Do brood parasitic Common Cuckoos develop brood patches during the breeding season?

Many birds develop brood patches on their ventral apterium under hormonal regulation to effectively transmit body heat to eggs during incubation.The developed patch has several characteristics,including de-feathering,vascularization,and edema.However,little is known about whether avian brood parasites that do not incubate their eggs exhibit brood patch development during the breeding season.In this study,we measured the size of the ventral apterium in 114 Common Cuckoos(Cuculus canorus)captured in the field throughout the breeding season and examined the appearance of the ventral apterium to confirm the development of brood patches.We also examined whether morphological traits and various factors correlated with the size of the ventral apterium(sternal apterium and abdominal apterium)and how it changed during the breeding season.We found no clear signs of brood patch development in Common Cuckoos captured throughout the breeding season,indicating that they likely did not develop brood patches on the ventral apterium during this period.We also found that ventral apterium size was positively correlated with wing length and body weight.In addition,Common Cuckoos with newly growing feathers on the boundary of the ventral apterium with pteryla were frequently observed as seasons progressed to the end.In conclusion,Common Cuckoos exhibit neither brood patch development nor the vestigial characteristics of ancestral brood patches,except for the growth of feathers on boundary the ventral apterium.Further studies examining brood patches across different groups of avian brood parasites are valuable for enhancing our understanding of the developmental and physiological adaptations of avian brood parasites.

Oriental Reed Warblers do not abandon Common Cuckoo chicks during prolonged nestling periods

The Oriental Reed Warbler(Acrocephalus orientalis)is one of the most commonly used hosts for the parasitic Common Cuckoo(Cuculus canorus).However,as hosts that feed unrelated parasitic nestlings may suffer extra reproductive costs,they may be less willing to care for nestlings that have prolonged nestling periods.To test this hypothesis,the duration of feeding by Oriental Reed Warblers under natural conditions for their own nestlings was compared with the duration of feeding under natural conditions for Common Cuckoo nestlings and for artificially prolonged cuckoo nestlings.The results showed that Oriental Reed Warblers did not starve,drive away,or desert any of the nestlings in the experiment,and neither parent was left alone.Our experimental study indicates that both Oriental Reed Warbler parents were willing to care for nestlings with a prolonged nestling period(up to 30 days,twice the average duration time that the Oriental Reed Warblers fed their own chicks in natural conditions).However,further experiments and observations are required in other host bird species to examine whether both parents or one of the parents may exhibit the behavior of abandoning nestlings with a prolonged nestling period.

Reviewing 30 years of studies on the Common Cuckoo:accumulated knowledge and future perspectives

In Europe, eggs of the Common Cuckoo (Cuculus canorus) have been found in more than 125 different host species. However, very few species are frequently parasitized. The Cuckoo is divided into several distinct races termed gentes. Females of each gens specialize in parasitizing a particular host species. More than 20 such gentes are recognized in Europe. Each female Cuckoo lays eggs of constant appearance. Most gentes can be separated based on their distinct egg types, which in many cases mimic those of their hosts. Different gentes may occur in sympatry or may be separated geographically. Some gentes may occur in restricted parts of the host’s distribution area. These patterns raise some fundamental questions like: Why are some passerine species preferred as hosts while others are not? Why does a host population consist of individuals either accepting or rejecting Cuckoo eggs? Why is there marked variation in egg rejection behavior between various host populations? How distinct and host-specialized are Cuckoo gentes? These questions are discussed in relation to existing knowledge and future perspectives.

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.

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.

Identification of vocal individuality in male cuckoos using different analytical techniques

Background: Individuality in vocalizations may provide an effective tool for surveying populations of the Common Cuckoo(Cuculus canorus) but there remains few data on which technique to use to identify individuality. In this research, we compared the within-and between-individual variation in cuckoo calls using two different analytical methods, and discuss the feasibility of using call individuality to count male cuckoos within a population.Methods: We recorded vocalization from 13 males, and measured 15 spectro-temporal variables for each call. The majority of these call variables(n = 12) have greater variation between individuals than within individual. We first calculated the similarity(Pearson's R) for each paired calls in order to find a threshold that could distinguish calls emitted from the same or different males, and then counted the number of males based on this distinction. Second, we used the more widely accepted technique of discriminant function analysis(DFA) to identify individual male cuckoos, and compared the correct rate of classifying individuals between the two analytical methods.Results: Similarity of paired calls from the same male was significantly higher than from different males. Under a relatively broad threshold interval, we achieved a high(>90%) correct rate to distinguish calls and an accurate estimate of male numbers. Based on banded males(n = 3), we found the similarity of paired calls from different days was lower when compared with paired calls from the same day, but this change did not obscure individual identification, as similarity values of paired calls from different days were still larger than the threshold used to distinguish calls from the same or different males. DFA also yielded a high rate(91.9%) of correct classification of individuals.Conclusions: Our study suggests that identifying individual vocalizations can form the basis of an appropriate survey method for counting male cuckoos within a population, provided the performance of different analytical techniques are compared.

