Outdoor Aviaries Research Articles

A prenatal acoustic signal of heat reduces a biomarker of chronic stress at adulthood across seasons.

During development, phenotype can be adaptively modulated by environmental conditions, sometimes in the long-term. However, with weather variability increasing under climate change, the potential for maladaptive long-term responses to environmental variations may increase. In the arid-adapted zebra finch, parents emit "heat-calls" when experiencing heat during incubation, which adaptively affects offspring growth in the heat, and adult heat tolerance. This suggests that heat-call exposure may adjust individual phenotype to hot conditions, potentially compromising individual sensitivity to cool weather conditions. To test this hypothesis, we manipulated individual prenatal acoustic and postnatal thermal experiences during development, and sought to assess subsequent chronic responses to thermal fluctuations at adulthood. We thus measured heterophil to lymphocyte (H/L) ratios in adults, when held in outdoor aviaries during two summers and two winters. We found that birds exposed to heat-calls as embryos, had consistently lower H/L ratios than controls at adulthood, indicative of lower chronic stress, irrespective of the season. Nonetheless, in all birds, the H/L ratio did vary with short-term weather fluctuations (2, 5 or 7days), increasing at more extreme (low and high) air temperatures. In addition, the H/L ratio was higher in males than females. Overall, while H/L ratio may reflect how individuals were being impacted by temperature, heat-call exposed individuals did not show a stronger chronic response in winter, and instead appeared more resilient to thermal variability than control individuals. Our findings therefore suggest that heat-call exposure did not compromise individual sensitivity to low temperatures at adulthood. Our study also reveals that prenatal sound can lead to long-term differences in individual physiology or quality/condition, as reflected by H/L ratios, which are consistent with previously-demonstrated reproductive fitness differences.

Biological validation of faecal corticosterone metabolites as a non-invasive stress assessment in translocated California valley quail (Callipepla californica).

US quail species are vulnerable to population declines as a result of climate change, habitat loss and habitat fragmentation, all of which can result in physiological stress. Additionally, population restoration techniques (PRTs), like translocations, also induce stress. Traditional assessments of avian stress hormone levels include capturing and handling birds to extract blood, methods that are inherently stressful and can compound stress analyses. However, the stress hormone corticosterone (CORT) is metabolized from the blood and excreted in faeces as faecal corticosterone metabolites (FCMs). FCMs have been used as a non-invasive measurement of stress hormone levels in a variety of species, but must be validated for each species. The objective of this study was to biologically validate the use of FCMs as a non-invasive measurement of CORT levels in California valley quail (Callipepla californica). Reference and treatment quail were acclimated for 3 weeks in an outdoor aviary. Subsequently, treatment quail were subjected to a simulated 48-h translocation, a common and stress hormone-inducing PRT. Faecal samples were collected every 4h and processed using an enzyme immunoassay. Mean FCM concentrations of treatment quail (41.50 ± 16.13ng/g) were higher than reference FCM concentrations (24.07 ± 10.4ng/g). These results biologically validate the use of FCMs as a non-invasive method to assess CORT levels in California valley quail, demonstrate diurnal variation in quail CORT levels, and confirm that quail translocations are a stress-inducing PRT. Ultimately, this research validates a new non-invasive tool for stress response measurement to advance quail research, management and conservation.

Eating in the city: Experimental effect of anthropogenic food resources on the body condition, nutritional status, and oxidative stress of an urban bioindicator passerine.

Urban areas provide a constant and predictable supply of anthropogenic processed food. The House Sparrow (Passer domesticus Linnaeus, 1758), a declining urban bioindicator species, has recently been reported to have a high level of oxidative stress, with urban diet or pollutants proposed as the potential cause. In this study, we aimed to experimentally determine the effects of two urban trophic resource types (bar snack food leftovers and pet food) on sparrows' physical condition, plasma biochemical nutritional parameters, and blood oxidative status in captivity. To exclude the potential previous effect of urban pollutants, 75 House Sparrows were captured from a rural area in SE Spain and kept in outdoor aviaries. Individuals were exposed to one of three diet treatments: control diet (fruit, vegetables, poultry grain mixture), bar snack diet (ultra-processed snacks), or cat food diet (dry pellets) for 20 days. Blood samples were collected before and after diet treatments to analyze the relative change rates of 12 variables, including physical condition, nutritional status, and oxidant-antioxidant status. A principal component analysis was run to identify gradients of variables covariation, and Generalized Linear Mixed Models were used to determine the effect of diets on each selected PC and on raw variables. The bar snack diet led to signs of anemia and malnutrition, and females tended to lose body condition. The cat food diet increased oxidative stress indicators and protein catabolism. Unbalanced urban diets can affect the body condition and nutritional physiology of House Sparrows and may also induce oxidative stress despite the absence of environmental pollution.

