Brood Parasitism Research Articles

A bird's eye view of the hippocampus beyond space: Behavioral, neuroanatomical, and neuroendocrine perspectives

Although the hippocampus is one of the most-studied brain regions in mammals, research on the avian hippocampus has been more limited in scope. It is generally agreed that the hippocampus is an ancient feature of the amniote brain, and therefore homologous between the two lineages. Because birds and mammals are evolutionarily not very closely related, any shared anatomy is likely to be crucial for shared functions of their hippocampi. These functions, in turn, are likely to be essential if they have been conserved for over 300 million years. Therefore, research on the avian hippocampus can help us understand how this brain region evolved and how it has changed over evolutionary time. Further, there is a strong research foundation in birds on hippocampal-supported behaviors such as spatial navigation, food caching, and brood parasitism that scientists can build upon to better understand how hippocampal anatomy, network circuitry, endocrinology, and physiology can help control these behaviors. In this review, we summarize our current understanding of the avian hippocampus in spatial cognition as well as in regulating anxiety, approach-avoidance behavior, and stress responses. Although there are still some questions about the exact number of subdivisions in the avian hippocampus and how that might vary in different avian families, there is intriguing evidence that the avian hippocampus might have complementary functional profiles along the rostral-caudal axis similar to the dorsal-ventral axis of the rodent hippocampus, where the rostral/dorsal hippocampus is more involved in cognitive processes like spatial learning and the caudal/ventral hippocampus regulates emotional states, anxiety, and the stress response. Future research should focus on elucidating the cellular and molecular mechanisms – including endocrinological - in the avian hippocampus that underlie behaviors such as spatial navigation, spatial memory, and anxiety-related behaviors, and in so doing, resolve outstanding questions about avian hippocampal function and organization.

Hybrid Encryption based Access Control Approach for Securing Cloud Computing

Cloud computing has become an integral part of modern technological infrastructure, facilitating the storage and processing of vast amounts of data. However, ensuring the security of sensitive information in the cloud remains a persistent challenge. This paper proposes a novel approach to enhance the security of cloud computing through hybrid encryption, leveraging the Whale Optimization Algorithm (WOA) and Cuckoo Search Optimization (CSO) algorithms. Hybrid encryption, combining symmetric and asymmetric cryptographic techniques, is employed to address the limitations of traditional encryption methods in cloud environments. The Whale Optimization Algorithm and Cuckoo Search Optimization are utilized to optimize key generation and management processes, enhancing the overall efficiency and security of the encryption scheme. The Whale Optimization Algorithm, inspired by the social behavior of humpback whales, is employed to optimize the parameters of the encryption algorithm. WOA's exploration and exploitation capabilities are leveraged to find an optimal balance in the encryption process, improving the overall robustness against potential attacks. Complementing WOA, the Cuckoo Search Optimization algorithm is applied to optimize the key distribution and update mechanisms. Modeled after the brood parasitism behavior of cuckoo birds, CSO excels in searching large solution spaces, making it suitable for refining the distribution of encryption keys and ensuring their constant adaptability to dynamic cloud environments.

Breeding ecology of Eastern Crowned Leaf Warbler and brood parasitism by the Oriental Cuckoo

Breeding ecology of Eastern Crowned Leaf Warbler and brood parasitism by the Oriental Cuckoo

Chase-away evolution maintains imperfect mimicry in a brood parasite–host system despite rapid evolution of mimics

We studied a brood parasite–host system (the cuckoo finch Anomalospiza imberbis and its host, the tawny-flanked prinia Prinia subflava) to test (1) the fundamental hypothesis that deceptive mimics evolve to resemble models, selecting in turn for models to evolve away from mimics (‘chase-away evolution’) and (2) whether such reciprocal evolution maintains imperfect mimicry over time. Over only 50 years, parasites evolved towards hosts and hosts evolved away from parasites, resulting in no detectible increase in mimetic fidelity. Our results reflect rapid adaptive evolution in wild populations of models and mimics and show that chase-away evolution in models can counteract even rapid evolution of mimics, resulting in the persistence of imperfect mimicry.

Lack of host specialization despite selective host use in brood parasitic cuckoo catfish.

