Interspecific Brood Parasitism Research Articles

The effect of Common Cuckoo parasitism on the annual productivity of a host population

Avian interspecific brood parasitism is an excellent system for studying coevolutionary processes in nature because brood parasites directly affect host reproductive success. Most research on avian brood parasitism has, therefore, focused primarily on specific host anti-parasite behaviours and parasite counter-adaptations. However, the population-level consequences of brood parasitism for host species are poorly understood. This study investigated the effect of Common Cuckoo (Cuculus canorus) parasitism on the productivity of a local population of the Great Reed Warbler (Acrocephalus arundinaceus) host in south-western Slovakia. A total of 495 females nesting at the studied site successfully fledged 1321 of their own young and 63 young of the Common Cuckoo over the course of 15 years (2008–2022), and the annual rate of successful parasitism ranged from 18% to 44% over this period. As predicted, higher rates of successful cuckoo parasitism significantly reduced the annual productivity of the local Great Reed Warbler population, and its contribution to decreased host reproductive success was at about the same rate as overall nest failure caused by predation and other environmental factors. Such a heavily parasitized population was probably maintained by immigrants from other populations and density-dependent selection, which is also consistent with source–sink dynamics. However, further long-term studies monitoring parasitized populations are required to confirm these findings.

Three species of birds in one nest

Some birds build nests in which to lay eggs and rear offspring. Although occasionally associated with intra- or interspecific brood parasites, a single nest is generally occupied by the parents and offspring of one (and the same) species. However, in Xinjiang, China, we observed multiple breeding pairs of two sparrow species (saxaul sparrow [Passer ammodendri] and Spanish sparrow [Passer hispaniolensis]) inhabiting the nest of a long-legged buzzard (Buteo rufinus). On 4 April 2022, we found a long-legged buzzard's nest in a Euphrates poplar tree (Populus euphratica), near Dongdao Lake at the southern edge of the Gurbantunggut Desert in northwestern China. The nest was composed of poplar and tamarisk (Tamarix sp) branches (on the outside) and twigs (for the base). As we approached this Euphrates poplar, the buzzard was on alert. To our surprise, we detected a few holes in the middle and lower parts of the nest, in which lived several pairs of both sparrow species. According to our previous observations, neither P ammodendri nor P hispaniolensis are cavity-nesting birds, as they typically build their own cup-like nests.

First documented case of Tawny Pipit <em>Anthus campestris</em> nest parasitism by Common Cuckoo <em>Cuculus canorus</em> in Spanish steppes

Interspecific brood or nest parasitism is a relatively common breeding behavior in birds. Through this reproductive tactic, brood-parasites avoid the costs associated with raising and maintaining chicks by laying their eggs in the nests of the host species in which they are specialized. The common cuckoo (Cuculus canorus) follows this brood parasite strategy. Female cuckoos lay their eggs in the nests of other bird species, mimicking egg shape, size, and color of the host species. In this paper we report the first documented case of parasitism of tawny pipit nests by the common cuckoo in Spanish steppe habitats, where no record of parasitism on this species has been reported to date.

A Mixed Brood of Coal Tits Periparus ater and Blue Tits Cyanistes caeruleus in Central Portugal

Mixed-species broods appear to be an uncommon phenomenon in altricial birds. In secondary hole-nesting birds, such as tits (Paridae), mixed-species clutches occur as a consequence of facultative interspecific brood parasitism or as a byproduct of nest takeover. Here, we report a case of a mixed-species brood composed of one Coal Tit Periparus ater and three Blue Tit Cyanistes caeruleus nestlings that was successfully raised by a Blue Tit pair. The foreign Coal Tit nestling received more food than its Blue Tit nestmates, possibly resulting in a larger tarsus length compared to other Coal Tit nestlings from a regular single-species brood in the same forest.