Linking individual attributes and host specialization in brood parasitic cuckoos

Generalist avian brood parasites vary considerably in their degree of host specialization(e.g.,number of hosts);some parasitize the nests of just a few host species,whereas others exploit more than 100 species.Several factors,including habitat range,habitat type,and geographic location,have been suggested to account for these variations.However,inter-specific differences in individual attributes,such as personality and plasticity,have rarely been considered as potential factors of such variation,despite their potential relationship to,for example,range expansion.Using cage experiments,we tested the hypothesis that parasitic species exploiting more host species may be more active and exploratory.To this end,we quantified behaviors exhibited by two Cuculus cuckoos(Common Cuckoo C.canorus and Oriental Cuckoo C.optatus)that vary greatly in their number of host species.Specifically,we evaluated exploratory behavior displayed by birds in the cage,such as the number of movements,head-turning,wing-flapping,and stepping.The Common Cuckoo,which has a higher number of host species,tended to exhibit higher levels of exploratory behaviors than the Oriental Cuckoo.Our study showed that the two cuckoo species exhibited different exploratory levels,as predicted by the differences in their number of hosts.Further studies regarding the causality between individual attributes and host specialization with improved experimental methodology would greatly enhance our understanding of the role of individual characteristics in the coevolution of avian brood parasites and their hosts.

Hawk mimicry does not reduce attacks of cuckoos by highly aggressive hosts

Background: Resemblance to raptors such as hawks(Accipiter spp.) is considered to be an adaptive strategy of cuckoos(Cuculus spp.), which has evolved to protect cuckoos against host attacks. However, the effectiveness of the mimicry remains controversial, and is not yet fully studied for highly aggressive hosts.Methods: We evaluated the effectiveness of sparrowhawk(Accipiter nisus) mimicry by common cuckoos(Cuculus canorus) in oriental reed warblers(Acrocephaus orientalis), which are highly aggressive hosts. Using a both the single and the paired dummy experiment, defense behaviors and attack intensities of oriental reed warblers against common cuckoos, sparrowhawks and oriental turtle doves(Streptopelia orientalis) were assessed.Results: Oriental reed warblers exhibit strong nest defense behaviors, and such behaviors do not change with breeding stage(i.e., egg stage and nestling stage). Furthermore, assistance from conspecific helpers may increase attack intensities. However, they were deterred from mobbing overall by the presence of the hawk.Conclusions: Oriental reed warblers are able to distinguish cuckoos from harmless doves. However, they may be deterred from mobbing by the presence of the predatory hawk, suggesting hawk mimicry may be ineffective and does not reduce attacks of cuckoos by highly aggressive hosts.

中国大杜鹃的鸣声(英文)

一直以来认为广布欧洲大陆和亚洲大陆的大杜鹃 ,其鸣声在地区之间无差异 ,而分布在亚洲的大杜鹃的鸣声至今未有系统的研究报道。本文以分布在中国北部的大杜鹃指名亚种和新疆亚种的广告鸣叫为主要研究对象 ,将其与在四川和云南省分布的大杜鹃华西亚种以及分布在朝鲜、日本、俄罗斯和英格兰的大杜鹃指名亚种的广告鸣叫进行了初步比较。在中国分布的大杜鹃有五种鸣叫类型。中国所有采集地大杜鹃的广告鸣叫都由两个音节组成 ,并且与英国分布种群的广告鸣叫很相似。

形态相似的4种杜鹃的鉴别

大杜鹃Cuculus canorus,中杜鹃C.saturatus,小杜鹃C.poliocephalus和四声杜鹃C.micropterus通过鸣声可快速鉴别,但这4种杜鹃的形态非常相似,在体长、翅长、尾长、喙长等身体量度指标之间的变异范围有重叠或数值非常接近,鉴别困难.为方便野外鉴别,文章给出了这4种杜鹃的鉴别性外部形态特征及其简易图片辨识方法.4种形态相似的杜鹃种类特征如下:四声杜鹃的尾羽具宽阔的近端黑斑,中杜鹃翼下覆羽的横斑少而不显,大杜鹃的腹部横纹细,而小杜鹃的腹部横纹粗.小杜鹃与四声杜鹃可通过体长、翅长和喙长区分,大杜鹃和小杜鹃也可通过翅长区分.

大杜鹃寄生白鹡鸰巢的实际案例

目前,众多寄生性杜鹃里,大杜鹃(Cuculus canorus)的宿主种类最多,白鹡鸰(Motacilla alba)作为其中的宿主之一,尚未发现其寄生巢、卵的相关数据。2019—2021年,通过在贵州六枝地区搜索并记录白鹡鸰巢的方法,收集白鹡鸰相关数据,以了解白鹡鸰巢址情况及基础繁殖参数,并于2020年6月16日在白鹡鸰巢中首次发现大杜鹃的寄生卵。通过模型卵识别实验,检测白鹡鸰卵识别能力,拒绝率较高,表明白鹡鸰可能已具备识别并拒绝外来卵的能力。对大杜鹃寄生巢及卵的记录,补充了大杜鹃—白鹡鸰寄生系统中寄生卵相关数据的空缺,初步了解该寄生系统中大杜鹃卵的模拟程度。