Fatal Sarcocystis calchasi hepatitis in a captive Indian ringneck parakeet (Psittacula krameri manillensis)

An adult Indian ringneck parakeet (Psittacula krameri manillensis) from an outdoor aviary in Sacramento, California was found dead on the nest box. Postmortem examination showed firm, enlarged, yellow‑tinged liver and splenomegaly. Multifocal to coalescing, acute necrosis with macrophages, lymphocytes, plasma cells, and periportal ductular reaction were seen on liver histology with extra- and intracellular schizonts and merozoites. A few schizonts and lymphohistiocytic inflammation were seen in the spleen. Toxoplasma gondii, Sarcocystis neurona, S. falcatula and Neospora caninum were ruled out by immunohistochemistry. PCR of the liver for Sarcocystis spp. Based on the positive amplification/PCR of ITS1 segment and sequencing of 28S rRNA fragment, S. calchasi was confirmed. The splanchnic presentation of S. calchasi in this parakeet resembles the acute infection described experimentally in domestic pigeons (Columba livia f. domestica) and cockatiels (Nymphicus hollandicus). Since large populations of red-tailed hawks (Buteo jamaicensis) and Cooper's hawk (Accipiter cooperi), the likely definitive hosts of S. calchasi in North America, inhabit the Sacramento area, their presence near outdoor aviaries may account for the source of S. calchasi infective sporocysts.

Multi-view Tracking, Re-ID, and Social Network Analysis of a Flock of Visually Similar Birds in an Outdoor Aviary

The ability to capture detailed interactions among individuals in a social group is foundational to our study of animal behavior and neuroscience. Recent advances in deep learning and computer vision are driving rapid progress in methods that can record the actions and interactions of multiple individuals simultaneously. Many social species, such as birds, however, live deeply embedded in a three-dimensional world. This world introduces additional perceptual challenges such as occlusions, orientation-dependent appearance, large variation in apparent size, and poor sensor coverage for 3D reconstruction, that are not encountered by applications studying animals that move and interact only on 2D planes. Here we introduce a system for studying the behavioral dynamics of a group of songbirds as they move throughout a 3D aviary. We study the complexities that arise when tracking a group of closely interacting animals in three dimensions and introduce a novel dataset for evaluating multi-view trackers. Finally, we analyze captured ethogram data and demonstrate that social context affects the distribution of sequential interactions between birds in the aviary.

Nonlethal Effects of Predation: The Presence of Insectivorous Birds (Parus major) Affects The Behavior and Level of Stress in Locusts (Schistocerca gregaria)

Insect exposure to their predators can affect individuals and community processes, through direct consumption or nonlethal effects. However, the links between behavioral and physiological responses and stimuli needed for the development of predator avoidance are not clear. We subjected desert locusts (Schistocerca gregaria) to three nonlethal treatments, using great tits (Parus major) as a predator. The treatments included: (1) bird—presence of a great tit and its calls, (2) call—great tit calls only, (3) control—absence of a great tit and its calls. In the first behavioral laboratory experiment, locusts were offered food and shelter in an open space. The duration of hiding versus feeding indicated predator responses. In the second laboratory experiment, locusts were subjected to the same three treatments, and adipokinetic hormone (AKH) levels were measured in the central nervous system (CNS) and hemolymph. In the third experiment in an outdoor aviary, birds were allowed to fly freely over locusts before we measured physiological response. During the first experiment, locusts hid for a significantly longer amount of time and fed for a significantly shorter amount of time when the bird was present and calls were played, compared to when only calls were played or compared to the control treatment. The proximity of birds to locusts in the laboratory experiment elicited a significant increase in AKH levels in the CNS and hemolymph compared to the call/control treatment. The physical proximity of the great tits affected both the behavioral and physiological responses of the locusts.

