Azure-winged Magpie Research Articles

Breeding stages affect egg recognition in azure-winged magpies (Cyanopica cyanus)

Egg rejection often involves a cognitive process of recognizing foreign eggs, which can vary not only between species or among different individuals of the same species, but also within the same individual during different breeding stages, leading to markedly different responses to parasitic eggs. We conducted a comparative study in Wuhan, Hubei, and Fusong, Jilin, China, on the recognition and rejection behavior of azure-winged magpies (Cyanopica cyanus) at different breeding stages (pre-egg-laying, one-host-egg, multi-host-egg and early incubation stages). In the Fusong population, there was a significant difference in the rejection rate of model eggs by azure-winged magpies at different stages of the egg-laying period. During the one-host-egg stage, the rejection rate (63.6%) was significantly lower than that during the pre-egg-laying stage (85.7%) and the multi-host-egg stage (100%). The population of azure-winged magpies in Wuhan exhibited a 100% rejection rate towards model eggs during the pre-egg-laying stage. Furthermore, during the incubation stage, azure-winged magpies were able to accurately recognize and reject foreign eggs even when those were in majority. This indicates that azure-winged magpies employ a template-based recognition mechanism rather than relying on discordance mechanism for recognition after the onset of incubation. This study suggests that while azure-winged magpies can truly recognize their own eggs, different breeding stages still influence their rejection response towards parasitic eggs, especially during the pre-egg-laying and egg laying stages.

Does presence of top predator improve forest birds' survival and diversity? An ecological case study assessing umbrella conservational impact of tiger using carrion

After hunting, predators tend to leave a large amount of carrion behind. It is widely reported that this resource is commonly used by various species in the ecosystem and is essential for the survival of scavengers, particularly in winter. Although recent studies are focused on mammals, little is known about how this works with facultative scavenger birds, which may lead to a serious underestimation of the key role that top predators such as the Amur tiger (Panthera tigris altaica) play in ecosystems. Here, we conducted a field feeding experiment to quantitatively evaluate the effects of Amur tiger on avian scavengers by simulating their predation residue. The results show that the Corvidae is the main bird species that consumes carrion, while woodpeckers and some insectivorous songbirds also benefit from the remains that Amur tiger leaves behind. We assumed that in winter, if the daily energy demand for the six main scavenger birds completely relied on the predation residues of Amur tiger separately, the prey remains of one Amur tiger could feed about 28 crows, 49 Azure-winged magpies, 61 Eurasian jays, 235 Eurasian nuthatches, 96 Great spotted woodpeckers, or 385 Willow tits. It means that the prey remains of top predators like Amur tiger may be an extremely important resource to avian scavengers and carrion could be a potential ecological indicator of Amur tiger keystone effect. This study provides experimental evidence from the field for the first time, and reveals the ecological mechanism of the role of keystone species of the Amur tiger, i.e., how to indirectly protect other animal groups in the forest ecosystem that have important ecological value for the biodiversity and the health of local forest vegetation through the protection of the Amur tiger.

Distribution patterns of breeding nests in the colonial-breeding Azure-winged Magpie Cyanopica cyanus

ABSTRACT Capsule Distribution patterns of the breeding nests of the Azure-winged Magpie can help to understand spatial and temporal changes in core use areas throughout the breeding range. Aims We investigated the spatial and temporal patterns of nest locations in the breeding colony, to determine the effect of breeding experience and timing on the nest location of Azure-winged Magpies. Methods We collected data on the nest locations of Azure-winged Magpies in a breeding colony and analysed them to identify patterns in nest location. We estimated the nest distribution range through a kernel density analysis, using a geographic information system. Results The size and location of the core use area of the breeding population changed in the following breeding season when the previous year's reproductive success rate was low. We also observed changes in the size and location of the core-use area in relation to the timing of breeding. Conclusion Inter-annual change of the core use area was associated with the timing of breeding and the population's breeding experience.

