mass and dimensions could be expressed as W=0.512LB~2. Water loss during incubation period could be expressed by the equation y = 3.623-0.042t.For C. eos, egg mass increased with laying order except for the second egg. In C. rubicilloides, on the contrary, mean egg mass decreased with the laying sequence. There was a significantly negative correlation between clutch size and egg laying date in C. eos. Similarly, a negative but non-significant relationship was also detected between clutch size and altitude. Clutch size of C. rubicilloides wasn't correlated either with egg laying date or with elevation.The mean incubation period was 15.0 days in C. eos, similar to 15.3 days in C. rubicilloides. Both species had longer incubation length than other low elevation rosefinches. But within the span of elevation sampled, incubation period of each species had no significant correlation with elevation and egg laying date.The mean nestling period was 13.5 days in C. eos, shorter than 14.0 days in C. rubicilloides, both shorter than those reported in most other rosefinches. The fledglings' weight and growth of external organs didn't reach their adult size of these two species. The provision for postfledging is needed for some time.Males of both species delivered food for females since egg laying initiation until early nestling period and participated in nestling provisioning. During incubation period of C. eos, female spent 54.0% of her time in nest attentiveness, during which her mate provided food for her at a rate of 0.34 trips/hr, and of C. rubicilloides with 67.6% nest attentiveness and 0.59 trips/hr male feeding rate.The diets of nestlings were different in these two species. Nest predation might be primarily responsible for the loss of eggs and nestlings.