Csaba Moskát

Eötvös Loránd University · MTA-ELTE-MTM Ecology Research Group

Sex-limited polymorphism has evolved in many species including our own. Yet, we lack a detailed understanding of the underlying genetic variation and evolutionary processes at work. The brood parasitic common cuckoo ( Cuculus canorus ) is a prime example of female-limited color polymorphism, where adult males are monochromatic gray and females exhi...

Mimicry is a widespread phenomenon whereby predatory or parasitic individuals can access unsuspecting prey or hosts for the former’s benefit. For example, brood parasitic common cuckoos (Cuculus canorus) evolved several adaptations to trick hosts, including host-mimetic eggs, a barred chest plumage resembling the predatory Eurasian sparrowhawk (Acc...

Egg rejection is an effective and widespread antiparasitic defense to eliminate foreign eggs from the nests of hosts of brood parasitic birds. Several lines of observational and critical experimental evidence support a role for learning by hosts in the recognition of parasitic versus own eggs; specifically, individual hosts that have had prior or c...

In many bird species loud broadcast calls serve as aggressive signals with a large effective radius, whereas soft calls may indicate aggression at a closer distance, and are often directed at a nearby conspecific individual. Male common cuckoos (Cuculus canorus) are famous for their simple cu-coo calls, which are long-range broadcast calls, uttered...

Acoustic communication of animals often contains two types of vocalizations: loud sounds for long-range, and soft sounds for short-range signalling. Brood parasitic common cuckoos (Cuculus canorus) are suitable study objects for research of acoustic signalling as they have a simple acoustic repertoire, of which the loud territorial advertisement ca...

When acoustic communication signals are distorted, receivers may misunderstand the signal, rendering it ineffective. Common cuckoos (Cuculus canorus) are popularly known for the males' simple, two-note advertisement calls, the "cu-coo" used for declaring the male's breeding territories. Cuckoos do not learn their calls (vocal non-learners), so they...

Duetting is a coordinated form of acoustic communication with participants uttering calls or songs simultaneously and/or sequentially. Duetting is often observed in pair-bonded species, with mated females and males both contributing to the communal vocal output. We observed duetting between the sexes in the common cuckoo (Cuculus canorus), an oblig...

The brood parasitic Common Cuckoo Cuculus canorus is best known for its two-note "cu-coo" call which is almost continuously uttered by male during the breeding season and can be heard across long distances in the field. Although the informative value of the cuckoo call was intensively investigated recently, it is still not clear whether call charac...

Ongoing global change has had biologically impactful effects on the breeding phenology of both resident and migratory bird species, including avian hosts and their obligate brood parasites. We analyzed a local breeding site’s weather changes in Central Hungary and shifts in the reproductive timing of two interacting long-distance migratory bird spe...

To avoid mobbing attacks by their hosts during egg laying, some avian brood parasites have evolved traits to visually and/or acoustically resemble predator(s) of their hosts. Prior work established that reed warblers (Acrocephalus scirpaceus), a small host species of the brood parasitic common cuckoo (Cuculus canorus), delayed returning to the nest...

The obligate brood parasitic common cuckoo (Cuculus canorus) is best known for its two-note “cu-coo” call, which is uttered repeatedly by adult males during the breeding season. This call advertises the male’s claim for his territory. A rare, aberrant version (“cu-kee”) was discovered in a population of cuckoos in central Hungary. In a playback exp...

Female-only colour polymorphism is rare in birds, but occurs in brood parasitic cuckoos (Cuculidae). Obligate brood parasites leave incubation and parental care to other species (hosts), so female-female interactions can play a role in how parasites guard critical resources (host nests) within their laying areas. The plumage of adult female common...

It is well known that avian brood parasites lay their eggs in the nests of other bird species, called hosts. It remains less clear, however, just how parasites are able to recognize their hosts and identify the exact location of the appropriate nests to lay their eggs in. While previous studies attributed high importance to visual signals in findin...

One of the most effective defenses against avian brood parasitism is the rejection of the foreign egg from the host's nest. Until recently, most studies have tested whether hosts discriminate between own and foreign eggs based on the absolute differences in avian-perceivable eggshell coloration and maculation. However, recent studies suggest that h...

The two-note call of the male common cuckoo (Cuculus canorus), the so-called “cu-coo”, is well known to people as a natural and cultural signal. However, the so-called “bubbling” call of the female cuckoo is almost unknown to most, and its function in the social organization of cuckoos remains understudied. We carried out a study of a possible intr...

