Brood Parasitism Research Articles

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.

Instances of intraspecific nest parasitism in eastern and Rio Grande wild turkeys

AbstractNest parasitism can play an important role in processes regulating population dynamics of both hosts and parasites. Inter‐ and intra‐specific nest parasitism are 2 alternative reproductive strategies observed to occur in about 1% of all bird species. Recently, low productivity in wild turkey (Meleagris gallopavo) populations has resulted in population declines across the southeastern United States. Reproductive output may be influenced by nest parasitism, but the extent of nest parasitism and how it may be related to productivity of wild turkey populations are poorly understood. Herein, we illustrate 6 unreported examples of intraspecific nest parasitism obtained using GPS telemetry data from female wild turkeys in Georgia and Louisiana during 2014−2018. Further, we report 3 occurrences of nest parasitism in Texas using photographic evidence. Our findings suggest that ≥6% of nests are potentially parasitized, and that multiple females may visit and parasitize a single nest. Given recent declines in reproductive output of wild turkeys throughout the southeastern United States, we encourage researchers to continue assessing potential for nest parasitism across wild turkey populations and how this potential may be influenced by predator abundance and activity.

A review on brood parasitism in Passeriformes, with an emphasis on Asian Koel (Eudynamys scolopacea) and House crow (Corvus splendens) in Pakistan Forest Institute Peshawar, Khyber Pakhtunkhwa

A review on brood parasitism in Passeriformes, with an emphasis on Asian Koel (Eudynamys scolopacea) and House crow (Corvus splendens) in Pakistan Forest Institute Peshawar, Khyber Pakhtunkhwa

Effects of nest-box environment on fledgling success rate and pathogen load.

Nest boxes have been used for many decades as tools for conservation and to study avian population dynamics. Plastic is increasingly used as a material for nest boxes, but no studies have investigated effects of this different material. Two consecutive studies were conducted to investigate effects of nest-box environment on nidicolous parasites, bacteria and fungi, as well as nest success, in blue tits Cyanistes caeruleus and great tits Parus major. The first compared microclimate and parasite and pathogen load in plastic and wooden nest boxes. The second tested the nest protection hypothesis – that birds naturally incorporate aromatic herbs into nests to decrease nest parasites and pathogens – by comparing parasite and pathogen load in plastic nest boxes to which aromatic or non-aromatic plant material was added. No significant difference in nest-box temperature or relative humidity was found between plastic and wooden boxes. Wooden boxes, however, contained 30-fold higher numbers of fleas and a higher total bacterial load on chicks. Fledging success for blue tit broods was significantly higher in wooden boxes. Parasites and bacteria did not decrease by the inclusion of aromatic herbs. The results increase the evidence base for nest-box design in support of plastic, which can provide an appropriate alternative nest-box material to wood, with apparently no difference in microclimate and no increase in the load of measured parasites and pathogens.

A novel function of egg burial: burying material prevents eggs rolling out of wind-swayed nests

Egg burial behaviour, that is, when parents bury the eggs with a layer of nest material during the egg-laying stage, has been described in various egg-laying animals. Several functions of egg burial have been described in animals with different life histories and breeding traits, but rarely reveal distinctive functions between sister species. In the polygamous Eurasian penduline tit, Remiz pendulinus , sexual conflict over care has been proposed to drive egg burial since, during egg laying, females hide eggs from males to prevent them abandoning the nest. Females then have the option to desert the clutch themselves and leave parenting to the male. However, in a congeneric species, the Chinese penduline tit, Remiz consobrinus , males have been seen with females in the nest at night, which indicates males know of the eggs’ existence. In this study, we investigated egg burial function in Chinese penduline tits and experimentally tested four hypothesized functions of egg-burying behaviour. (1) We found that egg burial is unlikely to play a role in sexual conflict resolution, as both males and females appeared to bury eggs during egg laying and both freely entered and roosted in the nests with eggs exposed at night. (2) Egg burial does not prevent nest parasitism, as no egg rejection or clutch abandonment was observed in clutches with model parasitic eggs. (3) Our results do not support the temperature regulation hypothesis since the temperature difference between buried and experimentally unburied eggs did not affect hatching success. (4) Notably, our results support the novel egg protection against wind hypothesis since the burying layer efficiently prevented the eggs from rolling out of wind-swayed nests. The difference our study found between the two Remiz species highlights that one behaviour, egg burial, can serve different evolutionary functions between closely related species. • We experimentally tested four functions of egg burial in wild Remiz consobrinus . • Egg burial did not function against brood parasitism or in resolving sexual conflict. • Burying layer regulates egg temperature, but this did not improve hatching success. • Burying material efficiently stops eggs from being blown out of wind-swayed nest. • One behaviour can fulfil different functions even in closely related species.