Host-parasite dynamics involve coevolutionary arms races, which may lead to host specialization and ensuing diversification. Our general understanding of the evolution of host specialization in brood parasites is compromised by a restricted focus on bird and insect lineages. The cuckoo catfish (Synodontis multipunctatus) is an obligate parasite of parental care of mouthbrooding cichlids in Lake Tanganyika. Given the ecological and taxonomic diversity of mouthbrooding cichlids in the lake, we hypothesized the existence of sympatric host-specific lineages in the cuckoo catfish. In a sample of 779 broods from 20 cichlid species, we found four species parasitized by cuckoo catfish (with prevalence of parasitism of 2%-18%). All parasitized cichlids were from the tribe Tropheini, maternal mouthbrooders that spawn over a substrate (rather than in open water). Phylogenetic analysis based on genomic (ddRAD sequencing) and mitochondrial (Dloop) data from cuckoo catfish embryos showed an absence of host-specific lineages. This was corroborated by analyses of genetic structure and co-ancestry matrix. Within host species, parasitism was not associated with any individual characteristic we recorded (parent size, water depth), but was costly as parasitized parents carried smaller clutches of their own offspring. We conclude that the cuckoo catfish is an intermediate generalist and discuss costs, benefits and constraints of host specialization in this species and brood parasites in general.

Nest desertion as an anti-parasitism strategy in hosts selects for late egg-laying behavior in cuckoos

Studies have shown that brood parasites lay their eggs early in the egg-laying sequence of their hosts, providing them with the advantage of earlier hatching. However, common cuckoos (Cuculus canorus) appear to parasitize the nests of gray bushchat (Saxicola ferreus) during the late egg-laying stage. The bushchat often abandons parasitized nests in the early stages, but not in the late egg-laying stages, thus favoring late egg-laying by cuckoos. In this study, four experiments were conducted to determine whether gray bushchats employ a nest desertion strategy targeted at cuckoo parasitism. The results showed that nest desertion was significantly correlated with parasitism cues and occurred mainly during the hosts' early egg-laying stage. Our study provides the first experimental evidence that nest desertion is an anti-parasitic strategy used by hosts in response to cuckoos. Additionally, our experiments demonstrated that the nest desertion is influenced by the trade-offs of investments in different egg-laying stages.

Shiny Cowbird (Molothrus bonariensis) brood parasitism occurrence and impact increases with decreasing forest cover

ABSTRACT Cowbirds brood parasitism has a detrimental effect on the breeding success of their hosts. The occurrence of parasitism observed may be related to environmental features at landscape or nest-site scales. Such relationships have been assessed for the Brown-headed Cowbird (Molothrus ater) in the large forests of the northern hemisphere. Here, we present a study conducted on the Shiny Cowbird (M. bonariensis) in native forests of the southern hemisphere in Argentina. These forests are characterised as semi-open woodlands, with forest fragments of variable sizes immersed in native grasslands. We aimed to evaluate the effect of Shiny Cowbird brood parasitism on the breeding success of a native passerine, the Masked Gnatcatcher (Polioptila dumicola), and to assess the relationship of its occurrence with environmental features at landscape and nest-site scales. During three breeding seasons (2015–2018) we monitored 207 gnatcatcher nests of which 70 were parasitised. Brood parasitism was the cause of nest failure in 60% of the parasitised nests. In addition, breeding success measured by apparent nest success, egg survival, hatching success and nestling survival were significantly lower for parasitised nests than for non-parasitised nests. Brood parasitism occurrence was negatively associated with forest cover, where nests located in sites with less forest cover experienced a higher occurrence of parasitism than those with greater cover. As these native semi-open forests face a continuous decline, our results add to the evidence of negative impacts of deforestation.

Brood parasitism and egg recognition in three bunting hosts of the cuckoos.

