Breeding biology of two populations of Chinese penduline tits

The phenotypes and breeding behavior in one species may be different between populations. The local environments, social interactions can all lead to some variations in life history. The thorough investigations of breeding biology over populations can provide insights for us to understand the evolution and diversifications of breeding systems and phenotypic traits from multiple perspectives other than drawing monotonous associations between a factor and a trait. In this study, we explored two Chinese penduline populations, Liaohekou (LHK) and Xianghai (XH), both in the northeast of China located 550 km away from each other. A comparative study of the breeding biology was carried on in the two populations. We found that the climate has no obvious difference in these two populations but has different habitats. Nest emergence and egg-laying were earlier in the more northern population XH. Males in XH has a lower chance of pairing up with a female and exhibit mainly biparental care pattern instead uniparental care that we reported in LHK. The chick fledgling success in the biparental care nests was higher than in the uniparental care nests in XH, but no difference to the uniparental care nests in LHK. Besides, the penduline tits in the two populations were also significantly different in their wing length, tail length and beak shape. These incongruences suggested different food availability, adult sex ratio and migration distances of the two populations. Future studies should experimentally investigate the joint influences of breeding perspectives on the evolution of parental care and mating system.