Reproductive ecology of two sympatric Tibetan snowfinch species at the edge of their altitudinal range: Response to more stressful environments

Knowledge of altitudinal covariation in interspecific competition and life history of birds inhabiting meadow-wastelands in the Tibetan plateau can contribute to our understanding for ecological adaptation of organisms to extreme environments and aid conservation for the unique ecosystem in the world. We reported reproductive ecology of two sympatric Montifringilla snowfinch species (Montifringilla taczanowskii and Montifringilla ruficollis) in a higher altitude wasteland, and compared the data with those of their lower altitude conspecifics. Both species nested in pika burrows and had similar breeding phenology. Nesting habitats of the two species tended to be separated in space as a result of asymmetrical competition, with large-sized M. taczanowskii occupying patches with better vegetation and small-sized M. ruficollis using poorly vegetated patches. In the less harsh lower altitude, however, their nest sites are randomly distributed. Relative to their lower altitude conspecifics, the higher altitude snowfinches had small body sizes but long wings, assuming an adaptation to increasing power demands for flying in thin air. There was a reduced fecundity with increasing altitudes, suggesting an adaptive response to the unpredictable conditions. We argue that the simplified bird community in stressful environments will be more vulnerable to perturbations. This highlights the importance to maintain ecological processes of the ecosystem.