Study Of The Influence Of Breeding Synchrony And Nest Density On The Ratio Of Extra-pair Paternity Of Varied Tit(Parus Varius)

Explaining the reasons of extra-pair copulation(EPC)of birds through the genetic is still unclear. Several hypotheses have been proposed already, however, based on the ecology to study the various ecological factors which influence the extra-pair paternity(EPP) level has never been stopped. The application of the molecular biology technology completely changed the public opinions about the avian mating system. In contrast to previous expectations, there is few real monogamy, about 90% of the birds were found existing extra-pair offspring(EPO). Even in social monogamous birds, more than 11% of the offspring are extra-pair offspring. Several studies have discussed the variation of EPP from different views, but for different species, the ratio of EPP is different, even the same species, the ratio of EPP also appears variable. Therefore, the factors affecting the ratio of EPP became the focus of discussion. This study plan to analyze the breeding synchrony and breeding density which affect the ratio of EPP at an ecological view. In order to explain that whether the ratio of variation of Varied Tit(Parus varius) is relate to the some ecological factors. Our study will start from three parts. Firstly, Identified the EPP of Varied Tit. Secondly, breeding synchrony is the impact on the ratio of Varied Tit’s EPP. Third, breeding density is the impact on the ratio of Varied Tit’s EPP. Research methods and results are as follows:(1) There were four pairs of Varied Tit which are breeding and ringing in the breeding season. Then we carried the experiments using the fake bird to invasion in order to observe of its size and territorial behaviors. Results showed that: the radius of breeding area was 35.58±4.56 m.(2) From 2009 to 2014, we obtained 65 nest dates of Varied Tit which were all complete. The paternity test results showed that 34 nests(52.3%) with extra-pair paternity, 21.3% of all the offspring(413) were extra-pair offspring. The ratio of EPP of Varied Tit is on a high level.(3) There are two peaks in a breeding season of the Varied Tit. We would analysis the correlations of those: the ratio of nests which had breeding synchrony and the ration of nests which had EPP,both of them were in a same breeding peak, the ratio of nests which had breeding synchrony and the ratio of extra-pair offspring at the nest with breeding synchrony. The results showed that: the correlation coefficient of the ratio of nests which had breeding synchrony and the ration of nests which had EPP was R=0.36(P=0.25), the correlation was not significant. Also, the correlation coefficient of the ratio of nests which had breeding synchrony and the ratio of extra-pair offspring at the nest with breeding synchrony was R=0.19(P=0.55), the correlation was not significant. All above showed that, there was no correlation between the breeding synchrony with the ratio of EPP.(4) Under the premise of breeding synchrony, we search the number of neighbors which was at a range of 350 meters with the central nests. At the basis of the number of the neighbors, we would divide different breeding density gradient. And then we explored the different breeding density gradient whether influence the ratio of EPP. The results showed that: the correlation of the density gradient and the ratio of nests which had EPP was R = 0.76(P = 0.13), the correlation was not significant; the correlation of the density gradient and the ratio of extra-pair offspring was R = 0.76(P = 0.13), the correlation was not significant, either. the proportion of breeding density gradient and extramarital offspring correlation coefficient R =-0.78(P = 0.12), All above showed that, there was no correlation between the breeding density with the ratio of EPP.