Rejection of Conspecific Eggs Associated with the Appearance of Eggs, in the Azure-Winged Magpie Cyanopica cyanus in Korea

Avian brood parasitism is a reproductive strategy in which a parasitic species lays its eggs in the nests of a host. In response to parasitism, hosts have evolved various defence strategies. One of the host defences against intraspecific and interspecific brood parasitism is to distinguish parasitic eggs based on intraclutch variation in egg appearance. Hosts can improve their ability to discriminate parasitic eggs by lowering the degree of their intraclutch variation in egg appearance. Therefore, intraclutch variation may affect the egg rejection behaviour of hosts. In this study, we conducted experiments to study egg recognition and rejection behavior for mimetic eggs in Azure-winged Magpies Cyanopica cyanus in Korea. We also investigated the level of variation in egg appearance (egg color, spottiness and volume) in order to explore whether the degree of this variation is associated with the rejection decision. We found that there were no differences in egg coloration or spottiness between the rejecter and accepter. However, we found that intraclutch egg volume variation in rejecters was significantly lower than that in accepters, indicating that the Azure-winged Magpie is likely to recognize its own eggs by lowering its intraclutch variation in egg volume as a defensive strategy against brood parasitism. This study suggests that the Azure-winged Magpie use not the differences in egg coloration but egg volume to discriminate and reject closely mimetic conspecific eggs.

Nest predation, brood parasitism and the reproductive success of the masked laughingthrush Garrulax perspicillatus in the rural habitat of central China

Knowledge of nest site selection and reproductive ecology is fundamental to understanding the evolution of life history traits and developing species conservation strategies. However, life history traits of species in the genus Garrulax are poorly known. Particularly, research on the breeding biology of Garrulax perspicillatus in their natural habitat and comparison between populations in different environments (rural vs urban) are lacking. We presented data of nest site selection and breeding ecology of Masked Laughingthrush in central China during 2021, and made a detailed investigation on nest predation and interspecific brood parasitism. The breeding season began from March and ended in August. Most nests were built on Sulphur Bamboo ( Phyllostachys sulphurea). First egg laying occurred between late March and late July. Incubation period lasted 13.9 days (±0.3 SE; 13–15) and nestling period of 13.1 days (±0.2 SE; 12–15). Average clutch size was 3.8 eggs (±0.1 SE; 3–7), and brood size at fledging was 2.7 young (±0.2 SE; 1–4). Overall, 36.2% of nesting attempts successfully fledged at least one young. Nest predation (0% in March, 38.2% in April, 30.0% in May, 20.0% in June and 27.3% in July) and interspecific brood parasitism (13.3% in May, 40.0% in June and 36.4% in July) were two main reasons for nest failure. This is the first study that provided detailed information of breeding ecology of Masked Laughingthrush in rural habitat, and we discussed the difference of life history traits between urban and rural habitats.

Louisiana Black-bellied Whistling-Duck clutch characteristics in the presence of conspecific and interspecific brood parasitism

Black-bellied Whistling-Ducks (<em>Dendrocygna autumnalis</em>; Whistling-Duck) are undergoing a rapid range expansion northward and now breed throughout the Southeastern United States. As a facultative cavity-nesting species, they have the potential to compete with Wood Ducks (<em>Aix sponsa</em>) and Hooded Mergansers (<em>Lophodytes cucullatus</em>) for nest sites. Little is known about Whistling-Duck breeding biology, and estimates of clutch characteristics and rates of conspecific and interspecific brood parasitism (CBP and IBP, respectively) are lacking. We monitored Whistling-Duck nests in Louisiana to describe nesting chronology, clutch size of parasitized and unparasitized (normal) nests, and hatchability (i.e., the portion of eggs that hatched) for clutches of different sizes and types. We monitored a total of 558 nest boxes between 2020–2021 and determined the presence of brood parasitism for 231 Whistling-Duck nests. CBP was detected in 73 (31.6%) nests, and IBP was observed in 51 (22.1%) nests parasitized by Wood Ducks, two (0.9%) nests parasitized by Hooded Mergansers, and one nest contained eggs from all three species. Normal clutches were smaller (15.4 ± 4.4 eggs) than CBP clutches (26.1 ± 8.8 eggs) and mixed clutches (22.2 ± 5.3 eggs; clutches containing Wood Duck or Hooded Merganser eggs; all pairwise P < 0.0001). However, within clutch repeatability, estimates for egg morphology data (i.e., length, width, and mass) were low (< 0.40) for normal clutches, suggesting CBP went undetected. Of 180 fated nests used to determine hatchability, 66 (36.7%) were successful, 49 (27.2%) were abandoned, 64 (35.6%) were depredated, and one (0.6%) was nonviable. Considering successful nests, hatchability was high for all clutch size bins ranging from 67.4% (41–45 eggs) to 81.6% (11–15 eggs). Our study is the first to document Whistling-Ducks successfully hatching mixed-species broods, and such high productivity could be contributing to Whistling-Duck range expansion.