Obligate brood parasitic birds have evolved a rare avian strategy for reproduction by laying eggs in the nests of other species. In doing so, their breeding ranges, but not necessarily their foraging habitats, have become intimately related to the nesting territories of their hosts. We studied home range sizes and distribution patterns in Common Cu...

A host that has been targeted by an avian brood parasite can recover most of its potential fitness loss by ejecting the foreign egg(s) from its nest. The propensity for some hosts to engage in egg rejection behavior has put selective pressure on their parasites to evolve mimetic eggshells resembling the host's own shell colors and maculation. In tu...

We tagged 12 adult Common Cuckoos (Cuculus canorus) with non-platform terminal transmitter (non-PTT) GPS-UHF telemetry at their breeding grounds in Hungary. One male and two female Cuckoos (one of them twice) were again observed in subsequent years, and GPS fixes documented their migration routes to and from Africa, as far south as Namibia. All fou...

Common cuckoos (Cuculus canorus) are best known for their simple two-note calls ("cu-coo"), which are uttered only by males during the breeding season. A previous playback study revealed that territorial males were more tolerant toward playbacks of the calls of familiar, neighbouring individuals than toward unfamiliar, stranger simulated intruders,...

The common cuckoo (Cuculus canorus) is an avian brood parasite, laying its eggs in the nests of other bird species, where these hosts incubate the parasitic eggs, feed and rear the nestlings. The appearance of a cuckoo egg in a host nest may change the bacterial community in the nest. This may have consequences on the hatchability of host eggs, eve...

Identification of the 177 bacterial strains isolated from the eggshells of common cuckoo and great reed warbler, based on BLAST analysis of the 16S rRNA gene sequences. (PDF)

Relative abundance of four bacterial phyla in samples. (TIF)

Maximum Likelihood tree of the eggshell bacterial isolates from parasitized nests. (TIF)

The characteristics of common cuckoo (Cuculus canorus) and host eggs are widely thought to have coevolved over time, but few studies have tested this prediction. We compared cuckoo eggs with those of its primary host, the great reed warbler (Acrocephalus arundinaceus) from four time periods spanning >100 years (between 1900 and 2014), and studied i...

Common cuckoos, Cuculus canorus, are brood parasites: they lay their eggs in the nests of other bird species, and let these hosts incubate their eggs and feed and rear the nestlings. Although cuckoos do not show parental care, they demonstrate complex social interactions, including territorial behaviours and male–male aggression. Cuckoos have a wel...

Common cuckoos Cuculus canorus are obligate brood parasites that lay their eggs in the nests of other (host) species. To increase the likelihood of successful parasitism, common cuckoos lay eggs with thicker and structurally stronger eggshells than those of their hosts and non-parasitic relatives. Although hatching from thicker eggshells requires g...

Provisioning of artificial nest-boxes proved to be an effective method to make suitable breeding sites for secondary cavity nester birds due to the lack of natural hollows. The European roller (Coracias garrulus) is a threatened bird species in Europe, which suffered a serious decline throughout its breeding range. Changing agricultural practices s...

Egg rejection is the best studied behavioral adaptation by hosts to avian brood parasitism. Investigations of the mechanism(s) by which a host accomplishes the task of perceiving and deciding to reject a foreign egg have been a hotbed of debate and discovery for decades. The two most often tested cognitive explanations for this behavior are: (1) th...

Chicks of avian brood parasites either cohabit with host nestlings (e.g., cowbirds, non-evictor cuckoos) or eventually eliminate their potential competitors and are raised as the sole inhabitants of the foster parents’ nest. This latter phenomenon, termed as direct killing, involves the young brood parasitic chick evicting all other eggs or hatchli...

Distinctive individual vocalizations are advantageous in several social contexts. Both genetic and environmental effects are responsible for this phenomenon resulting in different frequencies and time domains of sounds in birds. This individuality can be utilized in breeding bird censuses and abundance estimates. In this study we explored the indiv...

Capsule Brood parasitic Common Cuckoo Cuculus canorus chicks hatch earlier than the nestlings of their Great Reed Warbler Acrocephalus arundinaceus hosts, but hatching priority is less consistent when Cuckoo eggs are laid after the onset of host incubation. Aim To reveal by field observations what the optimal stage is for Cuckoos to lay their eggs...

European rollers (Coracias garrulus) were almost extinct from large parts of Hungary in the 1970–1980s. However up till now their population size increased considerably, mainly due to a nature conservation campaign, supplying artificial nest-boxes for breeding. We studied which factors affected rollers’ occurrences at the landscape scale in souther...