Low Antioxidant Glutathione Levels Lead to Longer Telomeres: A Sex-Specific Link to Longevity?

Telomeres are repetitive DNA sequences at the end of chromosomes that protect them from degradation. They have been the focus of intense research because short telomeres would predict accelerated ageing and reduced longevity in vertebrates. Oxidative stress is considered a physiological driver of the telomere shortening and, consequently, short lifespan. Among molecules fighting against oxidative stress, glutathione is involved in many antioxidant pathways. Literature supports that oxidative stress may trigger a compensatory "hormetic" response increasing glutathione levels and telomere length. Here, we tested the link between total glutathione concentration and telomere length in captive birds (zebra finches; Taeniopygia guttata). Total glutathione levels were experimentally decreased during birds' growth using a specific inhibitor of glutathione synthesis (buthionine sulfoximine; BSO). We monitored the birds' reproductive performance in an outdoor aviary during the first month of life, and their longevity for almost 9 years. Among control individuals, erythrocyte glutathione levels during development positively predicted erythrocyte telomere length in adulthood. However, BSO-treated females, but not males, showed longer telomeres than control females in adulthood. This counterintuitive finding suggests that females mounted a compensatory response. Such compensation agrees with precedent findings in the same population where the BSO treatment increased growth and adult body mass in females but not males. BSO did not influence longevity or reproductive output in any sex. However, early glutathione levels and adult telomere length interactively predicted longevity only among control females. Those females with "naturally" low (non-manipulated) glutathione levels at the nestling age but capable of producing longer telomeres in adulthood seem to live longer. The results suggest that the capability to mount a hormetic response triggered by low early glutathione levels can improve fitness via telomere length. Overall, the results may indicate a sex-specific link between glutathione and telomere values. Telomerase activity and sexual steroids (estrogens) are good candidates to explain the sex-biased mechanism underlying the early-life impact of oxidative stress on adult telomere length.

Effects of short-term experimental manipulation of captive social environment on uropygial gland microbiome and preen oil volatile composition

IntroductionAvian preen oil, secreted by the uropygial gland, is an important source of volatile compounds that convey information about the sender’s identity and quality, making preen oil useful for the recognition and assessment of potential mates and rivals. Although intrinsic factors such as hormone levels, genetic background, and diet can affect preen oil volatile compound composition, many of these compounds are not the products of the animal’s own metabolic processes, but rather those of odor-producing symbiotic microbes. Social behavior affects the composition of uropygial microbial communities, as physical contact results in microbe sharing. We experimentally manipulated social interactions in captive dark-eyed juncos (Junco hyemalis) to assess the relative influence of social interactions, subspecies, and sex on uropygial gland microbial composition and the resulting preen oil odor profiles.MethodsWe captured 24 birds at Mountain Lake Biological Station in Virginia, USA, including birds from two seasonally sympatric subspecies – one resident, one migratory. We housed them in an outdoor aviary in three phases of social configurations: first in same-sex, same-subspecies flocks, then in male-female pairs, and finally in the original flocks. Using samples taken every four days of the experiment, we characterized their uropygial gland microbiome through 16S rRNA gene sequencing and their preen oil volatile compounds via GC-MS.ResultsWe predicted that if social environment was the primary driver of uropygial gland microbiome composition, and if microbiome composition in turn affected preen oil volatile profiles, then birds housed together would become more similar over time. Our results did not support this hypothesis, instead showing that sex and subspecies were stronger predictors of microbiome composition. We observed changes in volatile compounds after the birds had been housed in pairs, which disappeared after they were moved back into flocks, suggesting that hormonal changes related to breeding condition were the most important factor in these patterns.DiscussionAlthough early life social environment of nestlings and long-term social relationships have been shown to be important in shaping uropygial gland microbial communities, our study suggests that shorter-term changes in social environment do not have a strong effect on uropygial microbiomes and the resulting preen oil volatile compounds.