New cases of facultative interspecific brood parasitism in Black-winged Stilt (Himantopus himantopus) and Eurasian Coot (Fulica atra)

Abstract Many hypotheses try to explain the evolution and possible relations between obligate and facultative brood parasitism in birds. To explore this, a large number of observations and data are needed. Our understanding based on the observations of facultative parasitic species published in the literature is less clear compared to the obligate parasitic species. This communication is about three cases of facultative interspecific brood parasitism. Two nests of Black-headed Gull (Chroicocephalus ridibundus) parasite by Eurasian Coot (Fulica atra) and one nest of Pied Avocet (Recurvirostra avosetta) parasite by Black-winged Stilt (Himantopus himantopus). These observations are significant as long as interspecific brood parasitism was frequently described in Gruiformes (Rallidae) but has rarely observed within Charadriiformes.

Sex differences in the use of spatial cues in two avian brood parasites.

Shiny and screaming cowbirds are avian interspecific brood parasites that locate and prospect host nests in daylight and return from one to several days later to lay an egg during the pre-dawn twilight. Thus, during nest location and prospecting, both location information and visual features are available, but the latter become less salient in the low-light conditions when the nests are visited for laying. This raises the question of how these different sources of information interact, and whether this reflects different behavioural specializations across sexes. Differences are expected, because in shiny cowbirds, females act alone, but in screaming cowbirds, both sexes make exploratory and laying nest visits together. We trained females and males of shiny and screaming cowbird to locate a food source signalled by both colour and position (cues associated), and evaluated performance after displacing the colour cue to make it misleading (cues dissociated). There were no sex or species differences in acquisition performance while the cues were associated. When the colour cue was relocated, individuals of both sexes and species located the food source making fewer visits to non-baited wells than expected by chance, indicating that they all retained the position as an informative cue. In this phase, however, shiny cowbird females, but not screaming, outperformed conspecific males, visiting fewer non-baited wells before finding the food location and making straighter paths in the search. These results are consistent with a greater reliance on spatial memory, as expected from the shiny cowbird female's specialization on nest location behaviour.

Egg recognition and brain size in a cuckoo host

The evolution of animal brain size and cognitive ability is a topic of central significance in evolutionary ecology. Interspecific brood parasitism imposes severe selection pressures on hosts favoring the evolution of cuckoo egg recognition and rejection. However, recognizing and rejecting foreign parasitic eggs are enormous cognitive challenges for cuckoo hosts, which might select for an increase in brain size in birds with this capacity. To explore the association between cuckoo parasitism and the evolution of brain size in cinereous tits (Parus cinereus), we used two types of experimental parasitic eggs, real mimetic white-rumped munia (Lonchura striata) eggs and non-mimetic blue model eggs, to test the egg recognition ability of female cinereous tits, thereby comparing brain size variation among individuals that were able to recognize foreign eggs and those that lacked this ability. Interestingly, our results however did not support the prediction that cuckoo parasitism selects for an increase in brain size of host birds, since brain size of egg rejecters was not significantly larger than that of accepters. Hence, this study suggested that the evolution of cognitive ability did not allow recognition of foreign eggs by female cinereous tits. That was the case despite the evolution of a larger brain may have allowed for a reduction in the cost of brood parasitism by cuckoos.

Eastern Bluebirds (Sialia sialis) use color patterning, but not the colors themselves, as a cue to eject interspecific parasitic eggs

