Wild zebra finches do not use social information from conspecific reproductive success for nest site choice and clutch size decisions

Information about the quality of local habitat can greatly help to improve an individual’s decision-making and, ultimately, its fitness. Nevertheless, little is known about the mechanisms and significance of information use in reproductive decisions, especially in unpredictable environments. We tested the hypothesis that perceived breeding success of conspecifics serves as a cue for habitat quality and hence influences breeding decisions (nest site choice and clutch size), using the zebra finch (Taeniopygia guttata) as a model species. Zebra finches breed opportunistically in the unpredictable, arid zone of Australia. They often inspect the nests of conspecifics, potentially to prospect on conspecific reproductive success, i.e., to collect social information. We conducted a clutch and brood size manipulation to experimentally create the perception of high and low quality areas. In six areas, clutch sizes of almost 300 zebra finch nests were either all increased (N = 3 areas) or reduced (N = 3 areas) throughout one breeding season. The number of breeding pairs and sizes of newly laid clutches were not significantly affected by the manipulated reproductive success of the areas. Thus, zebra finches did not use social cues for their reproductive decisions, which contrasts with findings of species in temperate zones, and could be an adaptation to the high unpredictability of their habitat. Even the personal experience of rebreeding birds did not directly affect their clutch size. Our study suggests that zebra finches employ a high level of opportunism as a key strategy for reproduction. Further, this is the first study to our knowledge using an experimental approach in the wild to demonstrate that decision-making in unpredictable natural environments might differ from decision-making in temperate environments with seasonal breeding

Begging calls provide social cues for prospecting conspecifics in wild zebra finches

Social information can spread fast and help animals adapt in fluctuating environments. Prospecting on the breeding sites of others, a widespread behavior, can help to maximize reproduction by, for instance, settling in the same area as other successful breeders. Previous studies have shown that successful broods have the highest number of prospectors and that they are visited most when offspring in nesting sites are already old, making the information more reliable. In this field study, we experimentally tested how prospectors are attracted to successful nest sites. We presented wild Zebra Finches (Taeniopygia guttata) with different visual or acoustic cues in nest boxes, simulating the presence of small or large clutches or broods. More Zebra Finches visited experimental nests that were associated with playback recordings of begging calls of large broods (7 chicks) as opposed to begging calls of small broods (3 chicks) and controls (white noise and silence). On the other hand, visual cues (nests with different numbers of eggs or rocks), representing nests at early stages, did not influence either the probability of visits, nor number or duration of visits. We present the first evidence that begging calls of chicks in the nest, a signal intended for kin communication, can also provide social information to unrelated prospecting conspecifics. This information could potentially be used for a fast initial assessment of the quality of a breeding site

Early-life social environment predicts social network position in wild zebra finches

Early-life experience can fundamentally shape individual life-history trajectories. Previous research has suggested that exposure to stress during development causes differences in social behaviour later in life. In captivity, juvenile zebra finches exposed to elevated corticosterone levels were less socially choosy and more central in their social networks when compared to untreated siblings. These differences extended to other aspects of social life, with ‘stress-exposed’ juveniles switching social learning strategies and juvenile males less faithfully learning their father's song. However, while this body of research suggests that the impacts of early-life stress could be profound, it remains unknown whether such effects are strong enough to be expressed under natural conditions. Here, we collected data on social associations of zebra finches in the Australian desert after experimentally manipulating brood sizes. Juveniles from enlarged broods experienced heightened sibling competition, and we predicted that they would express similar patterns of social associations to stress-treated birds in the captive study by having more, but less differentiated, relationships. We show striking support for the suggested consequences of developmental stress on social network positions, with our data from the wild replicating the same results in 9 out of 10 predictions previously tested in captivity. Chicks raised in enlarged broods foraged with greater numbers of conspecifics but were less ‘choosy’ and more central in the social network. Our results confirm that the natural range of variation in early-life experience can be sufficient to predict individuals' social trajectories and support theory highlighting the potential importance of developmental conditions on behaviour

The performance of field sampling for parasite detection in a wild passerine

Parasites can impact the behavior of animals and alter the interplay with ecological factors in their environment. Studying the effects that parasites have on animals thus requires accurate estimates of infections in individuals. However, quantifying parasites can be challenging due to several factors. Laboratory techniques, physiological fluctuations, methodological constraints, and environmental influences can introduce measurement errors, in particular when screening individuals in the wild. These issues are pervasive in ecological studies where it is common to sample study subjects only once. Such factors should be carefully considered when choosing a sampling strategy, yet presently there is little guidance covering the major sources of error. In this study, we estimate the reliability and sensitivity of different sampling practices at detecting two internal parasites-Serratospiculoides amaculata and Isospora sp.-in a model organism, the great tit Parus major. We combine field and captive sampling to assess whether individual parasite infection status and load can be estimated from single field samples, using different laboratory techniques-McMaster and mini-FLOTAC. We test whether they vary in their performance, and quantify how sample processing affects parasite detection rates. We found that single field samples had elevated rates of false negatives. By contrast, samples collected from captivity over 24 h were highly reliable (few false negatives) and accurate (repeatable in the intensity of infection). In terms of methods, we found that the McMaster technique provided more repeatable estimates than the mini-FLOTAC for S. amaculata eggs, and both techniques were largely equally suitable for Isospora oocysts. Our study shows that field samples are likely to be unreliable in accurately detecting the presence of parasites and, in particular, for estimating parasite loads in songbirds. We highlight important considerations for those designing host-parasite studies in captive or wild systems giving guidance that can help select suitable methods, minimize biases, and acknowledge possible limitations. Keywords: McMaster; fecal egg count; field sampling; mini‐FLOTAC; parasite infection; repeatability

