How To Respond Different Nest Predators: A Study In Parus Varius Breeding Season

Nest predation is important for birds natural selection,which produces strong selection pressures in species coexistence,habitat selection and life history strategies.Nest predation has a significant effect on bird population characteristics as one of the important factors influencing the success rate of bird breeding.Therefore,birds have evolved many anti-predation strategies to cope with nest predation pressures under the pressure of natural selection,such as adjusting the number of eggs,changing reproductive behavior,nesting selection and breeding time allocation.Parents have a positive and effective anti-predation strategy,while the more vulnerable offspring also evolved some behavior to resist predators.Under this pressure,what ability can the nestlings evolve to avoid nest predation? Whether the nestlings understand the information contained in the alarm call?Should they make the most reasonable behavior to avoid the occurrence of nest predation? Whether the dangerous information be shared among individuals of similar distribution species which have the same nest predators?This experiment was conducted in Xianrendong National Nature Reserve of Liaoning Province,and the varied tits with high utilization rate of artificial nest were selected as research species.This article explored the following four questions for the varied tits nest predation phenomenon:(1)the first behavior of the parent birds when different predators(Tamias sibiricus and Elaphe anmnal)appeared around the nest box;(2)whether the parent birds can give the corresponding alarm signal according to the activity ability of different age chicks;(3)whether the chicks can respond to the parent alarm signal;(4)whether the chicks can identify similarity heterospecifics warnings.Results suggested:(1)when the mouse appeared in the nest,the first reaction of the adult birds include: attack,alert expulsion,beating with whispering,fly away.The first reaction between the 6-8 days stage(n=40)and the 15-17 days stage(n=31)did not differ significantly(p=0.623).When the snake appeared in the nest,the first reaction of the adult birds include: alarm call,alert expulsion,beating with whispering,fly away.The first reaction between the 6-8 days stage(n=40)and the 15-17 days stage(n=31)differ significantly(p=0.001).(2)When the mouse appeared in the nest,the parent performed ?gagaga? alarm call,and the different parameters of this kind of alarm call had great difference between the 6-8 days and 15-17 days stages.There was a significant difference in the total duration of song output per minute(p=0.022),while the number of song output per minute(p=0.126)and the total number of output syllables per minute(p=0.085)was not significantly different.There was no significant difference in the maximum frequency(p=0.095)while the significant difference was appeared between the minimum frequency(p=0.012)and the mean frequency(p=0.040)in the song parameters.When the snake appeared in the nest,the parent performed ?gegege? alarm call,and the different parameters of this kind of alarm call had great difference between the 6-8 days and 15-17 days stages.There was a significant difference in the total duration of song output per minute(p=0.020),the number of song output per minute(p=0.004)and the total number of output syllables per minute(p=0.037).There was a significant difference in the maximum frequency(p=0.005),the minimum frequency(p=0.027)and the mean frequency(p=0.003)in the song parameters.(3)6–8 days old offspring could not give any response behavior,while 15-17 days old offspring could response with different types of behavior when heard the different kind of alarm call: nestlings crouched down inside the nest cavity in response to ?gagaga? alarm calls given for a mouse(p<0.001),while 87.1% of the nestlings fled the cavity in response to ?gegege? alarm calls given for a snake(p<0.001).Only 12.9% of the nestlings did perform a wrong response.(4)The varied tits and the great tits have the same distribution whose niche has a certain overlap.The alarm call similarity between the varied tits and the great tits for the snake was 0.828±0.025,0.046±0.001 for the mouse.The alarm call similarity between the varied tits for snake and the great tits for mouse was 0.515±0.040.Heterospecifics playback experiment suggested the 32.26%(10/31)nestlings had an wrong response for the mouse alarm call,and only 9.67%(3/31)nestlings had wrong response behavior for the snake alarm call.In summary,the varied tits can adjust its anti-predation behavior according to the type of predator and its degree of risk.Secondly,there is an effective mode of exchange of information between the adults and offspring to reduce the nest predation rate.Thirdly,the adults can adjust their anti-predation behavior based on the activities of the chicks and reproductive trade-offs.Finally,the nestlings can identify the sound structure which was similar to the interspecific song.