Common Cuckoos (Cuculus canorus) are obligate brood parasites that lay their eggs in nests of other species and use these hosts to raise their parasitic offspring. Two key adaptations that increase their reproductive success are (1) the capacity for cuckoos to lay large numbers of eggs and thereby parasitize many nests per year, and (2) the ability...

Obligate brood parasitic birds exploit their hosts to provide care for unrelated young in the nest. Potential hosts can reduce the cost of parasitism by rejecting foreign eggs from the nest. Observational, comparative, and experimental studies have concluded that most hosts use the coloration and patterning of eggshells to discriminate between own...

Experimentation is at the heart of classical and modern behavioral ecology research. The manipulation of natural cues allows us to establish causation between aspects of the environment, both internal and external to organisms, and their effects on animals' behaviors. In recognition systems research, including the quest to understand the coevolutio...

The coevolutionary process among avian brood parasites and their hosts involves stepwise changes induced by the antagonistic selection pressures of one on the other. As long-term data on an evolutionary scale is almost impossible to obtain, most studies can only show snapshots of such processes. Information on host behaviour, such as changes in egg...

Capsule Rollers showed slightly higher breeding performance in farmland mosaics than in natural grasslands in southern Hungary, where both habitats were supplied with nest-boxes. Aim To establish which factors affect Rollers’ breeding success in agricultural and their more traditional grassland habitats. Methods Rollers’ reproductive success in f...

An unexpected expansion of the Eastern Imperial Eagle (Aquila heliaca) population was observed in East Hungary from mountainous habitat into lowlands from 1989 onwards. Here the population markedly increased from 2 to 59 breeding pairs by 2006, while the mountainous population remained more or less stable with 12-17 breeding pairs. At the beginning...

Background Many potential hosts of social parasites recognize and reject foreign intruders, and reduce or altogether escape the negative impacts of parasitism. The ontogenetic basis of whether and how avian hosts recognize their own and the brood parasitic eggs remains unclear. By repeatedly parasitizing the same hosts with a consistent parasitic e...

Great reed warblers (Acrocephalus arundinaceus) are frequently parasitized by egg-mimetic common cuckoos (Cuculus canorus) in Hungary, and these hosts reject about a third of parasitic eggs. The timing of parasitism is important, in that the probability of rejection decreases with advancing breeding stages in this host. Also, egg rejection is more...

Egg discrimination by hosts is an antiparasitic defence to reject foreign eggs from the nest. Even when mimetic, the presence of brood parasitic egg(s) typically alters the overall similarity of all eggs in a clutch, producing a discordant clutch compared to more homogenous clutches of composed only of hosts’ own eggs. In multiple parasitism, the m...

Many hosts have evolved diverse cognitive mechanisms to recognize and reduce the cost of social parasitism. For example, great reed warblers Acrocephalus arundinaceus can accurately reject closely mimetic eggs of brood parasitic common cuckoos Cuculus canorus. Yet, these same hosts are less effective at identifying and rejecting parasitism when the...

Common Cuckoos (Cuculus canorus) parasitize nests of small passerines. The Cuckoo chicks cause the death of their nest-mates when evicting eggs or nestlings from the nests; conse- quently, hosts suffer from a high loss of reproduction. Host adaptations against parasitism, e.g., by egg discrimination behavior, and cuckoo counter-adaptations to hos...

To avoid competition for parental care, brood-parasitic Common Cuckoo (Cuculus canorus) nestlings evict all of the host's eggs and nestlings within a few days after hatching. Little is known about the physiological effects of eviction behavior on the cuckoo nestling's oxidative balance or about age-related variation in plasma oxidative status and t...

Sex allocation theory and empirical evidence both suggest that natural selection should favour maternal control of offspring sex ratio in relation to their ability to invest in the offspring. Generalist parasites constitute a particularly interesting group to test this theory as different females commonly utilize different host species showing larg...

Chicks of the brood parasitic common cuckoo (Cuculus canorus) typically monopolize host parental care by evicting all eggs and nestmates from the nest. To assess the benefits of parasitic eviction behaviour throughout the full nestling period, we generated mixed broods of one cuckoo and one great reed warbler (Acrocephalus arundinaceus) to study ho...

The size, patterning and coloration of bird eggs may signal different information content to nest owners, mates, predators, hosts, or brood parasites. Recent studies suggested that the pigmentation at one pole of the typically asymmetrical avian egg plays a critical role in the discrimination of own and foreign eggs by several host species parasiti...