Optimizing the baiting strategy for oral vaccine delivery to wild boar

Baits are a means of orally delivering toxicants, medicaments, or chemical markers to wild boar and feral pigs (Sus scrofa). We tested three bait types, the paraffin-feed-sugar-based IREC bait (green and colorant-free versions), a puffed leguminous bait with the same flavoring as the IREC bait (Flavor), and a plain puffed leguminous bait without flavoring (Plain). Baits were deployed in a fenced hunting estate with year-round feeding to assess bait type preference and study the effect of bait flavoring and coloring, pre-feeding, baiting device, and habituation on bait consumption and bait selectivity. Baits were deployed under heavy pavel stones, targeting adult wild boar, or in piglet-selective feeders. The main bait consumer was the wild boar (IREC 54%; Flavor 15%; Plain 16%) followed by azure-winged magpies (Cyanopica cooki; IREC 11%; Flavor 8%; Plain 17%). The most consumed bait was IREC (n = 164; 71%, mean 4.1 baits per site/day), followed by Flavor (102; 40%; 2.5) and Plain (70; 29%; 1.7). Pre-feeding increased bait consumption of all bait types (IREC 92%; Flavor 63%; Plain 40%). IREC baits were more consumed when deployed under stones (86%) than when deployed in piglet feeders (57%), while no difference between baiting devices was observed for Flavor and Plain baits. Birds preferred color-free baits (consumption ratio of 10% for color-free baits and 0% for green baits), while no other animal showed color preference. We suggest using green IREC-type baits, deployed after pre-baiting using species- and age-specific baiting devices.ResumenLos cebos son un medio para administrar por vía oral tóxicos, medicamentos o marcadores a jabalíes y cerdos salvajes (Sus scrofa). Probamos tres tipos de cebo, el cebo IREC a base de parafina y azúcar (versiones verdes y sin colorantes), un cebo de leguminosas infladas con el mismo sabor que el cebo IREC (Flavor) y el mismo cebo de leguminosas sin sabor (Plain). Los cebos se colocaron en una finca de caza cercada con alimentación durante todo el año para evaluar la preferencia del tipo de cebo y estudiar el efecto del sabor y color del cebo, el precebado, el dispositivo de cebo y la habituación sobre el consumo y la selectividad. Los cebos se colocaron debajo de piedras, dirigidos a jabalíes adultos, o en comederos selectivos para rayones. El principal consumidor fue el jabalí (IREC 54%; Sabor 15%; Sencillo 16%) seguido del rabilargo (Cyanopica cooki; IREC 11%; Flavor 8%; Plain 17%). El cebo más consumido fue IREC (n = 164; 71%, media 4,1 cebos por sitio/día), seguido de Flavor (102; 40%; 2,5) y Plain (70; 29%; 1,7). El precebado aumentó el consumo de todos los tipos de cebo (IREC 92%; Flavor 63%; Plain 40%). Los cebos IREC se consumieron más cuando se colocaron bajo piedras (86%) que cuando se dispusieron en comederos para rayones (57%), mientras que no se observaron diferencias entre dispositivos para los demás cebos. Las aves prefirieron los cebos sin color (proporción de consumo del 10% para cebos sin color y 0% para cebos verdes), mientras que ningún otro animal mostró preferencia en función del color. Sugerimos utilizar cebos verdes tipo IREC, distribuidos tras un precebado y utilizando dispositivos específicos para cada especie y edad.

Sounding the alarm: Functionally referential signaling in Azure-winged Magpie

Functionally referential signals are a complex form of communication that conveys information about the external environment. Such signals have been found in a range of mammal and bird species and have helped us understand the complexities of animal communication. Corvids are well known for their extraordinary cognitive abilities, but relatively little attention has been paid to their vocal function. Here, we investigated the functionally referential signals of a cooperatively breeding corvid species, Azure-winged Magpie (Cyanopica cyanus). Through field observations, we suggest that Azure-winged Magpie uses referential alarm calls to distinguish two types of threats: ‘rasp’ calls for terrestrial threats and ‘chatter’ calls for aerial threats. A playback experiment revealed that Azure-winged Magpies responded to the two call types with qualitatively different behaviors. They sought cover by flying into the bushes in response to the ‘chatter’ calls, and flew to or stayed at higher positions in response to ‘rasp’ calls, displaying a shorter response time to ‘chatter’ calls. Significant differences in acoustic structure were found between the two types of calls. Given the extensive cognitive abilities of corvids and the fact that referential signals were once thought to be unique to primates, these findings are important for expanding our understanding of social communication and language evolution.