The presence of air sac nematodes in passerines and near-passerines in southern Germany

Major climatic changes in conjunction with animal movement may be associated with the spread of parasites and their vectors into new populations, with potentially important consequences for population persistence. Parasites can evolve to adapt to unsuitable ecological conditions and take up refuge within new host species, with consequences for the population growth of the new host species. One parasite species that has likely been increasing its geographic range, and potentially infecting new hosts, is the recently described air sac nematode Serratospiculoides amaculata, in great tits (Parus major) in Slovakia. In this study, we screened wild birds for potential air sac nematode infection in a woodland area of southern Germany. We identified four additional host species: Eurasian nuthatch, great spotted woodpecker, greenfinch and robin. As infection by this group of nematodes can be highly pathogenic, we recommend further investigation into its potential risk to these populations

Age-related differences in the cloacal microbiota of a wild bird species

Background: Gastrointestinal bacteria play a central role in the health of animals. The bacteria that individuals acquire as they age may therefore have profound consequences for their future fitness. However, changes in microbial community structure with host age remain poorly understood. We characterised the cloacal bacteria assemblages of chicks and adults in a natural population of black-legged kittiwakes (Rissa tridactyla), using molecular methods. Results: We show that the kittiwake cloaca hosts a diverse assemblage of bacteria. A greater number of total bacterial OTUs (operational taxonomic units) were identified in chicks than adults, and chicks appeared to host a greater number of OTUs that were only isolated from single individuals. In contrast, the number of bacteria identified per individual was higher in adults than chicks, while older chicks hosted more OTUs than younger chicks. Finally, chicks and adults shared only seven OTUs, resulting in pronounced differences in microbial assemblages. This result is surprising given that adults regurgitate food to chicks and share the same nesting environment. Conclusions: Our findings suggest that chick gastrointestinal tracts are colonised by many transient species and that bacterial assemblages gradually transition to a more stable adult state. Phenotypic differences between chicks and adults may lead to these strong differences in bacterial communities. These data provide the framework for future studies targeting the causes and consequences of variation in bacterial assemblages in wild birds

Wild zebra finches choose neighbours for synchronized breeding

Organisms should aim to time their reproduction to match the optimal ecological conditions and thus maximize their fitness. However, social cues have been identified as determinants of reproductive decisions and might also be involved in coordinating the timing of reproduction. Breeding synchronously with other individuals can bring several advantages, including a reduced individual predation risk and an increased opportunity for social foraging. The behavioural mechanisms underlying reproductive synchrony are versatile and not well understood, particularly in species inhabiting unpredictable environments. In contrast to highly seasonal environments, more variable and unpredictable environments can support periods of extended breeding with lower levels of synchronous breeding overall, but opportunities for individuals to breed synchronously at a finer temporal and spatial scale. Zebra finches, Taeniopygia guttata, are a highly social species, naturally inhabiting the ecologically unpredictable arid zone of Australia. In the wild, reproduction at a broad population level is not highly synchronized and, at any time during a period of breeding activity, reproductive attempts can be found at different stages. However, previous work has suggested that at a finer spatial scale neighbours tend to breed at approximately the same time. Using nestboxes, we tested whether wild zebra finches preferentially seek to settle and initiate a breeding attempt adjacent to conspecifics at an early stage of breeding (nest building), as opposed to others at later stages of breeding and with which the opportunity to breed synchronously was reduced or absent. Pairs were more likely to initiate egg laying in nestboxes close to conspecifics at an early stage of breeding, suggesting that they do try to maximize the level of synchronicity with neighbours. Our results indicate the importance of social effects on both the phenology and spatial distribution of breeding

The social transmission of stress in animal collectives

The stress systems are powerful mediators between the organism's systemic dynamic equilibrium and changes in its environment beyond the level of anticipated fluctuations. Over- or under-activation of the stress systems' responses can impact an animal's health, survival and reproductive success. While physiological stress responses and their influence on behaviour and performance are well understood at the individual level, it remains largely unknown whether-and how-stressed individuals can affect the stress systems of other group members, and consequently their collective behaviour. Stressed individuals could directly signal the presence of a stressor (e.g. via an alarm call or pheromones), or an acute or chronic activation of the stress systems could be perceived by others (as an indirect cue) and spread via social contagion. Such social transmission of stress responses could then amplify the effects of stressors by impacting social interactions, social dynamics and the collective performance of groups. As the neuroendocrine pathways of the stress response are highly conserved among vertebrates, transmission of physiological stress states could be more widespread among non-human animals than previously thought. We therefore suggest that identifying the extent to which stress transmission modulates animal collectives represents an important research avenue.publishe