Avian brood parasites lay their eggs in other birds' nests and impose considerable fitness costs on their hosts. Historically and scientifically, the best studied example of circumventing host defences is the mimicry of host eggshell colour by the common cuckoo (Cuculus canorus). Yet the chemical basis of eggshell colour similarity, which impacts h...

Evolutionary adaptations are required by common cuckoos Cuculus canorus to match host eggs. Hosts may discriminate against alien eggs; hence, accurate matching of the parasite egg to the hosts' is essential. Egg shape is the least-studied component of egg mimicry, and it may also have other functions: an optimal egg shape is necessary for effective...

Obligate brood parasitic birds lay their eggs in nests of other species and parasite eggs typically have evolved greater structural strength relative to host eggs. Increased mechanical strength of the parasite eggshell is an adaptation that can interfere with puncture ejection behaviours of discriminating hosts. We investigated whether hardness of...

Hosts of the common cuckoo (Cuculus canorus), an avian brood parasite, develop antiparasite defense mechanisms to increase their reproductive success. Ejection of the parasite egg and desertion of the parasitized nest are the most typical adaptations in response to brood parasitism, but nest desertion may also occur in response to partial clutch re...

1. Why are some common and apparently suitable resources avoided by potential users? This interesting ecological and evolutionary conundrum is vividly illustrated by obligate brood parasites. Parasitic birds lay their eggs into nests of a wide range of host species, including many rare ones, but do not parasitize some commonly co-occurring potentia...

Avian brood parasites greatly reduce the reproductive success of their hosts. Empirical studies have demonstrated that some hosts have evolved defenses against parasitism like an ability to recognize and reject parasitic eggs that are dissimilar to their own eggs. Detailed mechanisms of how hosts recognize parasitism still remain unknown, but recen...

The study of avian eggshell structure, including composition, pigmentation, thickness, and strength, has important ecological and economic implications. Previous investigators have used a variety of techniques to derive either direct measures or indirect estimates of eggshell thickness. Assessing the repeatability and method agreement of different...

The offspring of brood parasitic birds benefit from hatching earlier than host young. A proposed but little-known strategy to achieve this is 'internal incubation', by retaining the egg in the oviduct for an additional 24 h. To test this, we quantified the stage of embryo development at laying in four brood parasitic birds (European cuckoo, Cuculus...

Parasites require synchrony with their hosts so if host timing changes with climate change, some parasites may decline and eventually go extinct. Residents and short-distance migrant hosts of the brood parasitic common cuckoo, Cuculus canorus, have advanced their phenology in response to climate change more than long-distance migrants, including th...

Many avian hosts have evolved antiparasite defence mechanisms, including egg rejection, to reduce the costs of brood parasitism. The two main alternative cognitive mechanisms of egg discrimination are thought to be based on the perceived discordancy of eggs in a clutch or the use of recognition templates by hosts. Our experiments reveal that the gr...

Reproductive success of raptor species is significantly affected by the quantity and/or quality of available prey. In our study we analysed prey composition of breeding imperial eagles (Aquila heliaca) in East Hungary, where 434 nesting events in 81 different territories had been monitored between 1995 and 2004. We identified 1297 prey items origin...

Female common cuckoos Cuculus canorus lay eggs every other day and typically parasitise nests before the hosts complete their clutches. When laying strategy of the cuckoo is well-synchronised with that of the host, the reproductive success of the parasite may increase. In contrast, when parasitism frequencies are high, cuckoo females might be less...

The developmental rate of cuckoo embryos and their hatching size is greater than that of host species, which may require more nutrient resources in the egg and more intensive gas exchange during development. In the present study, we compared various egg characteristics of a brood parasite, the common cuckoo Cuculus canorus, and its frequent host, t...

Hatchlings of the obligate brood parasite common cuckoo Cuculus canorus typically evict eggs and nestmates but, rarely, host and parasite nestlings may grow up together. As part of previous experiments, we manipulated host clutches by inducing two great reed warbler Acrocephalus arundinaceus and one parasite young to share a nest from 4 days postha...

Chicks of virulent brood parasitic birds eliminate their nestmates and avoid costly competition for foster parental care. Yet, efforts to evict nest contents by the blind and naked common cuckoo Cuculus canorus hatchling are counterintuitive as both adult parasites and large older cuckoo chicks appear to be better suited to tossing the eggs and you...