Effects of manipulated food availability and seasonality on innate immune function in a passerine.

The innate immune system is essential for survival, yet many immune traits are highly variable between and within individuals. In recent years, attention has shifted to the role of environmental factors in modulating this variation. A key environmental factor is food availability, which plays a major role in shaping life histories, and may affect resource allocation to immune function through its effect on nutritional state. We developed a technique to permanently increase foraging costs in seed-eating birds, and leveraged this technique to study the effects of food availability on the innate immune system over a 3-year period in 230 zebra finches housed in outdoor aviaries. The immune components we studied were haptoglobin, ovotransferrin, nitric oxide, natural antibodies through agglutination, complement-mediated lysis, and killing capacity of Escherichia coli and Candida albicans, covering a broad spectrum of the innate immune system. We explored the effects of food availability in conjunction with other potentially important variables: season, age, sex and manipulated natal brood size. Increased foraging costs affected multiple components of the immune system, albeit in a variable way. Nitric oxide and agglutination levels were lower under harsh foraging conditions, while Escherichia coli killing capacity was increased. Agglutination levels also varied seasonally, but only at low foraging costs. C. albicans killing capacity was lower in winter, and even more so for animals in harsh foraging conditions that were raised in large broods. Effects of food availability on ovotransferrin were also seasonal, and only apparent in males. Haptoglobin levels were independent of foraging costs and season. Males had higher levels of immune function than females for three of the measured immune traits. Innate immune function was independent of age and manipulated natal brood size. Our finding that food availability affects innate immune function suggests that fitness effects of food availability may at least partially be mediated by effects on the immune system. However, food availability effects on innate immunity varied in direction between traits, illustrating the complexity of the immune system and precluding conclusions on the level of disease resistance.

Using skin temperature and activity profiles to assign chronotype in birds

Chronotypes describe consistent differences between individuals in biological time-keeping. They have been linked both with underlying variation in the circadian system and fitness. Quantification of chronotypes is usually by time of onset, midpoint, or offset of a rhythmic behaviour or physiological process. However, diel activity patterns respond flexibly to many short-term environmental influences, which can make chronotypes hard to identify. In contrast, rhythmic patterns in physiological processes, such as body temperature, may provide more robust insights into the circadian basis of chronotypes. These can be telemetrically recorded from skin-mounted, temperature-sensitive transmitters, offering minimally invasive opportunities for working on free-ranging animals in the wild. Currently, computational methods for deriving chronotype from skin temperature require further development, as time series are often noisy and incomplete. Here, we investigate such methods using simultaneous radio telemetry recordings of activity and skin temperature in a wild songbird model (Great Tit Parus major) temporarily kept in outdoor aviaries. Our aims were to first develop standardised selection criteria to filter noisy time series of skin temperature and activity, to second assign chronotype based on the filtered recordings, and to third compare chronotype as assigned based on each of the two rhythms. After the selection of rhythmic data using periodicity and autocorrelation parameters, chronotype estimates (onset and offset) were extracted using four different changepoint approaches for skin temperature and one approach for activity records. The estimates based on skin temperature varied between different approaches but were correlated to each other (onset: correlation coefficient r = 0.099–0.841, offset: r = 0.131–0.906). In contrast, chronotype estimates from skin temperature were more weakly correlated to those from activity (onset: r = −0.131–0.612, offset: r = −0.040– −0.681). Overall, chronotype estimates were less variable and timed later in the day for activity than for skin temperature. The distinctions between physiological and behavioural chronotypes in this study might reflect differences in underlying mechanisms and in responsiveness to external and internal cues. Thus, studying each of these rhythms has specific strengths, while parallel studies of both could inform broadly on natural variation in biological time-keeping, and may allow assessment of how biological rhythms relate to changes in the environment.