Comparative studies of egg recognition and rejection between various sympatric hosts provide insight into the coevolutionary history of the hosts and parasites, as well as the degree of antagonism between the species. Although buntings are widely considered to be a suitable host taxon for cuckoos, there has been relatively little research on this example of parasitism and host antiparasitic behaviour. Here we provided the first report on brood parasitism and egg recognition in three sympatric ground-nesting bunting hosts of the common cuckoo (Cuculus canorus), namely the yellow-throated bunting (Emberiza elegans), south rock bunting (E. yunnanensis), and crested bunting (E. lathami). The results show that for the five breeding seasons during 2018-2022, the parasitism rate by common cuckoos was 0.87% and 0.45% in yellow-throated buntings and south rock buntings, respectively, whereas the parasitism rate by an unidentified parasite was 4% during 2018-2023 in the crested bunting. The rejection rates of the three bunting hosts for blue non-mimetic eggs were 89.3%, 88.9%, and 100% for yellow-throated buntings, south rock buntings, and crested buntings, respectively. The rejection rates for red non-mimetic eggs by yellow-throated buntings and south rock buntings were lower at 76.9% and 82.4%, respectively. All three sympatric bunting hosts examined had high levels of egg recognition and egg rejection, suggesting that it may have been subjected to high parasitic history and that egg recognition ability was retained after the loss of parasitism, which needs to be further verified by future experiments.

Lack of evidence for chemical integration of the cuckoo-bee Stelis nasuta (Latreille, 1809) and Coelioxys aurolimbata (Förster, 1853) with their main host Megachile parietina (Geoffroy, 1785)

Megachileparietina is a solitary megachilid species, which sometimes nests in large aggregations. Such a condition attracts a diverse entomological fauna, including several parasites. Here, we focused on two cuckoo-bees of this species, Stelis nasuta and Coelioxys aurolimbata (Megachilidae) and investigated if chemical integration with the host favours their reproductive success. Lipids on the epicuticle and in the Dufour’s gland secretion, possibly contributing to protecting the eggs against dehydration, of the three species showed species-specific mixtures of long-chained linear alkanes and alkenes. Moreover, contrary to what has been reported for some cuckoo-bees of the genus Nomada, we found no evidence that the mandibular glands of parasite males contribute to female chemical mimicry. Therefore, we found no indication that chemical integration is part of the adaptive strategies of these two brood parasites.

Host learning selects for the coevolution of greater egg mimicry and narrower antiparasitic egg-rejection thresholds.

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 current experience with brood parasitism are more likely to reject foreign eggs. Here we confirm experimentally the role of prior experience in altering subsequent egg-rejection decisions in the American robin Turdus migratorius, a free-living host species of an obligate brood parasite, the brown-headed cowbird Molothrus ater. We then model the coevolutionary trajectory of both the extent of mimicry of host eggs by parasitic eggs and the host's egg rejection thresholds in response to an increasing role of learning in egg recognition. Critically, with more learning, we see the evolution of both narrower (more discriminating) rejection thresholds in hosts and greater egg mimicry in parasites. Increasing host clutch size (number of eggs/nest) and increasing parasite load (parasitism rate) also have narrowing effects on the egg-rejection threshold. Together, these results suggest that learning from prior experience with egg rejection may play an important role in the coevolution of egg-mimetic lineages of brood parasites and the refined egg rejection defenses of hosts.

Long-term decline in Brown-headed Cowbird (Molothrus ater) abundance has not led to less brood parasitism of four riparian songbird species

Long-term decline in Brown-headed Cowbird (Molothrus ater) abundance has not led to less brood parasitism of four riparian songbird species

Generalists and specialists of brood parasitism in spider wasps (Hymenoptera: Pompilidae)

ABSTRACT Based on emergence records from trap nests and naturally occurring nests, we determined the brood parasitism behaviour of Irenangelus punctipleuris (Pompilidae: Ceropalinae) for the first time and that of Dipogon (Nipponodipogon) nagasei (Pompilidae: Pepsinae) as a complement to a previous study. The former species was found to parasitise Auplopus carbonarius and A. pygialis (Pompilidae: Pepsinae), while the latter species was found to parasitise Di. (Deuteragenia) sperconsus (Pepsinae). When using the well-established system of categories of brood parasitism in Pompilidae, Irenangelus corresponds to type A brood parasitism (‘highwayman’) and Nipponodipogon corresponds to type B brood parasitism (‘sneak thief’). In comparison with brood parasitism in birds, we propose new concepts, namely ‘generalists’ and ‘specialists’ of brood parasitism, which correspond to type A and type B brood parasites, respectively. We discuss the differences in behavioural patterns and morphological features between the two types. We also confirm the proposed concepts by their molecular phylogenetic positions.

