Effects Of Habitat Fragmentation On The Use Of Nest Site Resources And Life History Traits Of The Great Tit In Thousand Island Lake

Research purpose:In order to investigate the effects of habitat fragmentation on the use of nest site resources by birds and their life history traits, test some important hypothesis about the response of birds’life history traits to the habitat fragmentation, predict the long term evolutionary trends of birds in fragmented habitats, and provide some theoretical suggestions for birds’and other species’protection in fragmented habitats.Research location:Thousand Island Lake, Zhejiang Province, China.Research methods:We conducted our research on22islands with series ranges of areas and degrees of isolations and5neighboring Mainland sites. We used the line transect method to place the artificial nest boxes to attract the great tit (parus major). Totally, we placed716artificial nest boxes during year2008and2009. These nest boxes are checked at2to4days during the great tit’s breeding season from year2008to2010.Main results:1. Effects of habitat fragmentation on the use of nest boxes by great tit.We analyzed the relationships between island area, island isolation, predator activity, vegetation cover and nest box orientation and the use of nest boxes by great tits. Our results show that great tits preferred nest boxes with lower predator activity, lower vegetation cover, and an eastern or southern orientation. Island area and isolation did not affect the use of nest boxes directly, but island area indirectly influenced the use of nest boxes by affecting predator activity. Our results suggest that more attentions should be paid to environmental variables that directly affect the use of nest site resources by great tits. Our study also highlights the importance of the indirect effects of habitat fragmentation on the use of nest site resources by great tits.2. Effects of habitat fragmentation great tit’s life history traitsBy measuring great tit’s life history traits during its breeding season from year2008to2010, we analyze the changes of great tit’s clutch sizes, egg volumes, breeding cycle, and breeding success between the islands and between the islands and mainland sites. The results of analysis between islands show that,(1) between islands, clutch sizes have a negative relationship with the island area and a positive relationship with the island isolation.(2) Egg volumes have a positive relationship with the island area, while the island isolation has no significant effects on the egg volumes.(3) And the breeding success on the islands has a negative relationship with the predator activity. We also find that island area and isolation did not affect the breeding success directly, but island area indirectly influenced the breeding success boxes by affecting the predator activity.(4) There are no significant differences of the breeding cycle between the islands.The results of analysis between islands and mainland sites show that,(1) clutch sizes have no significant differences between in mainland sites and in middle and large islands, but clutch sizes are smaller in mainland sites than in small islands.(2) Egg volumes have no significant differences between in mainland sites and in small islands, but egg volumes are smaller in mainland sites than in middle and large islands.(3) And the breeding cycle has no significant differences between in mainland sites and in all islands.(4) While the breeding success in mainland sites is lower than in all islands.Therefore, we confer that many of the great tit’s life history traits changed between different islands after about50years from the building of Thousand Island Lake. This also happened between islands and mainland sites. In order to explain the mechanism of these changing more clearly, we suggest that it should be tested for more parameters, such as food resources, parasites abundance, and body size of the breeding great tits, in the future research.