鸟类的清巢行为及其对杜鹃寄主卵识别能力进化的影响

巢寄生是寄生性鸟类把把繁殖代价转嫁给寄主的一种特殊繁殖对策，是研究协同进化的经典系统，也是行为和进化生态学的研究热点之一。鸟类卵辨别行为（包括卵识别和卵拒绝）是一种反寄生行为适应，清巢行为则是鸟类普遍的一种清理巢内异物的行为。以往认为清巢行为是卵辨别行为进化的预适应，但尚缺乏实验证据支持。杜鹃的寄主则同时具备这两种行为，如果清巢行为是卵辨别行为进化的预适应，那么我们预期杜鹃寄主的清巢行为可促进其卵辨别行为的进化。反过来，在鸟类巢寄生系统中，寄主的卵辨别行为可强化其清巢行为。或者，鸟类的清巢行为和卵辨别行为是分别独立进化的，但这需要对更多的寄主鸟种进行系统发育比较。本项目拟在中国的多杜鹃寄生系统中，通过野外实验检验以上假说，比较鸟类清巢行为的种间、地理种群以及鸟类生活史不同阶段的差异，了解其在杜鹃寄主卵辨别行为进化中的角色，填补该领域的研究空缺，深化人们对种间互作关系的认识。

Avian brood parasitism is a breeding strategy in which a parasitic bird manipulates a host to raise its offspring, and it provides tractable systems for studying coevolutionary processes in nature and has been attracting much attention in behavioral and evolutionary ecology. Egg discrimination (i.e., egg recognition and rejection) behavior is a more specific adaptation that counters brood parasitism. Nest sanitation is universal in birds compared with egg discrimination, which only occurs in a more restricted range of bird species, and thus, the hosts of brood parasites possess both kinds of behavior. Therefore, nest sanitation and egg discrimination behavior are ideal for studying avian cognition.. Previous work suggested that nest sanitation is the ancestral behavior and a preadaptation from which egg discrimination subsequently evolved, but to date there has been little evidence for this suggestion.. Combining such flexibility of egg discrimination with the fact that hosts possess both nest sanitation and egg discrimination behavior, we hypothesized that a need to exercise nest sanitation may elicit egg discrimination because nest sanitation will cause hosts to pay more attention to their nest contents as a consequence of an increase in motivation, if the former is the original behavior and a preadaptation to the latter.. we further hypothesized that host species that consistently eject foreign eggs may exhibit highly frequent and consistent nest sanitation behavior as a consequence of having evolved an enhanced cognitive ability, selected for under the pressure of brood parasitism, which has a positive feedback effect on both egg ejection and nest sanitation. In addition, egg discrimination is a flexible behavior that can change among populations of a single species or among different stages of the reproductive cycle in a single population. Social learning and risk of parasitism may account for such changes. . Alternatively, it is also possible that nest sanitation and egg ejection are unrelated and that foreign egg recognition and ejection evolved independently of nest sanitation. Therefore, robust phylogenetic comparisons of multiple species across brood parasite-host systems are needed about the role of nest sanitation in the evolution of foreign egg ejection.. The proposed proposal focuses on nest sanitation in birds and its role in the evolution of egg discrimination in cuckoo hosts in a multiple-cuckoo species parasitism system in China, aims to test the above hypotheses and to facilitate understanding of coevolutionary processes and the ecological consequences of species interactions in nature.