Abstract Brood parasitism results in substantial costs to hosts, yet not all species eject foreign eggs. Because the costs of mistakenly ejecting one’s own eggs are high, selection may favor ejection behavior only if it is unlikely a host will incorrectly eject her own eggs. Eastern Bluebirds (Sialia sialis) are currently subject to relatively low levels of interspecific brood parasitism but still sometimes eject parasitic eggs. Therefore, we tested which visual cues they use to eject foreign eggs with the prediction that only the most dissimilar eggs would be ejected, reducing the likelihood of a female making a mistake. House Sparrows (Passer domesticus), which occasionally parasitize bluebirds, lay eggs that have an off-white ground color with brown speckling. Therefore, to test which colors or patterns allow for discrimination of parasitic eggs, we generated 3-dimensional (3D)-printed model House Sparrow eggs and painted them entirely off-white, entirely brown, half off-white and half brown, or off-white with brown speckling. We then sequentially placed these 4 different model eggs in the nests of Eastern Bluebirds, with each nest receiving all treatments over the course of 4 days. After watching females enter and leave the nest box just one time after placement of the model egg, we found that speckled eggs were ejected half the time (7 of 14 nests), while no other treatment was ejected more than 3 times. Thus, Eastern Bluebird females eject eggs based primarily on color patterning (i.e. a speckled pattern) rather than coloration per se, and that they can do so quickly, as the average female had removed the model egg within 6 min of entering the nest. Because Eastern Bluebirds do not lay speckled eggs, but some brood parasites do (e.g., House Sparrows, Brown-headed Cowbirds [Molothrus ater]), selection may specifically favor ejection of eggs with a speckled pattern, not just eggs that have within-egg color contrasts.

Facultative brood parasitism by an American Robin (Turdus migratorius) in the nest of a Gray Catbird (Dumetella carolinensis)

Avian brood parasites can be classified as either obligate or facultative. Obligate brood parasites, such as Brown-headed Cowbirds (Molothrus ater), must lay their eggs in the nests of other species because they exhibit no parental care. Although facultative brood parasitism, when species that would normally lay eggs in their own nests dump eggs in the nest of another individual, may occur frequently among conspecifics, facultative interspecific brood parasitism is relatively rare. Here I report on observations made during the breeding season of 2018 of an example of facultative brood parasitism by an American Robin (Turdus migratorius) in the nest of a Gray Catbird (Dumetella carolinensis). Two robin eggs were laid in the nest of the catbird and were successfully raised by the catbird to fledging age. Although the young of obligate brood parasitic cowbirds are rarely raised successfully by catbirds, this is the first documented example, of which I am aware, of a Gray Catbird successfully raising the young of a facultative brood parasite.

Female and male rufous horneros eject shiny cowbird eggs using a mental template of the size of their own eggs

Hosts of interspecific brood parasites often evolve antiparasitic defences, like the recognition and rejection of parasite's eggs. Most hosts use differences in coloration and maculation to discriminate between their own and parasitic eggs, but there are a few cases of hosts using the size of eggs as a cue. To recognize parasite eggs, hosts may require the presence of their own eggs and use a discordancy rule or may use a mental template of their own eggs. Females are responsible for egg rejection in hosts in which they incubate alone, but if incubation is shared, males can also reject parasitic eggs. The rufous hornero, Furnarius rufus, a host of the shiny cowbird Molothrus bonariensis, ejects parasite eggs using egg size as a cue. We studied the cognitive mechanism underlying the recognition and ejection of parasitic eggs by this host. We experimentally parasitized hornero nests with eggs of different size, with and without the presence of host eggs and determined which sex was responsible for the ejection. We found that horneros ejected parasitic eggs using the size of the egg as a cue and did not need to compare parasitic eggs with their own eggs, which is consistent with the hypothesis of a mental template. Females and males ejected eggs at similar frequencies. We also found that cowbird eggs laid in hornero nests were longer and wider than those laid in nests of other host in the same area, which is consistent with the hypothesis of host-specific female cowbird lineages evolving larger eggs to deceit horneros from recognizing and ejecting their eggs.

Brood parasitism of an open-water spawning cichlid by the cuckoo catfish.

The cuckoo catfish Synodontis multipunctatus and S. grandiops are endemic to Lake Tanganyika and the only known nonavian vertebrates that exhibit obligate interspecific brood parasitism. Seven maternal mouth-brooding cichlid fish species are reported to be natural hosts of the parasitic catfish and share a common reproductive behaviour that the catfish exploits: cichlid females spawn eggs on the bottom, allowing the catfish female to place her eggs near the cichlid eggs, and the cichlid females collect the catfish eggs by mouth together with their own eggs. However, so far it has not been reported that the cuckoo catfish exploit different spawning behaviours. The genus Cyprichromis consists of five maternal mouth-brooding species endemic to Lake Tanganyika, most of which spawn and collect eggs in open water. This study reports that the cuckoo catfish also parasitizes the open-water spawning Cyprichromis coloratus, although it may not be a regular host.