Egg rejection based on egg size recognition as a specific strategy against parasitic cuckoos.

In the coevolutionary interactions between avian brood parasites and their hosts, egg recognition based on color and/or pattern is a common and effective defense to counter parasitism. However, for egg recognition based on size, only a few studies have found affirmative results, and they do not provide unambiguous evidence that egg size recognition in hosts has evolved as an important and specific anti-parasite adaptation against parasite eggs. We studied the brood parasite system between the Asian emerald cuckoo Chrysococcyx maculatus and its host, the chestnut-crowned warbler Phylloscopus castaniceps. The cuckoo parasitizes the warbler using non-mimetic and larger eggs at a parasitism rate of 12.9%. The warbler nests used in this experiment were built in a dark environment with the nest illuminance near 0 lux. Experiments with 2 types of model eggs with colors and patterns resembling cuckoo eggs of different sizes (cuckoo egg size or host egg size) showed that the warblers were able to reject 63.6% of cuckoo model eggs under these dim light conditions. However, model eggs with the same color and pattern similar to the warbler egg size were always accepted. This study provides strong evidence supporting the theory that egg size recognition can be evolved in hosts as a specific anti-parasite adaptation against cuckoos. We suggest that the egg size recognition of the warbler is an outcome of the tradeoff between the costs of violating the parental investment rule and suffering cuckoo parasitism.

Nest site selection and breeding ecology of the red-billed blue magpie Urocissa erythrorhyncha in central China

Abstract While knowledge on birds’ breeding ecology is essential for understanding avian adaptation and managing conservation, it is poorly studied for many species, even for some common species. The knowledge of the natural history of the red-billed blue magpie (Urocissa erythrorhyncha), a species widely distributed in China and Southeast Asia, is sketchy. Here we present detailed data of nest site selection and the breeding ecology of red-billed blue magpie in central China, and of the effects of nest predation and brood parasitism on reproductive strategies. Most nests were built on Phyllostachys sulphurea and Quercus acutissima. Breeding season ranged from March to August. The first egg was laid between early April and late July. The incubation period lasted 15 days and the nestling period, 18 days. Average clutch size was 4.6 eggs, and brood size at fledging was 3.3 young. Overall, 43.8% of nesting attempts successfully produced at least one fledged young. Nest predation and brood parasitism were the two main reasons for fledging failure, which mainly occurred after April. Correspondingly, U. erythrorhyncha showed a tendency to build nests higher up and have a smaller clutch size in late stages of the breeding season. This study provides the first reliable and comprehensive information on the reproductive parameters of U. erythrorhyncha, which will lay a foundation for further understanding this species’ biology and opens up an avenue for large-scale comparative studies of the Urocissa genus or higher-level taxa.

Complete mitogenome of the Common Koel Eudynamys scolopaceus Linnaeus 1758 (Aves: Cuculidae)

The Common Koel Eudynamys scolopaceus Linnaeus 1758, belongs to the family Cuculidae and order Cuculiformes. This omnivorous bird exhibits obligate nest parasitism. Here, the complete mitogenome of E. scolopaceus was determined and phylogenetically compared with those of other Cuculidae species. The newly sequenced complete mitogenome was a circular DNA molecule with a size of 17,610 bp (OM115963). This mitogenome had a higher A + T content (57.58%) than G + C content (42.42%). Phylogenetic analysis revealed that E. scolopaceus was most closely related to Eudynamys taitensis and the genus Cuculus, providing useful molecular information for further research on the phylogeny of the family Cuculidae.

A review of the cues used for rejecting foreign eggs from the nest by the Eurasian blackbird (Turdus merula).