Correlation of personality with individual reproductive success in shrub-nesting birds depends on their life history style

Two questions in the research of animal personality—whether there is a correlation between a personality trait and individual reproductive success, and what is the genetic basis underlying a personality trait—remain unresolved. We addressed these two questions in three shrub-nesting birds, the Azure-winged Magpie (Cyanopica cyanus, AM), White-collared Blackbird (Turdus albocinctus, WB), and Brown-cheeked Laughingthrush (Trochalopteron henrici, BL). The personality type of an individual was first identified according to its response to a territorial intruder. Then, we compared the fleeing distance, breeding parameters, and differential expressed genes (DEGs) in the brain transcriptome between bold and shy breeders. In the three species, bold breeders exhibited more aggressiveness towards an intruder of their territory than did shy breeders. The reproductive success of bold breeders was significantly higher than that of shy breeders in AM but not in WB and BL. The three species shared one DEG, crabp1, which was up-regulated in bold relative to in shy individuals. By regulating the expression of corticotropin-releasing hormone, higher crabp1 gene expression can decrease cellular response to retinoic acid. Therefore, bold individuals are insensitive to external stresses and able to exhibit more aggressiveness to intruders than their shier counterparts. Aggressiveness is beneficial to bold individuals in AM but not in WB and BL because the former could evoke neighbors to make the same response of defending against intruders but the latter could not. Although a personality trait may have the same genetic basis across species, its correlation with reproductive success depends largely on the life history style of a species.

Responses of birds to observers holding popguns: Hunting history influences escape behavior of urban birds.

Human activities affect bird behavior both directly and indirectly. Birds constantly regulate their behavior in response to human disturbance. Gun hunting, a major directional disturbance, puts enormous selection pressure on birds. In China, gun bans have been in place for nearly 30 years, and little hunting using guns occurs in modern cities. However, little attention has been paid to whether a history of hunting still affects the behavioral adaptations of urban birds. In this study, we compared the flight initiation distance (FID) of the Eurasian tree sparrow Passer montanus, Azure-winged magpie Cyanopica cyanus, Common hoopoe Upupa epops and Eurasian magpie Pica pica in the presence of observers with or without popguns. The Eurasian tree sparrow, Azure-winged magpie, and Eurasian magpie effectively recognized the difference between the observers, and perceived the armed observer as a greater threat, exhibiting earlier escape behavior, but this phenomenon was not found in the Common hoopoe. The different expressions in FID of experimental bird species in China cities may be affected by the different levels of recognition of hunting pressure due to different hunting histories.

Testing the effects of kinship, reciprocity and dominance on prosocial food provisioning in azure‐winged magpies (Cyanopica cyana), carrion crows (Corvus corone) and common ravens (C. corax)

AbstractProsocial behaviour (i.e. benefitting others without receiving a direct gain) has long been perceived as an evolutionary puzzle but is nevertheless relatively common among non‐human animals. Prosocial food provisioning has recently been documented in several large‐brained bird species, such as corvids and parrots. Yet, to date, little is known about which factors influence food provisioning in these species. Here, we investigated whether kinship, reciprocity and dominance affected food provisioning in the group service paradigm in three corvid species, namely azure‐winged magpies (Cyanopica cyana), carrion crows (Corvus corone) and common ravens (C. corax). In this paradigm, the subjects are tested in their regular social groups and can choose to make food available to their group members by landing on a simple seesaw apparatus. We found no evidence for an effect of kinship or reciprocity on food provisioning. Contrary to our predictions, the subjects' dominance was not positively correlated with their rate of food provisioning in any species. Among ravens, dominance was instead positively correlated with receiving food. We conclude that preferential provisioning for kin and direct reciprocity might have been impeded by the provider's inability to control who receives the food in the group service paradigm, but that our findings provide another piece of evidence that dominance is a highly important factor in the social interactions of common ravens.

