Egg rejection and egg recognition mechanism in a Chinese Azure-winged Magpie(Cyanopica cyanus)population

Recognition and rejection of foreign eggs are effective defense of hosts against brood parasitism.However,brood parasitism can impose various selection pressures on different geographic populations of the same host species.In a multiple cuckoo system in China,Azure-winged Magpies(Cyanopica cyanus)are parasitized by both Indian Cuckoos(Cuculus micropterus)and Asian Koels(Eudynamys scolopaceus).In this study,egg recognition ability and recognition mechanism of the Azure-winged Magpie were investigated using a population in Fusong,southeastern Jilin,China.The results showed that 55.6%(20/36)of the Azure-winged Magpies correctly rejected quail(Coturnix japonica)eggs in their nests,while 13.9%(5/36)of the individuals experienced rejection costs by wrongly rejecting their own eggs.Azure-winged Magpies could accurately reject the experimental eggs when the number of such eggs in the nests was the same as that of the magpie eggs.However,Azure-winged Magpies do not recognize and reject conspecific eggs(0/28).The present study indicates that the Azure-winged Magpie has moderate egg recognition ability toward non-mimetic quail eggs and shows a true recognition mechanism with rejecting foreign eggs by accurately recognizing their own eggs.However,they cannot recognize conspecific eggs.

Brood sex ratio in the Yellow-bellied Prinia(Prinia flaviventris)

Background:The adjustment of sex ratios in birds can occur at the egg and nestling stages. Previous studies showed that the sex ratio was affected by environmental factors and parental condition; it may result in seasonal and ecosystem differences.Methods:In this study, the brood sex ratio of the Yellow-bellied Prinia(Prinia flaviventris) in the Nonggang area, Guangxi, southwestern China, was investigated during the breeding season from May to June in 2013 using PCR amplification from whole-genome DNA extracted from blood samples. A total of 31 nests of Yellow-bellied Prinia, including 132 brood fledglings and 31 pairs, were sampled.Results:The results showed that the brood sex ratio of the Yellow-bellied Prinia was 1:1, and sex ratios of different nests were evenly distributed within the study area. No significant relationship was found between parental quality and nest characteristics with the brood sex ratio.Conclusions:The present study indicated that no brood sex ratio bias in the Yellow-bellied Prinia highlighted the complexity of sex ratio adjustment in birds. In spite of our negative results, the lack of an association between brood sex ratio and parental quality and environmental factors in the Yellow-bellied Prinia provides valuable information on the adjustment of sex ratios in birds.

Development and behavior of Plaintive Cuckoo(Cacomantis merulinus) nestlings and their Common Tailorbird(Orthotomus sutorius) hosts

Background:Our knowledge of avian brood parasitism is primarily based on studies of a few selected species.Recently,researchers have targeted a wider range of host–parasite systems,which has allowed further evaluation of hypotheses derived from well-known study systems but also disclosed adaptations that were previously unknown.Here we present developmental and behavioral data on the previously undescribed Plaintive Cuckoo(Cacomantis merulinus) nestling and one of its hosts,the Common Tailorbird(Orthotomus sutorius).Methods:We discovered more than 80 Common Tailorbird nests within an area of 25 km2,and we recorded nestling characteristics,body mass,tarsus length and begging display every 3 days for both species.Results:Plaintive Cuckoo nestlings followed a developmental pathway that was relatively similar to that of their well-studied relative,the Common Cuckoo(Cuculus canorus).Tailorbird foster siblings were evicted from the nest rim.The cuckoo nestlings gained weight faster than host nestlings,and required 3–9 days longer time to fledge than host nestlings.Predation was high during the early stages of development,but the nestlings acquired a warning display around 11 days in the nest,after which none of the studied cuckoo nestlings were depredated.The cuckoos' begging display,which appeared more intense than that of host nestlings,was initially vocally similar with that of the host nestlings but began to diverge from the host sound output after day 9.Conclusions:The developmental data on Plaintive Cuckoo nestlings and their tailorbird host builds an important foundation for future work on the co-evolutionary interactions in this parasite–host system.

Experimental evidence that cuckoos preferentially parasitize host nests early in their laying cycle

Brood parasites,such as the Common Cuckoo(Cuculus canorus),rely on manipulating hosts from other species to raise their offspring.Selection should favor individuals that are able to identify and choose host nests that closely match the incubation stage of their own eggs.While intuitive,and supported by the findings of numerous longterm monitoring studies,experimental evidence of this remains sparse.By using video monitoring,we used three experimental groups to explore whether Common Cuckoos preferentially choose host Oriental Reed Warbler(Acrocephalus orientalis)nests that are early in their laying cycle.We found that Common Cuckoos preferentially parasitize nests of the host Oriental Reed Warbler that are earlier in their laying(less vs.more eggs)or nesting cycle(eggs vs.chicks),and videos of our experiments provide direct insights into their decision making process.Our results provide strong experimental evidence that Common Cuckoos are able to assess nesting stage and strategically choose nests that increase the likelihood of successful parasitism.

Do swallows(Hirundo daurica)use the visual cue of hatchling down-feathers to discriminate parasite alien nestlings?

Egg recognition is a variable but common anti-parasitism defense among different species of birds with brood parasites.In contrast,nestling recognition is rare.Very few studies have found nestling recognition in brood parasite hosts and determined the rejection mechanism behind this behavior.Hosts may use the number of hatchling downfeathers to reject parasite nestlings.We tested whether hatchling down-feathers is a visual cue for the red-rumped swallow,a host that can recognize and reject parasite nestlings.Our results indicated that red-rumped swallows do not recognize foreign nestlings based on hatchling down-feathers.The closed nest structure and hatchling morph may explain the absence of such a mechanism.None of the rejection mechanisms found in previous studies could explain the nestling recognition in swallows.Olfactory cues,tactile cues,or other visual cues,except for single nestling or hatchling down-feathers,may provide nestling recognition in red-rumped swallows.More study is needed to evaluate these possibilities.

Egg polymorphism and highly sensitive egg recognition ofcross-phenotypes in rufescent prinias Prinia rufescens as effectivedefenses against brood parasitism

INTRODUCTION Biological polymorphism is a striking phenomenon in nature where more than one morph of a trait has evolved within a single population(Galeotti et al.2003;Kilner 2006).Polymorphism can evolve and be maintained because each morph possesses fitness that reduces the frequency of one morph increasing the fitness of other morphs,and causes the evolution of all morphs by frequency-dependent selection(Majerus 1998;Cook et al.1999).