Restoring Nature's Song: How Habitat Restoration Benefits Avifauna

Habitat restoration has proved to be a vital strategy in combating the widespread biodiversity loss caused by habitat degradation across the globe. The key roles played by avian species in critical ecosystem functions such as pollination, seed dispersal, and decomposition have made them an integral part of ecosystems, making them vital to the restoration process. Their detectability and cost-effective survey methods have positioned avifauna as focal species in ecological restoration research. This article delves into the effects of habitat restoration on avifaunal distribution, revealing a tapestry of positive outcomes. Restored habitats witness increased avian community diversity and evenness, heightened habitat heterogeneity, and greater densities of avian and migratory species. Avifauna's presence also facilitates breeding success, reduces nest parasitism, and fosters additional foraging and breeding grounds. Furthermore, habitat restoration has shown remarkable successes in reviving songbird populations in fragmented forests and rescuing endangered species like red-crowned cranes. In light of the transformative impact of avian restoration, understanding the effects of restoration on avifauna is pivotal in guiding management activities of restored sites. Implementing strategic management approaches such as predator control, maintaining habitat heterogeneity, controlling nest parasites, reintroducing natural disturbance regimes, and selecting appropriate plant species ensures a nurturing environment for avian survival. Additionally, promoting a heterogeneous environment in aquatic systems has proved crucial in enhancing bird diversity. Improving ongoing research and adaptive management practices further empowers restoration efforts, allowing us to compose a symphony of avian abundance, resilience, and harmonious coexistence with the natural world.

Brain and antennal transcriptomes of host ants reveal potential links between behaviour and the functioning of socially parasitic colonies.

Insect social parasites are characterized by exploiting the hosts' social behaviour. Why exactly hosts direct their caring behaviour towards these parasites and their offspring remains largely unstudied. One hypothesis is that hosts do not perceive their social environment as altered and accept the parasitic colony as their own. We used the ant Leptothorax acervorum, host of the dulotic, obligate social parasite Harpagoxenus sublaevis, to shed light on molecular mechanisms underlying behavioural exploitation by contrasting tissue-specific transcriptomes in young host workers. Host pupae were experimentally (re-)introduced into fragments of their original, another conspecific, heterospecific or parasitic colony. Brain and antennal mRNA was extracted and sequenced from adult ants after they had lived in the experimental colony for at least 50 days after eclosion. The resulting transcriptomes of L. acervorum revealed that ants were indeed affected by their social environment. Host brain transcriptomes were altered by the presence of social parasites, suggesting that the parasitic environment influences brain activity, which may be linked to behavioural changes. Transcriptional activity in the antennae changed most with the presence of unrelated individuals, regardless of whether they were conspecifics or parasites. This suggests early priming of odour perception, which was further supported by sensory perception of odour as an enriched function of differentially expressed genes. Furthermore, gene expression in the antennae, but not in the brain corresponded to ant worker behaviour before sampling. Our study demonstrated that the exploitation of social behaviours by brood parasites correlates with transcriptomic alterations in the central and peripheral nervous systems.

Collocating pipelines to minimize fragmentation: evaluating ecological costs of a shale gas mitigation practice