Experiment in semi-natural conditions did not confirm the influence of malaria infection on bird attractiveness to mosquitoes

BackgroundChanges in host phenotype following parasite infection are often considered as host manipulation when they seem advantageous for the parasite. However, putative cases of host manipulation by parasites are rarely tested in field-realistic conditions. Infection-induced phenotypic change cannot be conclusively considered as host manipulation if no evidence shows that this trait is adaptive for the parasite in the wild. Plasmodium sp., the parasites causing malaria in vertebrates, are hypothesized to “manipulate” their host by making their odour more attractive to mosquitoes, their vector and final host. While this is fairly well supported by studies on mice and humans, studies focusing on avian malaria give contradictory results.MethodsIn the present study, genotyped birds at different stages (uninfected, acute and chronic) of Plasmodium relictum infection were exposed, in a large outdoor aviary, to their natural vector, the mosquito Culex pipiens.ResultsAfter genotyping the blood meals of more than 650 mosquitoes, we found that mosquitoes did not bite infected birds more than they bit them before infection, nor more than they bit uninfected hosts.ConclusionsOur study highlights the importance of testing ecological behaviours under natural conditions and suggests that different processes might be at play in mammals and birds regarding potential manipulation of attractiveness by malaria parasites.Graphical

Experimentally manipulated food availability affects offspring quality but not quantity in zebra finch meso-populations

Food availability modulates survival, reproduction and thereby population size. In addition to direct effects, food availability has indirect effects through density of conspecifics and predators. We tested the prediction that food availability in isolation affects reproductive success by experimentally manipulating food availability continuously for 3 years in zebra finches (Taeniopygia guttata) housed in outdoor aviaries. To this end, we applied a technique that mimics natural variation in food availability: increasing the effort required per food reward without affecting diet. Lower food availability resulted in a slight delay of start of laying and fewer clutches per season, but did not affect clutch size or number of offspring reared per annum. However, increasing foraging costs substantially reduced offspring growth. Thus, food availability in isolation did not impact the quantity of offspring reared, at the expense of offspring quality. Growth declined strongly with brood size, and we interpret the lack of response with respect to offspring number as an adaptation to environments with low predictability, at the time of egg laying, of food availability during the period of peak food demand, typically weeks later. Manipulated natal brood size of the parents did not affect reproductive success. Individuals that were more successful reproducers were more likely to survive to the next breeding season, as frequently found in natural populations. We conclude that the causal mechanisms underlying associations between food availability and reproductive success in natural conditions may be more complex than usually assumed. Experiments in semi-natural meso-populations can contribute to further unravelling these mechanisms.

Observations on the Breeding Behavior of the Blakiston's Fish Owl (Bubo blakistoni) On Hokkaidō, Japan

ABSTRACT Blakiston's Fish Owl (also known as Blakiston's Eagle-Owl; Bubo blakistoni) is an endangered species that inhabits northeast Asia. Blakiston's Fish Owls were rare (approximately 70 individuals) on Hokkaidō, Japan, at the start of my study, but rigorous protection and intervention programs have led to more than a doubling of the population (approximately 165 individuals) since 1970. Despite its elusive nature and rarity, I have studied this owl species by direct observation and banding for 46 yr throughout Hokkaidō. I here report on little known aspects of its intraspecific interactions and breeding behavior (specifically, pair formation). Identification of individual birds was facilitated by color-banding (a total of 447 owls from 1985–2019). Most pair formations began with an individual male or female flying into the territory of a single owl of the opposite sex, duetting with the resident owl, and then the pair flying together through the forest. However, pair formation occasionally occurred by displacement of a member of an established pair; in some cases, a replacement male took over parental duties. Under government permit, I cared for injured owls, which were housed in large outdoor aviaries; these captive owls sometimes attempted to form pair bonds with wild birds in the area. To test the feasibility of “matchmaking” to increase the number of territorial pairs on Hokkaidō, I attempted to induce pairing of releasable captive birds with wild birds, or to release them into territories with single adults; these tests resulted in successful pair-bonding of the target birds in two cases. I here describe these observations of intraspecific interactions and pair formation to aid future conservation efforts for this endangered species.