Avian brood parasitism is reproductively costly for hosts and selects for cognitive features enabling anti‐parasitic resistance at multiple stages of the host's breeding cycle. The true thrushes (genus Turdus) represent a nearly worldwide clade of potential hosts of brood parasitism by Cuculus cuckoos in Eurasia and Africa and Molothrus cowbirds in the Americas. The Eurasian blackbird (Turdus merula) builds an open‐cup nest and is common within much of the common cuckoo's (C. canorus) breeding range. While this thrush is known to be parasitized at most only at low rates by this cuckoo, the species is also a strong rejector of nonmimetic foreign eggs in the nest. Given their open‐cup nesting habits, we predict that Eurasian blackbirds primarily use visual cues in making a distinction between own and parasitically or experimentally inserted foreign eggs in the nest. We then provide a comprehensive and quantitative review of the literature on blackbird egg rejection studies. This review corroborates that vision is the primary sensory modality used by blackbirds in assessing eggs, but also brings attention to some other, less commonly studied cues which appear to influence rejection, including predator exposure, individual experience, stage of clutch completion, and maternal hormonal state. Blackbirds are also able to recognize and eject even highly mimetic eggs (including those of conspecifics) at a moderate rate, apparently relying on many of the same sensory cues. Although the cues involved in foreign egg recognition by Eurasian blackbirds do not appear specialized to nonmimetic cuckoo parasitism, we cannot differentiate between the possibility of egg rejection being selected by mostly conspecific parasitism or by the evolutionary ghost of a now‐extinct, mimetic cuckoo host‐race.

Opportunity is not everything: genetic monogamy and limited brood parasitism in a colonial woodpecker

Opportunity is not everything: genetic monogamy and limited brood parasitism in a colonial woodpecker

Nest, eggs, and nestlings of the Gray-headed Tanager (Eucometis penicillata albicollis) from São Paulo State, Brazil

The Gray-headed Tanager (Eucometis penicillata) has 7 subspecies widely distributed in Central and South America. Scattered reproductive data are available for most of them, but reproductive aspects were thoroughly documented only for E. p. stictothorax, from Costa Rica. Here, we provide detailed descriptions of nests, eggs, and nestlings of E. p. albicollis from southeastern Brazil, and compile nesting information available from this and other subspecies from the literature. During the 2019–2020 and 2020–2021 breeding seasons, we found 4 nests that were active from October to January. Nests were deep cups with 8.5–11.1 cm in outer diameter, constructed of loosely attached dry fibers and sticks, and could be supported at their rims, laterally, or from beneath. They were built in riparian forest understory, 1.1–1.5 m above ground, 1.0–10.5 m away from forest streams, and 72–100 m from the forest edge. Clutches consisted of 3 eggs. Eggs were brownish-gray in background color, with dark-brown blotches, measured 21.9 mm (±0.8) in length and 16.2 mm (±0.7) in width, and weighed 3.0 g (±0.3). The hatchlings had reddish skin, bright orange mouth lining, and white commissure. The pair shared nestling provisioning and we also document the first case of brood parasitism by Shiny Cowbird (Molothrus bonariensis) for the Gray-headed Tanager. Upon comparing our data with that of other subspecies, we observed differences in nest material, breeding phenology, clutch size, and eggs and nestling characteristics, which could be attributed to local adaptations of geographically distinct subspecies or to phylogenetic divergences between still unsplit species.

Should I stay or should I go: the effect of avian brood parasitism on host fledging dynamics

Should I stay or should I go: the effect of avian brood parasitism on host fledging dynamics

The location of thrush nests on buildings affects the chance of cowbird parasitism

Nest site placement is a critical choice among passerines, being an important factor that affects their breeding success. In urban areas, human buildings offer suitable nesting sites usually less exposed to predators and brood parasitic birds and readily available to be reused for several breeding seasons. However, the extent to which the features of nest placement sites in buildings contribute to reduce nest detectability by predators and brood parasites is still unknown. Here, we tested whether the features of the nesting site (i.e., lateral concealment, distance to the building ceiling, and height above ground) affect the chance of brood parasitism by Shiny Cowbirds (Molothrus bonariensis) in Pale-breasted Thrushes (Turdus leucomelas) nests placed on buildings in a Brazilian suburban area from 2013 to 2019. Cowbird parasitism increased throughout the study years, and nests closer to ceilings, supposedly better concealed, were more likely to be parasitized. Laying date, height above ground, and lateral concealment were not related to the probability of cowbird parasitism. We suggest that less concealed nests enhance vicinity monitoring by parents, allowing a faster agonistic response to the presence of cowbirds near the nest. Our results indicate that nest site location in cities may have consequences for the breeding success of cowbird hosts.