AbstractShale gas development occurs in forests of the Appalachian Basin within breeding habitat for forest songbirds. Development requires linear infrastructure (e.g., pipelines, gas access roads) that fragments habitat and reduces core forest. Collocation is a mitigation practice that sites new pipelines adjacent to existing surface disturbance such as forest roads; it reduces core forest loss but may have associated ecological costs, defined as negative effects on native species and ecosystems. We conducted a paired sampling design between forest roads and collocated pipelines (expanded gas access roads collocated with pipelines) to evaluate ecological costs to forest songbirds in 2013 in Pennsylvania, USA. We surveyed 4 focal songbird species: 3 territorial species that varied in habitat requirements and the non‐territorial brown‐headed cowbird (Molothrus ater), an obligate brood parasite. We used spot mapping to survey focal species within linear corridors and the adjacent mature forest. Territory density of forest interior ovenbirds (Seiurus aurocapilla) was significantly lower on collocated pipelines (5.1 fewer territories per 10 ha) compared to forest road sites. We found no effect of collocation on territory density for the early successional species, eastern towhee (Pipilo erythrophthalmus) and chestnut‐sided warbler (Setophaga pensylvanica). Territories of all 3 territorial focal species crossed collocated pipeline sites less frequently than forest roads (ovenbird: 16%, eastern towhee: 14%, chestnut‐sided warbler: 31%) and the barrier effect increased with increasing corridor width. In contrast, brown‐headed cowbird abundance was 15 times greater at collocated pipelines compared to forest roads, suggesting that wider gas corridors provide enhanced access routes for cowbirds. Our study indicates the expansion of forest roads to collocated pipelines exacerbates the negative ecological effects already present with the existing road including increased edge avoidance by a forest interior species, greater barrier effects for all 3 territorial forest songbirds, and increased access for brown‐headed cowbirds into core forest. We support collocation as a mitigation strategy but emphasize restricting overall corridor width to reduce the additional ecological costs associated with this practice.

Factors influencing low incidence of double brooding in the Great Reed Warbler

Double brooding, the laying of a second clutch after successfully fledging young from a first nest in a season, is a common reproductive strategy among short-lived birds to increase annual breeding success. Nevertheless, there is widespread intra- and interspecific variation in the probability of producing a second clutch. Given that the frequency of double brooding could affect population growth rate, knowing what factors contribute to this phenomenon is also important in the conservation management of threatened facultative double-brooded species. Here, we examine the frequency of double brooding and the factors affecting the probability of this reproductive strategy in a population of the Great Reed Warbler, Acrocephalus arundinaceus, in south-western Slovakia. Results of a 15-year study (2008–2022) revealed low overall rate of double brooding in the Great Reed Warbler (5.6% per year, 0–15.4%). The length of breeding season, timing of the first clutch laying date and the size of the first broods were key factors influencing the female's decision to initiate a second clutch. On the other hand, successful brood parasitism did not affect second clutch initiation, which contrasts with our prediction. Given that only monogamous or primary females initiated a second clutch after successfully rearing a first one, we assume that producing two broods within the same season may be an alternative strategy for monogamous males to increase their annual reproductive output in this facultatively polygynous species. Therefore, due to relatively high rate of polygyny, we probably cannot expect higher rate of double broodings in the Great Reed Warbler in the future either.

Impacts of brood parasitism by shiny cowbird Molothrus bonariensis on the breeding success of a small host, the black-backed water tyrant Fluvicola albiventer.

The shiny cowbird Molothrus bonariensis parasitizes many species with different life-history traits and has a detrimental effect on the survival of the progeny of the hosts. In response, hosts have developed numerous antiparasitic defenses. Here, we examined the effects of brood parasitism by shiny cowbird on the clutch and brood sizes (83 nests) in a small host, the black-backed water tyrant Fluvicola albiventer. We also studied whether the death of parasite nestlings was related to the care of the foster parents and whether the host had any antiparasitic defense against the shiny cowbird. Our results indicate that brood parasitism significantly decreased the host hatching and fledging successes. The majority of nest failures (57%) were caused by brood parasitism. Shiny cowbird parasitism occurred in 52% of nests and the intensity of parasitism was 1.23 ± 0.53 eggs per parasitized nest. Of the total host eggs, 54% were damaged. During the incubation stage, 20 nests (47%) were abandoned because of egg punctures by shiny cowbirds females. Only two parasitic fledglings were recorded, while the remaining nestlings either died from starvation (n = 12) or predation (n = 3). Foster parents abandoned parasitic nestlings between 5 and 10 days old. Our findings demonstrate that the shiny cowbird has very low rates of fledging success when parasitizing black-backed water tyrant. Also, parasitism had a high reproductive cost in the black-backed water tyrant because a very low proportion (7%) of the parasitized nests (n = 43) were successful.

Eggshell spots are an important cue for the egg retrieval behavior in two tit species.

