Comparison Of Anti-Predation And Anti-Parasitism Behaviours In Seven Tit Species

Nest predation and brood parasitism are the main causes of bird breeding failure.Selection pressure urges birds to evolve suitable breeding strategies to maximize their fitness.For example,in the face of nest predation,birds will make adjustments in nest site selection,nest defense behavior and reproductive investment.Different environments,different types of predators and different levels of danger,all may lead birds to show different anti-predation behaviors.And in response to nest parasites,host evolved the ability to recognize eggs and chicks.Therefore,nest predation and brood parasitism are the most important selection pressures that affect the reproductive performance of birds.In this study,we compared the anti-predation behaviors of five species of cavity nesting birds in the family Paridae,namely,cinereous tit(Parus cinereus),marsh tit(Poecile palustris),varied tit(Sittiparus varius),willow tit(Parus montanus)and coal tit(Parus ater),and the anti-parasitic behaviors of cinereous tit,marsh tit,varied tit,willow tit,coal tit,greenbacked tit(Parus monticolus)and ground tit(Pseudopodoces humilis),in order to explore the similarities and differences of the reproductive strategies adopted by tit species.The main results are as following:(1)In Saihanba of Hebei,the proportion of tit individuals giving a hissing call and nest predation were similar among three tit species(cinereous,varied,and marsh tits).In Xianrendong of Liaoning,the proportion of cinereous,varied,and marsh tit individuals giving a hissing call differed significantly but nest predation did not.Cinereous and varied tits showed no differences in clutch size,date of the first egg,nest predation and nesting success between individuals that gave and those that did not give a hissing call.These results indicated that for tit species that breed in nest boxes distributed within the same area,there is inter-specific variations in hissing call,but these are not significantly correlated with nest predation risk.(2)When confronted with nest predation risk,the probability of cinereous tits' escape decreased with increasing latitude,that is,the proportion of parent birds that escaped from the nest was significantly higher in southern than in northern populations.For the parent birds that did not leave the nest,the proportion of individuals who produced a hissing call for nest defense was significantly lower in the southern than in the northern populations.In addition,the clutch size in the southern cinereous tit population was significantly smaller than that in the northern population.Our study confirms in a single species that under predation risk,parent birds in the tropics prioritize their own safety over the safety of their future generation,while the birds in the northern hemisphere do the opposite.We suggest that geographical variation in anti-predation behavior of the cinereous tit may be related to the reproductive value of the offspring,such as clutch size.(3)The Hebei population(egg rejection rate: 58.8%,n=17)and Liaoning population(53.3%,n=15)of the cinereous tit,and the Guizhou population(100%,n=12)and Taiwan population(75%,n=12)of the green-backed tit all exhibited high egg recognition ability.The egg recognition ability of these tits was significantly greater than the other five species in the Paridae family.The varied tit(5.4%,n=37),marsh tit(8.3%,n=12),willow tit(Hebei: 26.3%,n=19;Beijing: 9.5%,n=21),coal tit(20%,n=15),and ground tit(0,n=5)had low egg recognition abilities and there were no significant differences between these five species.Therefore,we speculate that tits that are widely distributed in the Indomalayan realm,which overlaps with small cuckoo species in the south,possess egg recognition ability.However,tits that are located in the Palaeartic realm have low or no egg recognition ability.(4)Identifying and rejecting foreign eggs is a huge cognitive challenge for many cuckoo hosts.To understand the effect of cuckoo brood parasitism on the evolution of brain size in cinereous tits,we tested the egg recognition ability of great tits with mimetic white-rumped munia(Lonchura striata)eggs and non-mimetic blue model eggs.The results showed that there was no significant difference in head size and rellative head size between individuals with egg recognition ability and individuals without egg recognition ability.Therefore,we suggest that the cognitive ability of cinereous tits to foreign eggs evolved under the parasitic pressure of cuckoos did not lead to the evolution of its brain size.(5)The cinereous tits showed moderate rejection of white-rumped munia(53.3%)and red-rumped swallow(Cecropis daurica)(50%)eggs.Based on the results of egg color analysis of eggs of cinereous tits,white-rumped munia,red-rumped swallow and blue model eggs,we showed that the egg spots of cinereous tit have the signal function,which may be an important clue for them to recognize and reject foreign eggs.