Phylogenetic signal in the skull of cowbirds (Icteridae) assessed by multivariate and cladistic approaches

Closely related species are expected to resemble each other because of inheritance of features from their common ancestors, which are therefore said to carry phylogenetic signal. Cowbirds (Molothrus) are icterids well known from being interspecific brood parasites, but their taxonomy and evolutionary relationships have varied considerably based on morphology alone. In turn, these relationships became unsupported by molecular phylogenies, lending lower value to morphological data in general. However, the osteology of cowbirds has not yet been studied under a quantitative phylogenetic framework and it is uncertain whether their skulls carry phylogenetic signal. In order to test this, we assembled a data matrix, including continuous and discrete characters of the skull of cowbirds and allies, and analyzed it with two complementary approaches under the evolutionary framework provided by molecular phylogenies. We first took a multivariate approach, exploring the occupation of a phylomorphospace based on skull data and estimating the amount and significance of phylogenetic signal by calculation of the Kmult statistic. The second approach relied on a Maximum Parsimony optimization of characters on a scaffold tree. Our results indicate that, although some homoplasy exists, the skull of cowbirds and allies carries significant phylogenetic signal and provides useful characters to diagnose Molothrus and other still poorly diagnosed clades. This first comparative approach is promising and opens the possibility of integrating data from fossils, while encouraging further osteological analyses in cowbirds and other icterids.

Cases of occasional interspecific brood parasitism and egg dumping in Hungary

Abstract There are numerous publications in the ornithological literature on mixed-species broods, i.e. on cases when a species lays some or all of its eggs into the nests of other species. This phenomenon, known as brood parasitism, has not yet been studied in Hungary. Here, I use the term brood parasitism, but I could not separate cases of egg dumping, a reproductive error by females. Based on literature and my own observations, I found evidence for interspecific brood parasitism in 28 species breeding in Hungary, not including the cases of the obligate interspecific brood parasite, the Common Cuckoo (Cuculus canorus). Only one of these belongs to passerines, while in the rest of the cases, this phenomenon occurred in representatives of non-passerine families. However, cases of brood parasitism and nest parasitism have to be treated separately. The latter refers to cases when a species occupies a nest, usually a nesthole or nestbox, already containing eggs of another species, and lays its own eggs next to the foreign eggs. The present study provides data on European Roller (Coracias garrulus), Northern Goshawk (Accipiter gentilis), Common Kestrel (Falco tinnunculus), Red-footed Falcon (Falco vespertinus), Eurasian Hobby (Falco subbuteo), tit species (Parus, Cyanistes, Poecile spp.), Eurasian Nuthatch (Sitta europaea) and Eurasian Tree Sparrow (Passer montanus), but in all likelihood the number of species involved is much higher.

Nest defense and egg recognition in the grey-backed thrush (Turdus hortulorum): defense against interspecific or conspecific brood parasitism?

Cuckoos (Cuculus spp.) parasitize the nest of many host birds; however, it is not clear why some potential hosts that occupy the same area as cuckoos are rarely or not used as hosts. Potential hosts might adopt a variety of strategies to defend against cuckoo parasitism, such as attacking adult cuckoos to keep them away from the nest, rejecting cuckoo eggs, or recognizing and refusing to feed cuckoo nestlings. We investigated the strategies used by grey-backed thrushes (Turdus hortulorum), a potential host of cuckoos, to prevent cuckoo or conspecific brood parasitism. Our results indicated that the attack rate of grey-backed thrushes on cuckoo dummies was very low (11.4%). Thrushes showed egg polymorphism and exhibited 100% rejection of non-artificial blue model eggs. Thrushes also failed to identify the eggs (8.3% of rejection) of conspecifics. Thus, grey-backed thrushes show a high egg rejection towards nonmimetic eggs, but low towards conspecific eggs. We suggest that egg recognition and rejection in grey-backed thrushes may be a strategy to cope with interspecific brood parasitism rather than conspecific brood parasitism, and have probably evolved due to previous cuckoo parasitism. The explanations for high egg rejection in thrush (Turdus spp.) hosts were mixed without consistent conclusions. This study showed that grey-backed thrushes (Turdus hortulorum) show a high egg rejection towards nonmimetic eggs, but low towards conspecific eggs, suggesting that egg recognition and rejection in grey-backed thrushes may be a strategy to cope with interspecific brood parasitism rather than conspecific brood parasitism.