Ein Fall verblüffend irreführender Spechtfärbung: der bedrohte WellenohrspechtDryocopus galeatusist einCeleus

The Helmeted Woodpecker Dryocopus galeatus is a threatened species of the Atlantic Forest in southeastern South America. It has traditionally been placed in the genus Dryocopus, but it shows similarities in plumage and structure with woodpeckers in the genus Celeus. We sequenced mitochondrial and nuclear DNA that was sampled from live captured Helmeted Woodpeckers. We found that the Helmeted Woodpecker has a phylogenetic position embedded within the genus Celeus, and recommend its taxonomic treatment as Celeus galeatus. The Helmeted Woodpecker belongs to a clade within Celeus that includes Kaempfer?s Woodpecker C. obrieni, Rufous-headed Woodpecker C. spectabilis, and Cream-coloured Woodpecker C. flavus. It has the southernmost distribution range of the woodpeckers in this clade. The Helmeted Woodpecker is sympatric throughout its range with LineatedWoodpecker Dryocopus lineatus and Robust Woodpecker Campephilus robustus and these species from three different genera show a remarkable convergence in plumage colours and patterns. With the inclusion of Helmeted Woodpecker in Celeus, this genus has four out of 15 species on the International Union for Conservation of Nature (IUCN) red list, a higher proportion of red listed species than in the woodpecker family overall.Der Wellenohrspecht ist eine bedrohte Spechtart der atlantischen Wälder im Südosten Südamerikas. Er wurde traditionellerweise in das Genus Dryocopus eingeordnet, weist aber in Gefieder und Struktur Ähnlichkeiten zur Gattung Celeus auf. Wir sequenzierten mitochondriale und nukleare DNA aus Proben, die lebend gefangenen Individuen entnommen worden waren. Wir fanden heraus, dass der Wellenohrspecht phylogenetisch innerhalb der Gattung Celeus positioniert ist und empfehlen, ihn in dieses Genus zu klassifizieren. Dieser Specht gehört zu einer Stammlinie innerhalb von Celeus, die den Kaempferspecht Celeus obrieni, Zimtkopfspecht C. spectabilis und den Strohspecht C. flavus enthält. Er stellt den südlichsten Vertreter dieser Gruppe dar. Sein Verbreitungsgebiet deckt sich mit jenen des Linienspechts Dryocopus lineatus und des Scharlachkopfspechts Campephilus robustus und diese drei Arten aus verschiedenen Genera weisen eine bemerkenswerte Konvergenz in Gefiederfärbung und -muster auf. Zusammen mit dem Wellenohrspecht beinhaltet die 15 Arten zählende Gattung Celeus vier auf der Roten Liste der IUCN stehende Arten, mehr als der Durchschnitt der Familie.Fil: Lammertink, J. Martjan. Provincia de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Universidad Autónoma de Entre Ríos. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Santa Fe. Centro de Investigaciones Científicas y Transferencia de Tecnología a la Producción; Argentina. Proyecto Selva de Pino Paraná; ArgentinaFil: Kopuchian, Cecilia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Centro de Ecología Aplicada del Litoral. Universidad Nacional del Nordeste. Centro de Ecología Aplicada del Litoral; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Brandl, Hanja B.. University of Veterinary Medicine; AustriaFil: Tubaro, Pablo Luis. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Museo Argentino de Ciencias Naturales "Bernardino Rivadavia"; ArgentinaFil: Winkler, Hans. University of Veterinary Medicine; Austri

Under the weather: corticosterone levels in wild nestlings are associated with ambient temperature and wind

Animals time reproductive events to overlap with periods of favorable environmental conditions. However, weather conditions can be unpredictable. Young animals may be particularly susceptible to extreme weather during sensitive developmental periods. Here, we investigated the effects of adverse weather conditions on corticosterone levels (a hormone linked to the avian stress response) and body condition of wild nestling zebra finches (Taeniopygia guttata). We sought to tease apart the direct versus indirect (i.e. parental) effects of weather on nestling physiology and condition by increasing parental work load with a clutch manipulation experiment. We found that high temperatures were associated with lower levels of restraint-induced corticosterone and high wind speeds were associated with higher levels of baseline corticosterone. We found no associations between weather and nestling body condition. However, clutch manipulation did affect body condition, with nestlings from experimentally enlarged clutches in worse condition compared to nestlings from experimentally reduced clutches. Our findings suggest that weather can directly affect wild nestlings via changes in corticosterone levels. Further research is needed to understand how changes in corticosterone levels affect phenotype and survival in wild nestlings. Understanding how developing animals respond to changes in environmental predictability and extreme weather is vital for understanding the potential for rapid adaptation in the face of changing climatic conditions.publishe