Why cuckoos should parasitize parrotbills by laying eggs randomly rather than laying eggs matching the egg appearance of parrotbill hosts?

The coevolutionary interaction between cuckoos and their hosts has been studied for a long time, but to date some puzzles still remain unsolved. Whether cuckoos parasitize their hosts by laying eggs randomly or matching the egg morphs of their hosts is one of the mysteries of the cuckoo problem. Scientists tend to believe that cuckoos lay eggs matching the appearance of host eggs due to selection caused by the ability of the hosts to recognize their own eggs.In this paper, we first review previous empirical studies to test this mystery and found no studies have provided direct evidence of cuckoos choosing to parasitize host nests where egg color and pattern match. We then present examples of unmatched cuckoo eggs in host nests and key life history traits of cuckoos, e.g. secretive behavior and rapid egg-laying and link them to cuckoo egg laying behavior. Finally we develop a conceptual model to demonstrate the egg laying behaviour of cuckoos and propose an empirical test that can provide direct evidence of the egg-laying properties of female cuckoos. We speculate that the degree of egg matching between cuckoo eggs and those of the host as detected by humans is caused by the ability of the hosts to recognize their own eggs, rather than the selection of matching host eggs by cuckoos. The case of Common Cuckoos(Cuculus canorus) and their parrotbill hosts(Paradoxornis alphonsianus), where it has been shown that both have evolved polymorphic eggs(mainly blue and white), was used to develop a conceptual model to demonstrate why cuckoos should utilize parrotbill hosts by laying eggs randomly rather than laying eggs matching the appearance of host eggs.In conclusion, we found no evidence for the hypothesis that cuckoos lay eggs based on own egg color matching that of the parrotbill-cuckoo system. We argue theoretically that laying eggs matching those of the hosts in this system violates a key trait of the life history of cuckoos and therefore should be maladaptive.

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.

Variaiton in the composition of small molecule compounds in the egg yolks of Asian Short-toed Larks between early and late broods

The egg yolks of birds contain most of the maternally derived materials required for embryo development and are an important factor influencing embryo development and offspring viability.Individual variation in egg-laying date frequently occurs in passerines inhabiting highly seasonal environments.Females laying in early and late stages of the breeding season encounter different environment temperatures and food conditions,which can affect the levels of metabolities in their bodies,thereby altering the transmission of these materials to the eggs.We test a hypothesis that yolk small molecule compounds of Asian Short-toed Lark(Alaudala cheleensis)could vary between early(mid-May)and late(mid-June)broods.Using the UHPLC-MS/MS method,683 compounds belonging to 21 compound groups are detected in the yolks.The contents of 18 compounds are significantly different between early and late broods.Ten differential compounds are significantly higher in the early laid eggs,among whichγ-aminobutyric acid,creatine,prostaglandins,palmitoleic acid,linoleic acid,and trans linoleic acid are related to low environment temperature response.The eggs laid in late stage exhibit significantly higher levels of 5-L-glutamyl-L-alanine andγ-glutamate-leucine,1,3-dimethyluric acid and mannose,which may be attributed to females in the late group consuming more insects.We suggest conducting a comprehensive investigation to reveal the yolk small molecule compounds mediated maternal effects on offspring phenotypes under varying ecological conditions.

A method of monitoring and locating eggs laid by breeding geese based on photoelectric sensing technology

On the current breeding goose farm,the detection of individual egg laying mainly depends on some judgement experiences of farm workers.At present,there have been some egg laying detection systems developed with images and weighing sensors,which only signal the eggs being laid,but no egg position being achieved.Meanwhile,the detection rate of the system is not high due to environment limitations like dim light of the goose barn.Therefore,to solve these problems mentioned above,an intelligent detection and positioning system is pro-posed by integrating technologies of the Radio Frequency(RF)and photoelectric sensors,together with the geometric calculation principle.In this research,individual egg laying information of breeding geese in a non-cage state was examined to improve the level of auto-matic detection and positioning in the field of breeder egg production.The results showed that an accurate detection and positioning of an egg in a nest filled with the artificial turf could be achieved under some conditions:the height of sensor is 3.5 cm from the bottom plate of the egg laying nest,the spacing of the photoresistor module is 5 cm,and the external light intensity is less than 110 LUX.It also shown that the error of the goose egg position recognition is 0.443 cm with a suitable level of straw in the nest.Therefore,the monitoring system and positioningmethod that was developed in this research could provide a reference for the analysis of individual egg laying behavior,and could result in an improvement in the automatic egg collection for the breeding geese production.