Baby birds beat the heat thanks to singing parents

Baby zebra finches hatch into one of Earth's most inhospitable environments, the Australian outback, where summer temperatures can exceed 40°C. Fortunately, zebra finch parents can prepare their young for this dangerously hot climate by singing to them before they hatch. When temperatures rise above 26°C, parents emit ‘heat calls’ that warn their embryos of high environmental temperatures. Unlike their normal vocalizations, heat calls have a high-pitched frequency, a fast rhythm and can prompt embryos to develop differently in preparation for the heat. Notably, birds that are serenaded by heat calls as embryos tend to be relatively small, a characteristic thought to help them lose heat more efficiently and produce more young throughout adulthood. Despite the lasting influence of heat calls on zebra finch physiology, the mechanism through which they act remains a mystery.Led by Eve Udino (Deakin University, Australia), a team of researchers also from Deakin University, Clemson University, USA, and the Doñana Biological Station, Spain, questioned whether the energy-generating units inside cells (mitochondria) are the missing piece to this musical puzzle. Mitochondria use oxygen to convert food into cellular energy (ATP), while a portion of this oxygen is also diverted to produce heat. Since changes in mitochondrial function during development can have long-term effects on animal physiology, Udino and colleagues suggested that zebra finch mitochondria may be responding to heat calls produced by their parents. The team collected eggs from zebra finches maintained at an outdoor aviary in Geelong, Australia, and incubated the eggs at a blistering 37.5°C. A few days before they were due to hatch, the team played recordings of heat calls to the developing embryos. The newly hatched chicks were then raised in nests at various temperatures, ranging from 22°C to 34°C. Once they turned 13 days old, the team obtained some blood from the chicks to assess the function of the mitochondria in their red blood cells.The researchers first discovered that nest temperature can alter how well zebra finch mitochondria work. The birds raised in hotter nests had less efficient mitochondria, meaning that their mitochondria produced less ATP and consequently more heat than the mitochondria of birds raised at cooler temperatures. Remarkably, embryonic exposure to heat calls improved mitochondrial efficiency across all nest temperatures (22–34°C), suggesting that heat calls re-program how zebra finch mitochondria balance ATP versus heat production.While a nest temperature of 34°C may seem hot, zebra finches can experience temperatures that are much, much higher. Therefore, Udina and colleagues took the study one step further and exposed a group of the 13-day-old birds to a brief heatwave, warming the youngsters’ nests to 44°C over the course of 2.5 hours before checking the mitochondria again. This time, the mitochondria of birds that had listened to heat calls as embryos tended to be less efficient. Although this may seem disadvantageous, the team suspects that there may be benefits to reducing mitochondrial efficiency under extreme heat conditions. High rates of mitochondrial ATP production can produce toxic reactive oxygen species, compounds that can wreak havoc on proteins, lipids and DNA. Making mitochondria less efficient at extremely high temperatures may help birds reduce the damaging effects of reactive oxygen species.We often think that a bird's life begins once it hatches, but birds can sense and respond to events going on in the outside world before they enter it. As zebra finch parents sound the heat alarm, their embryos get to work altering their physiology. So, next time you hear zebra finches calling in the Australian heat, don't think of their sweet songs as ‘music to the ears’, but rather, as ‘music to the mitochondria’.

How to Stay Cool: Early Acoustic and Thermal Experience Alters Individual Behavioural Thermoregulation in the Heat

Climate change is pushing organisms closer to their physiological limits. Animals can reduce heat exposure – and the associated risks of lethal hyperthermia and dehydration – by retreating into thermal refuges. Refuge use nonetheless reduces foraging and reproductive activities, and thereby potentially fitness. Behavioural responses to heat thus define the selection pressures to which individuals are exposed. However, whether and why such behavioural responses vary between individuals remains largely unknown. Here, we tested whether early-life experience generates inter-individual differences in behavioural responses to heat at adulthood. In the arid-adapted zebra finch, parents incubating at high temperatures emit “heat-calls,” which adaptively alter offspring growth. We experimentally manipulated individual early life acoustic and thermal experience. At adulthood, across two summers, we then repeatedly recorded individual panting behaviour, microsite use, activity (N = 2,402 observations for 184 birds), and (for a small subset, N = 23 birds) body temperature, over a gradient of air temperatures (26–38°C), in outdoor aviaries. We found consistent inter-individual variation in behavioural thermoregulation, and show for the first time in endotherms that early-life experience contributes to such variation. Birds exposed prenatally to heat-calls started panting at lower temperatures than controls but panted less at high temperatures. It is possible that this corresponds to a heat-regulation strategy to improve water saving at high temperature extremes, and/or, allow maintaining high activity levels, since heat-call birds were also more active across the temperature gradient. In addition, microsite use varied with the interaction between early acoustic and thermal experiences, control-call birds from cooler nests using the cooler microsite more than their hot-nest counterparts, whereas the opposite pattern was observed in heat-call birds. Overall, our study demonstrates that a prenatal acoustic signal of heat alters how individuals adjust behaviourally to thermal challenges at adulthood. This suggests that there is scope for selection pressures to act differently across individuals, and potentially strengthen the long-term fitness impact of early-life effects.

