The Defensive Effect Of Reduced Hole Size On The Predator In Sitta Europaea

Nest predation is one of the main drivers for the failure of avian breeding,and is therefore an important factor affecting avian breeding success rate.Because breeding birds need spend several weeks in fixed locations(laying eggs,hatching and feeding),nest defence is a key factor of breeding success.Eurasian nuthatch,(Sitta europaea)is a secondary cavity nesting species,and specially,they always reduce the size of the entrance hole and seal up cracks with mud.Our aim in this study is to assess whether the reduced hole size makes the nest more secure.From March to July in 2014 and 2015 at Zuojia Nature Reserve of Jilin Province,we conducted dummy experiment to observe the nest defence behaviour of Sitta europaea when their nests exposed to three predator dummies with different size.During the study,we found 37 nuthatch nests in total,the average clutch size is 4.76 + 0.77,breeding success rate is about 36.73%.In this study,first egg date of Sitta europaea lasted from April 14 th to May 3rd.As a whole,the spawning time was mainly in the late April.Dummy experiment showed that Sitta europaea responsed more strongly to small size predator(snake and small squirrel dummy)than to larger ones(larger squirrel dummy).The attack behavior on small predators was significantly different from attack behavior on large predator(Wilcoxon test:Z =-3.617,P = 0.001,Z =-3.587,P = 0.001).Our findings corroborated that the modification of size of the hole in Sitta europaea has a defensive effect on the predator.