Landscape factors influencing bird nest site selection in urban green spaces

IntroductionUnderstanding the birds’ breeding strategies in urban habitats is vital for ensuring their continued existence. Therefore, more research must be conducted on bird breeding and urban adaptation strategies in urban green spaces. This study aimed to address this gap by investigating the influence of landscape factors on the selection of bird nest sites. MethodsData on the presence and absence of magpie (Pica pica) and gray magpie (Cyanopica cyana) nests were collected through field surveys conducted in the campus of Nanjing Forestry University during the 2023 breeding season. Generalized additive models (GAMs) incorporating landscape variables were employed to assess the effects of these predictors on nest occurrence. The model with the lowest Akaike’s information criterion value was selected among the candidate GAMs.ResultsBelow is a summary of the main results. Nest tree height (TH), distance from the central lawn (D), and tree coverage (TC) within the sampled area were identified as the primary landscape factors influencing nest site choice. Conversely, factors such as the shortest distance to the water source, herb coverage, shrub coverage, percentage of buildings, and percentage of hard pavement did not significantly impact on nest site selection. Furthermore, the nesting potential of magpies and grey magpies initially increased with tree height, reaching a maximum at ca. TH=25 meters after which it began to decline. The nesting occurrence rate showed an initial decrease tendency with increasing distance from the central lawn, reaching a minimum at D=400 meters, and then increased with further distance. Additionally, nesting potential decreased initially with increasing of TC in the range of 0–20%, fluctuated evenly between 20–60% TC, and decreased rapidly when TC exceeded 60%.DiscussionThis study provides valuable insights into the selection of nest sites by birds in urban habitats, specifically with respect to landscape factors. The understanding of the impact of urban green spaces on urban birds and the underlying mechanisms of their behavior contributes to the conservation of wild birds and promotes the harmonious development of urban areas.

The Use of the Microstructure of Coverling Feathers in the Systematics of Ground Jays (Aves, Corvidae: <i>Podoces, Eupodoces</i>)

Using scanning electron microscopy, new data on the microstructure of the definitive coverling feathers of all four species of ground jays Podoces pleskei, P. panderi, Eupodoces hendersoni and E. biddulphi and eight other species of Corvidae were obtained: Ptilostomus afer, Garrulus glandarius, Perisoreus infaustus, Corvus cornix, Cyanopica cyana, Nucifraga caryocatactes, Pica pica and Pyrrhocorax pyrrhocorax. Comparative morphological analysis involving previously published data on the microstructure of the pen-feathers of these species, as well as Corvus monedula, C. frugilegus, C. corax, revealed a number of feather microstructures specific to ground jay species, as well as differences between Podoces and Eupodoces, which confirms their genus status, possible relationship with G. glandarius and Pt. afer, as well as the preservation of ancestral features in P. pleskei.

The use of plastic litter as nesting material by the azure-winged magpie Cyanopica cyanus in an agricultural environment of South Korea.

In bird species, anthropogenic nesting materials have been known to have a negative effect on the survival of birds in general, but in some species, these can be used instead of natural materials, which can have a positive effect on the structural aspects of nests. Our study aims to investigate the type and amount of anthropogenic materials found in the nests of the colonial breeding azure-winged magpie (Cyanopica cyanus) in an agricultural area, as well as the characteristics of these used for each nest structure. We found that plastic litter was used in all of the azure-winged magpie breeding nests observed, and the types and amounts of plastic litter used differed between the cup and the outer. In all nests, soft, elastic, and insulating materials such as polyester fiber were mainly observed in the cup, and strings that weave and anchor branches and soil from nature were mostly found in the outer. The amount of plastic litter used in nests was related to the size of the nest. Plastic litter used in nests is thought to be collected from agricultural materials used in agricultural lands, vinyl greenhouses, and agricultural warehouses in our study site. Consequently, we expect that the phenomenon of azure-winged magpies using plastic litters for nest building may be common situation for the current agricultural environment where plastics are widespread.