Genetic architecture facilitates then constrains adaptation in a host–parasite coevolutionary arms race

In coevolutionary arms races, interacting species impose selection on each other, generating reciprocal adaptations and counter adaptations. This process is typically enhanced by genetic recombination and heterozygosity, but these sources of evolutionary novelty may be secondarily lost when uniparental inheritance evolves to ensure the integrity of sex-linked adaptations. We demonstrate that host-specific egg mimicry in the African cuckoo finch Anomalospiza imberbis is maternally inherited, confirming the validity of an almost century-old hypothesis. We further show that maternal inheritance not only underpins the mimicry of different host species but also additional mimetic diversification that approximates the range of polymorphic egg “signatures” that have evolved within host species as an escalated defense against parasitism. Thus, maternal inheritance has enabled the evolution and maintenance of nested levels of mimetic specialization in a single parasitic species. However, maternal inheritance and the lack of sexual recombination likely disadvantage cuckoo finches by stifling further adaptation in the ongoing arms races with their individual hosts, which we show have retained biparental inheritance of egg phenotypes. The inability to generate novel genetic combinations likely prevents cuckoo finches from mimicking certain host phenotypes that are currently favored by selection (e.g., the olive-green colored eggs laid by some tawny-flanked prinia, Prinia subflava, females). This illustrates an important cost of coding coevolved adaptations on the nonrecombining sex chromosome, which may impede further coevolutionary change by effectively reversing the advantages of sexual reproduction in antagonistic coevolution proposed by the Red Queen hypothesis.

Host community-wide patterns of post-fledging behavior and survival of obligate brood parasitic brown-headed cowbirds.

The antagonistic arms races between obligate brood parasites and their hosts provide critical insights into coevolutionary processes and constraints on the evolution of life history strategies. In avian brood parasites-a model system for examining host-parasite dynamics-research has primarily focused on the egg and nestling stage, while far less is known about the behavior and ecology of fledgling and juvenile brood parasites. To provide greater insights into the post-fledging period of generalist brood parasites, we used handheld and automated telemetry systems to examine the behavior and survival of fledgling brown-headed cowbirds (Molothrus ater). Our host community-wide analysis (data on cowbirds fledged from different host species were pooled) shows that fledgling cowbirds' follow patterns of movement and survival found across the post-fledging literature on parental passerine species. Cowbird fledgling survival was lowest during the first 3days post-fledging, whereas daily rates of survival neared 100% after about 16days post-fledging. Cowbird daytime post-fledging activity rates, perch heights, and distance from the natal area all increased with fledging age and young generally gained independence from host parents at 3-4weeks post-fledging, with approximately the same latency as has been observed in studies on fledglings of cowbird host species. Our research demonstrates how automated telemetry systems can overcome past methodological limitations in post-fledging research and provides an important foundation for future studies examining adaptations that cowbirds and other brood parasites use to exploit hosts during the post-fledging period.

Individual experience as a key to success for the cuckoo catfish brood parasitism

Brood parasites are involved in coevolutionary arms races with their hosts, whereby adaptations of one partner elicit the rapid evolution of counter-adaptations in the other partner. Hosts can also mitigate fitness costs of brood parasitism by learning from individual or social experience. In brood parasites, however, the role of learning can be obscured by their stealthy behaviour. Cuckoo catfish (Synodontis multipunctatus) parasitise clutches of mouthbrooding cichlids in Lake Tanganyika and are the only non-avian obligate brood parasites among vertebrates. We experimentally demonstrate that cuckoo catfish greatly enhance their efficiency in parasitising their hosts as they learn to overcome host defences. With increasing experience, cuckoo catfish increased their parasitism success by greater efficiency through improved timing and coordination of intrusions of host spawnings. Hence, within the coevolutionary arms races, brood parasites learn to overcome host defences during their lifetime.

Common Cuckoo Nestling Adapts Its Begging Behavior to the Alarm Signaling System of a Host

Cuckoo nestlings thrive as avian brood parasites. To acquire sufficient food from the host parents, cuckoo nestlings generally make louder begging calls than host nestlings, but this may cause them to be more likely to attract the attention of predators. Studies have shown that nestlings would respond to the alarm calls of their parents by begging less, or crouching and remaining silent as an adaptation to reduce the risk of being heard by predators. Nevertheless, research is lacking on how parasite nestlings respond to alarm calls of their host parents. We studied the common cuckoo (Cuculus canorus) and one of the most common cuckoo host species, the oriental reed warbler (Acrocephalus orientalis), using a playback experiment in Yongnianwa National Wetland Park during the breeding seasons from June to July, 2020–2021. The begging behaviors of either cuckoo or host nestlings were quantified by playing back the alarm calls of host adults toward common cuckoo, sparrowhawk (Accipiter nisus), or oriental turtle doves (Streptopelia orientalis). Meanwhile, normal begging without playback, playback of the natural singing (NS) of host adults, and background noise (BN) were included as behavioral reference, non-threatening comparison, and playback control, respectively. The results showed that the cuckoo and host nestlings produced similar levels of begging with or without playback of NS and BN; however, both types of nestlings inhibited their begging intensity after hearing the playback of alarm calls, although they did not respond differently to the various alarm call playbacks. This study therefore elucidated that coevolution has selected the common cuckoo nestlings that adapt their begging behavior to the parent–offspring communication of alarm signaling in their host, oriental reed warblers.