大杜鹃对家燕的巢寄生

了解杜鹃(Cuculus spp.)对不同宿主鸟类的巢寄生,是研究杜鹃与其宿主之间协同进化的重要基础资料。大杜鹃(Cuculus canorus)和家燕(Hirundo rustica)分布遍及全国,且为同域分布,但两者之间的寄生现象尚未有过系统调查。2012年和2014年4~8月,对繁殖于吉林市昌邑区桦皮厂镇(34°58′44.18″N,126°13′26.83″E,海拔184 m)和海南岛的家燕种群进行调查,结果表明,吉林市昌邑区桦皮厂镇家燕种群的寄生率为2.4%(1/42),而在海南岛所调查的1 719个家燕巢未发现杜鹃寄生现象。同时在网络上搜集家燕巢寄生的报道案例,共记录到13巢家燕被大杜鹃寄生繁殖,均发生在北方的家燕种群。

Personality of hosts and their brood parasites

Brood parasites such as the common cuckoo Cuculus canorus exploit the parental abilities of their hosts,hosts avoid brood parasitism and predation by showing specific behavior such as loss of feathers,emission of fear screams and contact calls,displaying wriggle behavior to avoid hosts or potential prey,pecking at hosts and prey,and expressing tonic immobility(showing behavior like feigning death or rapid escape from predators and brood parasites).These aspects of escape behavior are consistent for individuals but also among sites,seasons,and years.Escape behavior expressed in response to a broad range of cuckoo hosts and prey are consistently used against capture by humans,but also hosts and brood parasites and predators and their prey.An interspecific comparative phylogenetic analysis of escape behavior by hosts and their brood parasites and prey and their predators revealed evidence of consistent behavior when encountering potential parasites or predators.We hypothesize that personality axes such as those ranging from fearfulness to being bold,and from neophobic to curiosity response in brood parasites constitute important components of defense against brood parasitism that reduces the overall risk of parasitism.

大杜鹃对北红尾鸲的放牧行为

在宿主的寄生防御压力下,鸟类巢寄生者通常会进化出一系列有效的寄生行为以提高其自身的繁殖适合度。以往研究发现,部分巢寄生者可能具有类似人类的“放牧”行为,即通过破坏或捕食不适合寄生的宿主巢,促使其重新筑巢以获取新的寄生机会。然而,对于其野外行为事件的报道并不多见。2018年5至8月,在贵州六枝地区,通过对宿主北红尾鸲(Phoenicurus auroreus)的巢进行录像监控,首次记录到大杜鹃(Cuculus canorus)对正在孵卵的北红尾鸲的放牧行为。进一步查阅了大杜鹃寄生系统中已有的放牧案例,说明放牧行为很可能是大杜鹃普遍采用的一种寄生策略。

大杜鹃和东方大苇莺卵的人工孵卵期和孵化率比较

大杜鹃(Cuculus canorus)是一种专性巢寄生鸟类,进化出了一系列适应对策,如雏鸟普遍出壳较早等,以更好适应寄生生活。本研究使用恒温自动孵化箱对25枚大杜鹃卵和20枚其宿主东方大苇莺(Acrocephalus orientalis)卵进行人工孵化,并对孵卵期的卵重进行连续测量。结果表明,在人工孵化条件下,大杜鹃卵的孵化率(76%)极显著高于东方大苇莺(40%)(χ~2=25.144,df=1,P<0.01)。尽管大杜鹃的卵鲜重(t=7.447,df=43,P<0.01)和卵体积(t=8.817,df=43,P<0.01)均极显著大于东方大苇莺,但两种鸟卵的孵卵期不存在显著性差异(t=1.006,df=16,P>0.05)。

大杜鹃雌鸟鸣声的日节律

本文描述了三个地区大杜鹃(Cuculus canorus)雌鸟鸣声的日节律。通过在北京野鸭湖湿地公园(2017年5月7日至7月8日)、辽宁辽河口自然保护区(2018年6月28日至7月29日)和吉林大岗子林场(2018年5月17日至7月10日)分别布设自动录音机10台、10台和8台,连续记录繁殖季大杜鹃的鸣声。共录到2777次大杜鹃雌鸟的鸣叫。其中,1431次来自北京野鸭湖湿地公园,1222次来自辽宁辽河口自然保护区,124次来自吉林大岗子林场。野鸭湖湿地公园和辽河口自然保护区的大杜鹃雌鸟在日出时段出现鸣叫的高峰,而大岗子林场的大杜鹃在日出和日落时段各有一个鸣叫的高峰。通过比较大杜鹃雌鸟鸣声的日节律和大杜鹃产卵时间的日节律,本研究认为在上述地区大杜鹃雌鸟鸣叫的功能更可能是宣示领域和吸引异性,而非恐吓宿主。本研究有助于进一步了解大杜鹃雌鸟鸣声的功能。