The common cuckoo Cuculus canorus parasitism greatly reduces the reproductive success of its hosts and imposes strong selection pressure for hosts to evolve defences against parasitism, such as the ability to recognize and reject dissimilar parasitic eggs, which, in turn, selects for better egg mimicry by the cuckoo. In the co-evolutionary interact...

In birds, multiple parasitism is the laying of two or more eggs by one or more parasitic females in a single host nest. Several cognitive mechanisms may explain how multiple parasitism could affect parasite egg discrimination by hosts. Rejection based on discordance predicts that multiple parasitism provides a perceptually more error-prone way for...

There is widespread evidence that individuals within and among host populations are not evenly parasitized by Common Cuckoos (Cuculus canorus). We first investigated whether the song and nest size of a host species, the Great Reed Warbler (Acrocephalus arundinaceus), reveal information on parental abilities and level of defense against Common Cucko...

The Common Cuckoo (Cuculus canorus) is the only widely spread brood parasite in Europe. It is a successful species in the sense that it has already parasited most (perhaps all?) of the suitable host species all over Europe. On the other hand parasitised hosts during the contact with the Cuckoo developed antiparasite defence against this brood paras...

In Hungary an unusually high rate of parasitism on the great reed warbler Acrocephalus arundinaceus by the common cuckoo Cuculus canorus has been maintained for at least the last one hundred years. We evaluated parasitism rate, antiparasite defence and genetic differentiation among Hungarian great reed warblers at three sites located 40–130 km from...

Common cuckoo (Cuculus canorus) parasitism drastically reduces the reproductive success of their hosts and selects for host discrimination of cuckoo eggs. In a second stage of anti-parasite adaptation, once cuckoos can lay eggs that mimic those of their hosts, a high uniformity of host egg appearance within a clutch may favour cuckoo egg discrimina...

Egg discrimination in hosts of the common cuckoo Cuculus canorus is frequently studied by experimental parasitism, using model cuckoo eggs. We compared egg rejection behaviour of the great reed warbler Acrocephalus arundinaceus to either model cuckoo eggs made of plastic or painted real host eggs. We simultaneously parasitised host nests by two dif...

The risk of cuckoo Cuculus canorus parasitism for great reed warbler Acrocephalus arundinaceus nests was evaluated in respect to nest and nest site structure in the reedbeds along canals in central Hungary, In total 90 nests were analysed, from which 31 remained unparasitised. 37 were single parasitised and 22 multiple parasitised. Multiple discrim...

Many hosts of the common cuckoo (Cuculus canorus) exhibit egg recognition, and reject parasitic eggs. How do hosts discriminate cuckoo eggs from their own? Hosts might be able to recognize their own eggs using the specific pigment pattern on the outer eggshell surface, which may serve as a cue for recognition. We tested if patterns of egg pigments...

Obligate avian brood parasitism typically involves one of 2 strategies: parasite chicks are either 1) virulent and evict all other eggs and nest mates to be raised alone or 2) more tolerant and share foster parental care with host chicks for some or the entirety of the nestling period. We studied the consequences of experimentally forced mixed broo...

We studied the eviction behaviour of common cuckoo Cuculus canorus chicks by video recording at nests of great reed warblers Acrocephalus arundinaceus and reed warblers Acrocephalus scirpaceus. There were no significant differences in hatching mass and age at first eviction between cuckoos reared by either host. However, mass at eviction had a sign...

Common cuckoos (Cuculus canorus) are obligate brood parasites, laying eggs into nests of small songbirds. The cuckoo hatchling evicts all eggs and young from a nest, eliminating hosts' breeding success. Despite the consistently high costs of parasitism by common cuckoos, great reed warbler (Acrocephalus arundinaceus) hosts sometime accept and other...

Prevailing theory predicts that lower levels of intra-clutch variation in host eggs facilitate the detection of brood parasitism. We assessed egg matching using both human vision and UV-VIS spectrophotometry and then followed the nest fate of great reed warblers naturally parasitised by European cuckoos. Rejection was predicted by the following thr...

Prevailing theory assumes cuckoos lay at random among host nests within a population, although it has been suggested that cuckoos could choose large nests and relatively active pairs within host populations. We tested the hypothesis that egg matching could be improved by cuckoos choosing nests in which host eggs more closely match their own, by ass...

Site occupancy of migrating and breeding lcterine warblers was studied with respect to unoccupied randomly chosen sites in a willow and poplar mixed forest along the river Danube in Hungary Multivariate discriminant analysis revealed 4 different zones in the ordination diagram exclusive breeding zone, exclusive migrating zone overlapping zone, and...