To Mob or Not to Mob: Habitat and Time of Day Influence in Mobbing Behavior in the Azure-Winged Magpie (Cyanopica cookii).

While mobbing, individuals utter distinctive calls and perform visual threatening displays. Like any other antipredatory strategies, it involves some costs (time, energy, injuries, and even death). Therefore, mobbing would be expected to vary depending on the perceived magnitude of the predation risk. Moreover, harassment behavior can also serve as a demonstration of social status and to teach juveniles to recognize predators and related behaviors. Therefore, mobbing could also persist even when predation risk is particularly low. To test our hypotheses, we used tawny owl playbacks and a taxidermy mount to elicit the mobbing response in azure-winged magpies throughout the daylight period. To classify mobbing intensity, we created five categories depending on the proximity to the owl model at which the mobbing was performed. The results revealed that mobbing behavior in azure-winged magpies was more intense where predation risk was higher: in the most suitable habitat for the tawny owl, the forest, although considerable levels of mobbing were found in the dehesa and the ecotone, which indicate that mobbing has different purposes. However, we did not find statistically significant differences in mobbing intensity depending on the time of the day. We could not show a daily adjustment of antipredator response, but magpies modulated mobbing depending on the perceived risk linked to the habitat.

Influence of age, breeding state and approach direction on sensitivity to human gaze: a field study on Azure-winged magpies.

In predator-prey interactions, various factors affect the prey's perception of risk and decision to flee. Gaze sensitivity, the ability to react to the presence, direction, or movement of the head and eyes, has been reported in many birds. However, few studies have focussed on variation in sensitivity to human gaze in relation to other risks and potential breeding costs. Here, we studied the influence of human gaze on the escape behaviour of Azure-winged magpies (Cyanopica cyanus) and investigated the effects of breeding state (breeding season and nonbreeding season) and approach direction on gaze sensitivity. In Experiment 1, we tested whether magpies showed different sensitivities to human gaze according to age class and breeding state when approached directly. The results showed that the breeding state could affect the flight initiation distance (FID), with adults in the breeding season having a shorter FID compared to those in the nonbreeding season. Meanwhile, only adults were found to be averse to direct human gaze and juveniles showed no sensitivity. In Experiment 2, we conducted three different gaze treatments on adultmagpies in the breeding season under three bypass distances (0m, 2.5m, 5m). The results showed that approach direction had no effect on FID, while the sensitivity to human gaze differed under three bypass distances. Adults could clearly recognise human head and eye direction at a certain bypass distance (2.5m). Our study reveals the cognitive ability of Azure-winged magpies to human head and eye direction and the effects of age, breeding state and approach direction, which may provide further insights into human-wildlife interactions, especially for birds in urban habitats.

Egg rejection and egg recognition mechanism in a Chinese Azure-winged Magpie (Cyanopica cyanus) population

Recognition and rejection of foreign eggs are effective defense of hosts against brood parasitism. However, brood parasitism can impose various selection pressures on different geographic populations of the same host species. In a multiple cuckoo system in China, Azure-winged Magpies (Cyanopica cyanus) are parasitized by both Indian Cuckoos (Cuculus micropterus) and Asian Koels (Eudynamys scolopaceus). In this study, egg recognition ability and recognition mechanism of the Azure-winged Magpie were investigated using a population in Fusong, southeastern Jilin, China. The results showed that 55.6% (20/36) of the Azure-winged Magpies correctly rejected quail (Coturnix japonica) eggs in their nests, while 13.9% (5/36) of the individuals experienced rejection costs by wrongly rejecting their own eggs. Azure-winged Magpies could accurately reject the experimental eggs when the number of such eggs in the nests was the same as that of the magpie eggs. However, Azure-winged Magpies do not recognize and reject conspecific eggs (0/28). The present study indicates that the Azure-winged Magpie has moderate egg recognition ability toward non-mimetic quail eggs and shows a true recognition mechanism with rejecting foreign eggs by accurately recognizing their own eggs. However, they cannot recognize conspecific eggs.

