| There is an important significance of habitat selection for the survival and development of the whole population,great habitat environment can not only provide sufficient food and suitable breeding sites,but also to avoid predators,natural disasters and bad weather,this is the root of their survival.Different species have differences on required habitats.Nest site selection plays a critical role in the reproductive success of a breeding population.Since 2013,the restoration project of the Chinese Crested Tern(Thalasseus bernsteini)and Great Crested Tern(T.Bergii)had been conducted in Jiushan islands using social attraction technology.In order to understand the mechanism of nest site selection of the mixed breeding colonies and the causes of breeding failures,during 2015 breeding season,we used the same technology attracting the Chinese Crested Tern and Great Crested Tern at Tiedun Dao in Jiushan Islands,and intended to detect the factors influencing their selection orders of the nest sites,and the reproductive success.The main results were as follows:1.In Jiushan archipelago,the nest site selection order of the Chinese Crested Tern is from 4 nesting area,and followed by 6,5,2,8 and etc.(n=36);That of the Great Crested Terns and Chinese Crested Tern is from 4,and then 6,2,8,10 and etc.(n=34).By linear stepwise regression analysis,we found that,vegetation coverage,rock coverage,land coverage,sound source distance,the nests density and human disturbance have significant impacts on the nest site selection order of the Chinese Crested Terns,ground slope,vegetation coverage,land coverage,rock coverage,nest density,simultaneous nest number and human disturbance have significant impacts on the nest site selection order of the Great Crested Terns.2.By curve fitting in regression analysis,we found,the vegetation coverage and human disturbance has a significant negative correlation with the nest site selection order of the Chinese Crested Terns,whereas,the rock coverage,land coverage and sound source distance have positive correlations with it.The results indicate that the Chinese Crested Terns tend to nest primarily at the area with high vegetation coverage,and lower rock and land coverage,and near the sound source,and removed from human disturbance.3.While for the Great Crested Terns,ground slope,vegetation coverage and human disturbance have a significant negative correlation with their nest site selection order,but land and rock coverage,existent nests and simultaneous nests have a significant positive correlation.These results indicate that besides the vegetation coverage,land and rock coverage,other individual's behavior also have an important impact on the nest site selection of the Great Crested Tern.4.The reproductive success rate of the Chinese Crested Tern was 43%at Tiedun Dao.Its influencing factors include vegetation coverage and land coverage.The reproductive success rate of the mixed colony at Tiedun Dao was 40.4%.Its influencing factors include vegetation coverage,land coverage,sound source distance and decoy number.The vegetation coverage has a significant negative correlation with the reproductive success rate of the mixed colony,but land coverage,sound source distance and decoy number have a significant positive correlation.These results indicate that the higher vegetation coverage could decrease the reproductive success,but the higher land coverage,more decoys and far from the sound source could increase the reproductive success.5.The reproductive success of Chinese Crested Terns has no significant correlation with their nest site selection order,but the mixed breeding colony had a higher reproductive success with those later nests.6.Our results suggest that controlling the vegetation,keeping observation blinds at a certain distance from the colony,and leave more open room at the nesting ground for the breeding colony will enhance the success of tern reproduction,and the restoration project as well. |
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