Studies On Territory Defence Strategy During Different Breeding Stages In Great Tit(Parus Major)

Territory defence in birds is an important field to study in avian ecology because it can directly affects the reproductive success of birds.According to the fitness theory,territorial birds should adopt different territory defence strategies to improve their fitness and reproductive success.However,there are few former studies on the territory defence intensity changes in different breeding stages.Furthermore,most studies focus on vocal defence,only few studies focus on spatial defence and the dear enemy effect.From March to July of 2016 and 2017,we researched territory defence strategy(territory defence intensity and the dear enemy)in the great tit(Parus major)which bred in artificial nest-boxes at Zuojia Nature Reserve of Jilin Province.We conducted a playback experiment to simulate territory intrusion,we investigated the effects of breeding stages and body condition on territory defence intensity and simultaneously,we investigated the effects of breeding stages on the dear enemy.We suggest that great tit always use spatial defence and vocal defence during different breeding stages,i.e.,spawning period,incubation period,nestling period.Moreover,the intensity of spatial defence and vocal defence didn't significantly change during the three breeding stages.We suggest that great tit adjusted the dear enemy effect in different breeding stages.In spawning period and incubation period,subjects responded more aggressive spatial defence to strangers than neighbors(LLM,z=5.344,P<0.001)(LLM,z=4.197,P<0.001).There was no significant difference in vocal defence intensity between the two playback treatments.The great tit showed the dear enemy,however,in nestling period,there were no significant differences in vocal defence intensity and in spatial defence intensity between two treatments,the great tit didn't show the dear enemy effect.We suggest that body condition didn't significant correlation with spatial defense intensity and vocal defense intensity.In other words,the body condition probably didn't affect territory defence intensity of the great tit.This study proved that great tit didn't adjust territory defence intensity during different breeding stages,it may be related to the higher cost of the territory intrusion in different breeding stages;In nestling period,the great tit didn't show the dear enemy effect,it may be related to the intensification of resource competition among neighbors at this period;Body condition wasn't significant correlation with territory defence intensity,this is probably because factors such as personality may have a stronger influence on the territory defence intensity.