Vocal repertoire of Azure-winged Magpies (Cyanopica cyanus): A context-associated communication system

Signals within animals’ vocal communication are considered functional referential and context-specific. Even in the absence of the context, receivers are expected to acquire the information of calls and respond specifically. Whereas the framework was supported by plenty of evidence, its exhaustivity in describing all animal vocalisations has been questioned. Here, we investigated the vocal repertoire of a cooperatively breeding species, Azure-winged Magpie (Cyanopica cyanus), to present evidence for referential signals. The results showed that Azure-winged Magpies had a relatively large vocal repertoire, consisting of twelve distinct calls. These calls were associated with the context including movement, begging for food, contact, vigilance against predators, etc. However, even the predator-specific alarm calls would induce various responses of receivers. This implies that multiple pieces of information are involved in the vocalisation, which could be utilised by the receiver to select an appropriate response based on the surroundings. Our study gives a detailed description of the context and function of the vocal repertoire in Azure-winged Magpies, laying the foundation for further investigation on the developmental mechanisms of bird vocalisations. This study also suggests that the referential signals of animal vocalisations may not be limited to the context-specific responses of receivers and need to be discussed from a broader perspective.

물까치(Cyanopica cyanus)의 형태학적 측정에 의한 성 판별

Most sexually monomorphic species, including the family Corvidae, are visually indistinguishing in field investigations. We investigated intersexaul morphological differences of the Azure-winged magpie (Cyanopica cyanus). We caught 86 adults (67 males, 14 females, and 5 unidentified), measured their morphological characteristics (head-bill length, bill length, maximum and minimum wing length, tarsus length, body length, tail length, and weight), and collected blood samples. Sex was determined by PCR amplification using the previously used P2/P8 (Griffiths et al. 1998) primers. Statistical analysis was used to compare morphological differences between sexes. Males were longer in body length and maximum wing length, and discriminant function analysis using the two variables showed the sex was distinguished with an accuracy of 71.7%. We discussed the significance of the two variables in the monomorphic Azure-winged magpies.

A comparative study of mirror self-recognition in three corvid species

Mirror self-recognition (MSR) assessed by the Mark Test has been the staple test for the study of animal self-awareness. When tested in this paradigm, corvid species return discrepant results, with only the Eurasian magpies and the Indian house crow successfully passing the test so far, whereas multiple other corvid species fail. The lack of replicability of these positive results and the large divergence in applied methodologies calls into question whether the observed differences are in fact phylogenetic or methodological, and, if so, which factors facilitate the expression of MSR in some corvids. In this study, we (1) present new results on the self-recognition abilities of common ravens, (2) replicate results of azure-winged magpies, and (3) compare the mirror responses and performances in the mark test of these two corvid species with a third corvid species: carrion crows, previously tested following the same experimental procedure. Our results show interspecies differences in the approach of and the response to the mirror during the mirror exposure phase of the experiment as well as in the subsequent mark test. However, the performances of these species in the Mark Test do not provide any evidence for their ability of self-recognition. Our results add to the ongoing discussion about the convergent evolution of MSR and we advocate for consistent methodologies and procedures in comparing this ability across species to advance this discussion.

Genomic signatures and evolutionary history of the endangered blue-crowned laughingthrush and other Garrulax species