Alloparental care in the sea: Brood parasitism and adoption within and between two species of coral reef Altrichthys damselfish?

The evolution of parental care opens the door for the evolution of brood parasitic strategies that allow individuals to gain the benefits of parental care without paying the costs. Here we provide the first documentation for alloparental care in coral reef fish and we discuss why these patterns may reflect conspecific and interspecific brood parasitism. Species-specific barcodes revealed the existence of low levels (3.5% of all offspring) of mixed interspecific broods, mostly juvenile Amblyglyphidodon batunai and Pomacentrus smithi damselfish in Altrichthys broods. A separate analysis of conspecific parentage based on microsatellite markers revealed that mixed parentage broods are common in both species, and the genetic patterns are consistent with two different modes of conspecific brood parasitism, although further studies are required to determine the specific mechanisms responsible for these mixed parentage broods. While many broods had offspring from multiple parasites, in many cases a given brood contained only a single foreign offspring, perhaps a consequence of the movement of lone juveniles between nests. In other cases, broods contained large numbers of putative parasitic offspring from the same parents and we propose that these are more likely to be cases where parasitic adults laid a large number of eggs in the host nest than the result of movements of large numbers of offspring from a single brood after hatching. The evidence that these genetic patterns reflect adaptive brood parasitism, as well as possible costs and benefits of parasitism to hosts and parasites, are discussed.

Egg recognition and chick discrimination in colonial breeding birds

Theory predicts that parents will not raise unrelated offsprings. For colonial breeding birds, evolving an ability to recognize their own eggs and chicks can prevent misdirecting parental behaviour. To verify this hypothesis, egg recognition experiments were performed on colonial breeding Chinese pond herons (Ardeola bacchus) and cattle egrets (Bubulcus ibis) in Chengmai and Lingao, tropical Hainan Island, China. Furthermore, a chick discrimination experiment was conducted on Chinese pond herons. In our study area, we did not record conspecific or interspecific brood parasitism in the two heron species. The results showed that Chinese pond herons had similar recognition rates for the four types of experimental eggs and lacked recognition ability. Cattle egrets had variable abilities to recognize different types of foreign eggs and have low egg recognition ability. Chinese pond herons cannot discriminate foreign chicks. Therefore, we suggest that the two species of colonial breeding herons may lack or have low egg recognition ability, and Chinese pond herons show no nestling recognition ability.

Coevolutionary arms race between a specialist brood parasite, the Screaming Cowbird, and its host, the Grayish Baywing

Interspecific brood parasites exploit the parental care of host species. This exploitation entails fitness costs for the hosts, which favor the evolution of antiparasitic defenses. Host defenses select for counter-defenses in the parasite, which in turn select for improved host defenses; this results in a coevolutionary arms race that may operate at each stage of the nesting cycle of the host. Most studied examples of the coevolutionary arms race in brood parasites are restricted to the egg stage, with relatively few studies showing coevolution between hosts and parasites at the nestling or fledgling stages; studies on the whole set of host defenses and potential parasite counter-defenses at each stage of the breeding cycle are still lacking. Systems in which parasites are host specialists are particularly well suited to an examination of the pairwise coevolutionary interactions before, during and after host egg-laying, and how these interactions have shaped host resistance or tolerance of parasitism. The Screaming Cowbird (Molothrus rufoaxillaris) is one of the most specialized brood parasites, and mainly parasitizes nests of a single host species, the Grayish Baywing (Agelaioides badius). Parasitism rates of Grayish Baywing nests are extremely high, with most nests parasitized several times. Several traits of this host-parasite system suggest ancient coevolutionary relationships encompassing the entire nesting cycle. In this paper we summarize the main results of a long-term study on the costs of Screaming Cowbird parasitism on the Grayish Baywing’s reproductive success and how these costs have favored reciprocal adaptations and counter-adaptations at each stage of the nesting cycle.