Usutu virus infection in aviary birds during the cold season

ABSTRACT The mosquito-borne flavivirus Usutu virus (USUV) is responsible for countless deaths in both resident populations and birds kept in outdoor aviaries. Since 2001, USUV outbreaks have attracted increased attention due to the rapid geographical spread of the virus and its close relationship to West Nile virus (WNV), an emerging pathogen in humans and animals. Similar to WNV, the USUV enzootic transmission cycle predominantly involves Culex spp. as vectors, whereas birds serve as amplifying reservoir hosts. In Europe, USUV-associated disease outbreaks in birds are almost exclusively described during late spring and early autumn (early April to late October). Contagiousness of virus particles excreted by infected birds has not yet been proven, so that the role of non-vector-borne transmission, as it is known for the closely related WNV, remains unclear. Here we report the diagnosis of USUV infection in 15 of 24 birds from mortality outbreaks that occurred during the cold season between late October 2018 and early April 2019, in eight different aviaries located in Germany. Detection of USUV was performed using standardized molecular biological methods and immunohistochemistry for verification of the infection. USUV infection in a parrot species, a tropical finch and two estrildid finches are reported for the first time. Further research on the occurrence of USUV infection during the cold season is key to understanding the dynamics of viral transmission as well as for a profound health risk assessment for aviary birds as well as humans.

Flexibility in thermal physiology and behaviour allows body mass maintenance in hibernating hazel dormice

AbstractStudying animals under natural or semi‐natural conditions is essential to better understand the implications of a warming climate on species survival. Here, we provide evidence of the effects of increasing winter ambient temperature (Ta) on the thermal physiology, feeding behaviour and body mass (BM) of a small mammalian hibernator, the hazel dormouse Muscardinus avellanarius. We collected skin temperature, metabolic rate (MR) and BM data from captive, hibernating dormice exposed to two winters of differing intensity in outdoor aviaries. Additionally, we obtained skin temperature data from one free‐ranging individual during the hibernation period. Statistical modelling showed that Ta and time since the start of hibernation both had significant non‐linear effects on the probability of arousal from torpor. During the warmer winter (Ta<0°C on 26 days), foraging resulted in higher BMs for some individuals, despite more frequent arousals, than during the colder winter (Ta<0°C on 86 days). As expected, Ta had a non‐linear effect on MR during torpor, with the lowest energy expenditure at intermediate Ta, and normothermic MR was minimal when Ta was warmer. The negative effect of increased arousal frequency on BM was counteracted by the positive effect of foraging on BM. Conforming with the accumulating body of evidence on high flexibility in physiological responses in many small mammals, we found that the thermoregulatory and behavioural responses of dormice during hibernation were more flexible than previously observed for this temperate, fat‐storing species. The ability to respond to prevailing environmental conditions might help M. avellanarius cope with increasing winter Ta predicted for ongoing global warming.