BackgroundThe blue-crowned laughingthrush (Garrulax courtoisi) is a critically endangered songbird endemic to Wuyuan, China, with population of ~323 individuals. It has attracted widespread attention, but the lack of a published genome has limited research and species protection.ResultsWe report two laughingthrush genome assemblies and reveal the taxonomic status of laughingthrush species among 25 common avian species according to the comparative genomic analysis. The blue-crowned laughingthrush, black-throated laughingthrush, masked laughingthrush, white-browed laughingthrush, and rusty laughingthrush showed a close genetic relationship, and they diverged from a common ancestor between ~2.81 and 12.31 million years ago estimated by the population structure and divergence analysis using 66 whole-genome sequencing birds from eight laughingthrush species and one out group (Cyanopica cyanus). Population inference revealed that the laughingthrush species experienced a rapid population decline during the last ice age and a serious bottleneck caused by a cold wave during the Chinese Song Dynasty (960–1279 AD). The blue-crowned laughingthrush is still in a bottleneck, which may be the result of a cold wave together with human exploitation. Interestingly, the existing blue-crowned laughingthrush exhibits extremely rich genetic diversity compared to other laughingthrushes. These genetic characteristics and demographic inference patterns suggest a genetic heritage of population abundance in the blue-crowned laughingthrush. The results also suggest that fewer deleterious mutations in the blue-crowned laughingthrush genomes have allowed them to thrive even with a small population size. We believe that cooperative breeding behavior and a long reproduction period may enable the blue-crowned laughingthrush to maintain genetic diversity and avoid inbreeding depression. We identified 43 short tandem repeats that can be used as markers to identify the sex of the blue-crowned laughingthrush and aid in its genetic conservation.ConclusionsThis study supplies the missing reference genome of laughingthrush, provides insight into the genetic variability, evolutionary potential, and molecular ecology of laughingthrush and provides a genomic resource for future research and conservation.

A diagnosis model of parental care: How parents optimize their provisioning strategy in brood reduction?

Altricial birds often display biased preferences in providing parental care for their dependent offspring, especially during food shortages. During this process, such inflexible rules may result in provisioning errors. To demonstrate how parents optimize their provisioning strategies, we proposed a "diagnosis model" of parental care to posit that parents will undergo a diagnosis procedure to test whether selecting against some particular offspring based on phenotype is an optimal strategy. We tested this model in an asynchronous hatching bird, the Azure-winged Magpie Cyanopica cyanus, based on 10 years of data about demography and parental provisioning behaviors. Given their higher daily survival rates, core offspring (those hatched on the first day) merits an investment priority compared with their marginal brood mates (those hatched on later days). However, a marginal offspring also merited a priority if it displayed greater weight gain than the expected value at the early post-hatching days. Parents could detect such a marginal offspring via a diagnosis strategy, in which they provisioned the brood at the diagnosis stage by delivering food to every nestling that begged, then biased food toward high-value nestlings at the subsequent decision stage by making a negative response to the begging of low-value nestlings. In this provisioning strategy, the growth performance of a nestling became a more reliable indicator of its investment value than its hatching order or competitive ability. Our findings provide evidence for this "diagnosis model of parental care" wherein parents use a diagnosis method to optimize their provisioning strategy in brood reduction.

Nest characteristics and composition of the colonial nesting Azure-winged magpie Cyanopica cyanus in South Korea.

Bird nests are crucial for reproductive success since they serve as structures to hold the eggs and nestlings safely. Therefore, the structural characteristics of bird nests have optimally evolved to maximize reproductive success, which are known to be affected by various factors. We gathered information on the nest characteristics such as nest structure and constituent materials in the colonial breeding Azure-winged magpie (Cyanopica cyanus) and investigated the relationship between ecologically relevant factors and the size and mass of the nests. The Azure-winged magpie nest can be deconstructed into an outer nest and an inner cup, and the type and mass of materials used for the construction of each part varies. Compared to the inner cup, the outer nest, which constitutes the overall shape of the nest, is composed of relatively harder materials, such as branches and soil. In contrast, the inner cup, which is the part where birds directly incubate eggs and raise nestlings, is composed of more flexible and softer materials, such as fiber and moss. We found that there was no relationship between nest characteristics and ecologically relevant factors. However, as the breeding season progressed, the volume of the inner cup decreased with increasing ambient temperatures. Our results show that Azure-winged magpies use differing materials for structurally distinct parts of the nests during construction. The results also indirectly suggest that the choice regarding the amount of insulating materials relative to changing temperatures during the breeding season may be one of the more significant adaptive strategies in the nest-building behaviors of Azure-winged magpies.