Host parent responses to heterospecific parasite nestling alarm calls are independent of past and current experience with experimental brood parasitism

Communication between parents and dependent offspring is critical not only during provisioning, but also in antipredator contexts. In altricial birds, a top cause of reproductive failure is nest predation, and alarm calls both by parents and chicks can serve to alert others and increase the likelihood of offspring escaping predation. Understanding the factors that determine the strength of parental antipredator responses to different nestling alarm calls can provide insight into parent-offspring recognition. The prothonotary warbler (Protonotaria citrea), a host of the obligate brood parasite, the brown-headed cowbird (Molothrus ater), never rejects cowbird young and raises the parasite together with its own offspring. To determine whether warbler parents learn cowbird nestling alarm calls, we presented experimentally parasitized or non-parasitized parents with playbacks of conspecific warbler, parasitic cowbird, and a harmless heterospecific control, eastern bluebird (Sialis sialis), nestling alarm calls. We recorded the latency to respond and the number of chips given by members of the resident warbler pair. We found that parents were most likely to respond to warbler nestling alarm calls, least likely to respond to bluebird calls, with a statistically intermediate likelihood of responding to cowbird calls. Critically, current and past parasitism status did not affect the likelihood of response to any playback or the number of chips given, however, currently parasitized parents had greater response latencies to playbacks than non-parasitized parents. These results suggest that warbler parents do not learn cowbird alarm calls from breeding experiences and, in turn, that cowbirds may employ a generalized, bet-hedging alarm call.

Eggshell texture but not odor treatment affects model egg rejection in American robins (Turdus migratorius).

To curb fitness costs associated with obligate avian brood parasitism, some hosts have evolved to reject foreign eggs in the nest. American robins (Turdus migratorius) are among the few hosts of the brown-headed cowbird (Molothrus ater) that mostly remove parasitic eggs from their nests. With the parasite's eggs looking nothing like their own, American robins likely rely most on visual cues when making rejection decisions. However, we still know little about the roles thattactile and olfactory cues play in robin's or other rejecter hosts' rejection decisions. Here, we conducted a set of experiments to test for the use of tactile or olfactory cues in egg rejection by robins. For the tactile experiment, we found that robins were more likely to reject rough rather than smooth eggs. However, our tactile model egg design was not able to fully discriminate between tactile and visual sensorymodalities. In the olfaction experiment, we did not find a significant effect of egg scent treatment on rejection rates. Accordingly, future studies on egg rejection should attempt to fully distinguish between tactile and visual cues, as well as examine olfactory cues in other egg rejecter host species.

Defensive adaptations to cuckoo parasitism in the black-browed reed warbler (Acrocephalus bistrigiceps): recognition and mechanism.

Hosts of avian brood parasites suffer a high cost of reproductive loss due to parasitism, driving them to evolve a variety of anti-parasitic defenses. These defenses comprise a series of components, including the recognition of brood parasites and the eggs laid by the parasites, cues used for recognition, and the mechanisms on which these behaviors are based. In this study, we conducted egg recognition and nest intruder experiments to examine these components of anti-parasitic behavior in the black-browed reed warbler (Acrocephalus bistrigiceps), a rare host of the common cuckoo (Cuculus canorus). We found that the host possessed strong recognition capacity, rejecting 100% of parasitic eggs, and used a template-based mechanism for egg recognition. The host birds also rejected 80% of their own eggs on which artificial markings were added to the blunt pole; however, they accepted all eggs with the same manipulation on the sharp pole, implying that the blunt pole was an important recognition cue. Furthermore, the host exhibited stronger aggression to cuckoos than to harmless controls; a behavior specific to the incubation stage rather than the nestling stage. Therefore, the host was able to distinguish the cuckoo from other nest intruders as being a brood parasite. These results together help explain the near absence of cuckoo parasitism in black-browed reed warblers and provide new information concerning anti-parasitic defenses in this host species.