Isolation and characterization of low pathogenic H7N7 avian influenza virus from a red-crowned crane in a zoo in South Korea

BackgroundSouth Korea conducts annual national surveillance programs to detect avian influenza (AI) in domestic poultry, live bird markets, and wild birds. In March 2017, an AIV was isolated from fecal samples in an outdoor aviary flight cage in a zoo in Korea.ResultsNucleotide sequencing identified the isolate as low pathogenic avian influenza virus (LPAIV) H7N7, and DNA barcoding analysis identified the host species as red-crowned crane. This isolate was designated A/red-crowned crane/Korea/H1026/2017 (H7N7). Genetic analysis and gene constellation analysis revealed that A/red-crowned crane/Korea/H1026/2017 (H7N7) showed high similarity with four H7N7 LPAIVs isolated from wild bird habitats in Seoul and Gyeonggi in early 2017.ConclusionsConsidering the genetic similarity and similar collection dates of the viruses, and the fact that zoo bird cages are vulnerable to AIV, it is likely that fecal contamination from wild birds might have introduced LPAIV H7N7 into the red-crowned crane at the zoo. Therefore, our results emphasize that enhanced biosecurity measures should be employed during the wild bird migration season, and that continued surveillance should be undertaken to prevent potential threats to avian species in zoos and to humans.

Wintering Snow Buntings Elevate Cold Hardiness to Extreme Levels but Show No Changes in Maintenance Costs.

AbstractResident temperate passerines adjust their phenotypes to cope with winter constraints, with peak performance in metabolic traits typically occurring during the coldest months. However, it is sparsely known whether cold-adapted northern species make similar adjustments when faced with variable seasonal environments. Life in near-constant cold could be associated with limited flexibility in traits underlying cold endurance. We investigated this by tracking individual physiological changes over five consecutive winters in snow buntings (Plectrophenax nivalis), an Arctic-breeding migratory passerine typically confronted with nearly constant cold. Buntings were held in an outdoor aviary and exposed to seasonal temperature variation typical of temperate zone climates. We measured phenotypic changes in body composition (body, fat, and lean mass, pectoralis muscle thickness), oxygen transport capacity (hematocrit), metabolic performance (basal metabolic rate [BMR] and summit metabolic rate [Msum]), thermogenic endurance (time to reach Msum), and cold tolerance (temperature at Msum). Snow buntings showed flexibility in functions underlying thermogenic capacity and cold endurance comparable to that observed in temperate resident passerines wintering at similar latitudes. Specifically, they increased body mass (13%), fat mass (246%), hematocrit (23%), pectoralis muscle thickness (8%), and Msum (27%). We also found remarkable cold tolerance in these birds, with individuals reaching Msum in helox at temperatures equivalent to less than -90°C in air. However, in contrast with resident temperate passerines, lean mass decreased by 12%, and there was no clear increase in maintenance costs (BMR). Our results show that the flexibility of traits underlying thermal acclimatization in a cold-adapted northern species is comparable to that of temperate resident species living at lower latitudes and is therefore not limited by life in near-constant cold.

Experimental manipulation of mixed-species flocks reveals heterospecific audience effects on calling

Animal signallers are subject to audience effects when they alter communication due to changes in the presence or characteristics of receivers. Studies aimed at understanding audience effects have typically examined effects of conspecific audiences on signaller communication. Less work has focused on heterospecific audiences, which present an important avenue of research for species that participate in mixed-species groups. Here we experimentally tested mixed-species flocks of Carolina chickadees, Poecile carolinensis, and tufted titmice, Baeolophus bicolor, for conspecific and heterospecific audience effects. Birds were trapped from naturally occurring flocks and held in seminatural outdoor aviaries, where we recorded calling. We found that chickadees and titmice were sensitive to the number of conspecifics in flocks when communicating via ‘chick-a-dee’ calls, which are social cohesion calls produced by both species. Chickadees also were sensitive to the number of titmice in flocks, but chick-a-dee calling behaviour in titmice did not differ with regard to the number of chickadees in flocks. Furthermore, when subject to playbacks of simulated risk, chickadees and titmice produced more chick-a-dee calls when more titmice were in a flock. After these playbacks, chickadees produced fewer chick-a-dee calls with increasing numbers of conspecifics in flocks, whereas titmice produced more chick-a-dee calls with increasing numbers of conspecifics in flocks. These results suggest that chickadees and titmice are sensitive to social factors within their mixed-species flocks when communicating, and that chickadees appear more sensitive to heterospecific presence than do titmice. We suggest this is due to the dominance status of the species in these flocks, where titmice are typically dominant over chickadees.