It is a common occurrence for incubating female ground- or cavity-nesting birds to accidentally roll their own eggs out of the nest cup. To correctly roll eggs that are not in the nest cup back to the nest, birds must be able to discriminate between their eggs and things around their nests that could be easily confused for their eggs (e.g., egg-shaped stones or other birds' eggs). Moreover, there may be a strong interaction between egg retrieval and egg rejection behaviors in the context of avian brood parasitism where recognition and rejection of alien eggs is an effective means for hosts to defend against cuckoo parasitism. It has been shown that green-backed tits (Parus monticolus) and Japanese tits (P. minor) in China have strong egg recognition ability and are able to reject nonmimetic eggs in the nest. Eggshell spots play an essential role in the egg rejection behavior of these two tit hosts. This study investigated the egg retrieval behavior of green-backed tits and Japanese tits by adding one experimental egg to the nest corner to explore whether eggshell spots also play a role in the process of egg retrieval. The results revealed significant differences in the retrieval rates of white-rumped munia (Lonchura striata) eggs painted with spots, Japanese tits' own true eggs, and unpainted, pure white-white-rumped munia eggs. The retrieval rate of white-white-rumped munia eggs was significantly lower than that of spotted white-rumped munia eggs and Japanese tits' own spotted eggs. For green-backed tits, the retrieval rate of spotted white-rumped munia eggs in the nest corner was significantly higher than that of pure white-white-rumped munia eggs, while the rejection rate of spotted white-rumped munia eggs was significantly lower than that of pure white-white-rumped munia eggs. These findings indicate that eggshell spots play a key role in the egg retrieval of green-backed tits and Japanese tits.

When perfection isn't enough: host egg signatures are an effective defence against high-fidelity African cuckoo mimicry.

Most mimicry systems involve imperfect mimicry, whereas perfect and high-fidelity mimicry are rare. When the fidelity of mimicry is high, mimics might be expected to have the upper hand against their antagonists. However, in coevolving systems, diversification of model phenotypes may provide an evolutionary escape, because mimics cannot simultaneously match all model individuals in the population. Here we investigate high-fidelity mimicry in a highly specialized, Afrotropical brood parasite-host system: the African cuckoo and fork-tailed drongo. Specifically, we test whether host egg polymorphisms are an effective defence against such mimicry. We show, using a combination of image analysis, field experiments and simulations, that: (1) egg colour and pattern mimicry of fork-tailed drongo eggs by African cuckoos is near-perfect on average; (2) drongos show fine-tuned rejection of foreign eggs, exploiting unpredictable pattern differences between parasitic eggs and their own; and (3) the high degree of interclutch variation (polymorphic egg 'signatures') exhibited by drongos gives them the upper hand in the arms race, with 93.7% of cuckoo eggs predicted to be rejected, despite cuckoos mimicking the full range of drongo egg phenotypes. These results demonstrate that model diversification is a highly effective defence against mimics, even when mimicry is highly accurate.

Increasing perceived predation risk through playbacks reduces Red-winged Blackbird abundance in agriculture late in the breeding season

Abstract Perceived predation and brood parasitism risks strongly influence nesting habitat selection in several bird species. Here, we report on a playback experiment evaluating whether perceived predation or brood parasitism risk can reduce Red-winged Blackbird (Agelaius phoeniceus) abundances in agricultural nesting habitat. We broadcast Cooper’s Hawk vocalizations (Accipiter cooperii, a predator of adult blackbirds and nests), Brown-headed Cowbird vocalizations (Molothrus ater, a brood parasite of many passerine species, including blackbirds), and the “Sonic Net” as treatments, the latter of which is broadcast of frequencies that overlap with blackbird vocalizations and prevent blackbirds from accessing intraspecific communication informing of predator and brood parasite risks. Neither the hawk, cowbird, nor Sonic Net treatments reduced blackbird abundances at sites early in the breeding season (April to May), when blackbirds were selecting nesting habitat. In contrast, late in the breeding season (July to August), hawk vocalizations and the Sonic Net reduced blackbird abundances at sites, but cowbird vocalizations did not. Our late-breeding season results suggest that blackbirds may flexibly change responses to perceived predation risk based on their stage of reproductive investment. Perceived predation risk could potentially be used to manage pest birds that nest in agricultural landscapes, at least for crops that are vulnerable to birds late in the breeding season.