title: Nest sanitation elicits egg discrimination in cuckoo hosts.
abstract: Nest sanitation is a nearly universal behavior in birds, while egg discrimination is a more specific adaptation that has evolved to counter brood parasitism. These two behaviors are closely related with nest sanitation being the ancestral behavior, and it has been hypothesized to constitute a preadaptation for egg discrimination. However, previous studies found little evidence to support this hypothesis. Here, we conducted an empirical test of the association between nest sanitation and egg discrimination in the barn swallow (Hirundo rustica) by inserting a single non-mimetic model egg or a non-mimetic model egg plus half a peanut shell into host nests. Compared to the rejection rate of single model eggs, barn swallows significantly increased egg rejection frequency if a half peanut shell was simultaneously introduced. Our result for the first time shows the impact of nest sanitation on egg discrimination and demonstrates that nest sanitation can elicit egg discrimination in hosts of brood parasites. This study provided evidence for nest sanitation being a preadaptation to egg discrimination by facilitating egg rejection, thereby significantly advancing our understanding of avian cognition of foreign objects. Furthermore, we suggest that egg discrimination behavior in many accepters and intermediate rejecters may be lost or diluted. Such egg discrimination can be elicited and restored after nest sanitation, implying a sensitive and rapid phenotypic response to increased risk of parasitism. Our study offers a novel perspective for investigating the role of so-called intermediate rejecter individuals or species in the long-term coevolutionary cycle between brood parasites and their hosts.
authors.affiliation: Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou 571158, China.
authors.forename: Canchao
authors.initials: C
authors.lastname: Yang
authors.affiliation: Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou 571158, China.
authors.forename: Min
authors.initials: M
authors.lastname: Chen
authors.affiliation: College of Life Sciences, Wuhan University, Wuhan 430072, China.
authors.forename: Longwu
authors.initials: L
authors.lastname: Wang
authors.affiliation: Ministry of Education Key Laboratory for Tropical Plant and Animal Ecology, College of Life Sciences, Hainan Normal University, Haikou 571158, China. liangwei@hainnu.edu.cn.
authors.forename: Wei
authors.initials: W
authors.lastname: Liang
authors.affiliation: Laboratoire d'Ecologie, Systématique et Evolution, CNRS UMR 8079, Université Paris-Sud, Bâtiment 362, 91405, Orsay Cedex, France.
authors.forename: Anders Pape
authors.initials: AP
authors.lastname: Møller
mesh_terms: D000818:Animals; D004192:Discrimination, Psychological; D006790:Host-Parasite Interactions; D009425:Nesting Behavior; D010063:Ovum; D046109:Passeriformes / Q000502:physiology*
keywords: Egg rejection; Evolutionary lag; Hirundo rustica; Intermediate rejecter; Nest cleaning