Platycercus Elegans Research Articles

Beak and feather disease virus (BFDV) persists in tissues of asymptomatic wild Crimson Rosellas

Infectious diseases can drive populations and species to extinction. Beak and feather disease virus (BFDV) is a circovirus of global conservation concern that can infect all Psittaciformes and some other species. Yet some parrot species, such as Crimson rosellas (Platycercus elegans), can live successfully with high BFDV prevalence (>40%) with no clinical signs reported in infected individuals. We assessed BFDV load in 10-12 tissues per bird, from n = 66 P. elegans, to reveal tissue tropism and BFDV persistence in tissues. Here we show that in 94% of individuals, BFDV was detected in one or more tissues. While BFDV replicated to high levels in subadults, in adults (some confirmed seropositive) the virus persisted in various tissues at much lower levels. Our findings reveal that BFDV is much more common in wild P. elegans than previously thought and suggest that current screening practices (mostly on blood) may substantially underestimate BFDV infection estimates, with implications for biosecurity and conservation programs globally.

Interacting impacts of drought and fire on bird populations—insights from a long-term study in the Warrumbungles

ABSTRACT The interacting effects of drought and fire on ecological communities are poorly understood. Long-term studies in the Warrumbungle Mountains, central-west New South Wales, subject to drought and fire during the past 21 years, enabled their separate and combined effects to be quantified for individual species and functional groups. Insectivores (especially ground-foragers) dominated previous lists of declining species in this region of NSW and were also prominent in the present work. Insectivores were more likely to be drought- than fire-affected, with seven species declining due to drought, three to drought plus fire, and three to fire alone. Our analyses also revealed declines in a suite of honeyeaters (Meliphagidae), previously not reported as declining. Honeyeaters are major pollinators of eucalypts, so the loss of nectarivores and insectivores has far-reaching implications for pollination, recruitment, successional dynamics, and forest health. Four honeyeater species were adversely affected by drought, five by fire, and one by a combination of drought and fire. Drought and fire, alone or in combination, were implicated in declines of granivores, including the Crimson Rosella Platycercus elegans, and frugivores, especially the Mistletoebird Dicaeum hirundinaceum, the latter reflecting the loss of mistletoes in fire-affected landscapes, and foreshadowing additional losses due to the reliance on mistletoe by many species. Another group not previously identified as threatened, but declining due to drought were two omnivores, the Pied Currawong Strepera graculina and Australian Raven Corvus coronoides. Hollow-nesting birds including two species of treecreeper and the Laughing Kookaburra Dacelo novaeguineae fared badly. Several common Australian species were among the decliners, including Laughing Kookaburra, Willie Wagtail Rhipidura leucophrys and Australian Magpie Cracticus tibicen. We conclude that no suite of birds is exempt from these environmental stressors, and predict that, as droughts reduce populations at regional scales and fires diminish carrying capacity of critical habitats at landscape scales, rarer species will decline to local extinction while more commonly observed species will be reduced in abundance.

Worlding Eco-psychology: a Collective Bio-ethnography

AbstractIn this paper, eight practicing psychologists, a dog (Oscar), white cockatoos, crimson rosellas, blue gums, plum blossoms, the words of theorists of eco-psychology and post-humanism joined together for two days with the mountains of the Darug and Gundungurra peoples, to explore questions about psychology and its capacity to respond to the climate crisis. We designed a series of psychoterratic exercises for this purpose: (1) a bio-graphical definitional ceremony, (2) a series of short lectures and readings set to the poetics of open dialogue, (3) a sympoietic vegetal-thinking exercise, (4) a bush-psychogeography and (5) a final reflection on praxis. We present our findings, written in bricolage, a compost of experiences and ideas both horizontal and vertical, written, drawn and photographic.

A PCR-Based Retrospective Study for Beak and Feather Disease Virus (BFDV) in Five Wild Populations of Parrots from Australia, Argentina and New Zealand

The beak and feather disease virus (family Circovirdae) is a virus of concern in the conservation of wild Psittaciformes globally. We conducted a PCR screening for the beak and feather disease virus (BFDV) using samples collected during previous field studies (1993–2014) in five populations of parrots of the Southern Hemisphere: Eclectus parrots (Eclectus roratus) and Crimson rosellas (Platycercus elegans) from Australia, Burrowing parrots (Cyanoliseus patagonus) and Monk parakeets from Argentina (Myiopsitta monachus), and Forbes’ parakeet from New Zealand (Cyanoramphus forbesi). A total of 612 samples were screened. BFDV was not detected in any of the sampled birds. Our results provide a retrospective screening, covering three different tribes of Old and New World parrots, including two of the most numerous species, and contributing a large set of negative results. Furthermore, our results suggest that geographical and temporal differences in BFDV distribution may exist and merit further research, as a critical component in the efforts to manage the disease and its epidemiological aspects. The results presented here hold the potential to provide a baseline for future studies investigating the temporal evolution and the spread of BFDV.

Ability to detect antibodies to beak and feather disease virus in blood on filter paper decreases with duration of storage.

BackgroundBeak and feather disease virus (BFDV) is a circovirus that infects captive and wild psittacine birds, and is of conservation concern. The haemagglutination inhibition (HI) assay is used to determine antibody titres against BFDV, and the use of dried blood spots (DBS) on filter paper stored at room temperature has been suggested to be an equally valid technique to the use of frozen serum. However, research on other pathogens has found variable results when investigating the longevity of antibodies stored on DBS at room temperature. Consequently, we aimed to test the temporal stability of antibodies to BFDV in DBS samples stored long-term at room temperature. A further goal was to add to the current knowledge of antibody response to naturally acquired BFDV infection in crimson rosellas (Platycercus elegans).MethodsBlood was collected from wild P. elegans in Victoria, Australia, that had been live-trapped (n = 9) or necropsied (n = 11). BFDV virus load data were obtained from blood stored in ethanol by real-time quantitative PCR (qPCR); antibody titres were obtained by HI assay from either DBS or serum samples, which had been collected concurrently. All HI assays were performed commercially by the Veterinary Diagnostic Laboratory (VDL) in Charles Sturt University, Australia, who were blind to BFDV blood status.ResultsHI titres from DBS stored at room temperature declined significantly over time (~80 weeks). By contrast, frozen serum samples assayed after 80 weeks in storage all had high HI titres, only varying up to one dilution step from the initial HI titres obtained from DBS at 3–6 weeks after sampling. Weak HI titres from DBS samples all came back negative when the test was repeated only nine weeks later. Novel high HI titres were reported in P. elegans, and while most birds with high antibody titres had corresponding negative qPCR results, a single subadult presented with high HI titres and virus load simultaneously.ConclusionDetection of antibodies on filter paper stored at room temperature decreases over time, increasing the chances of false negatives in these samples, and in repeated testing of samples with weak HI titres. Consequently, serum should be the preferred sample type to use for seroepidemiological studies on BFDV in parrots and other bird species. When not possible, it may help to store DBS on filter paper at −20 °C or lower. However, prompt testing of DBS samples (e.g., <6 weeks in storage) is recommended pending further research on antibody temporal stability. We also show that P. elegans, especially adults, can produce high antibody titres against BFDV, which may help them resist infection.

Utilization of modified and artificial nests by endemic and introduced parrots on Norfolk Island

Animals that breed in cavities formed through decay or mechanical damage often face limitations to reproduction due to a shortage of nest sites. Artificial nests are commonly deployed to increase the short‐term availability of breeding sites for these species. Often this is an effective approach; however, artificial nests are costly and may be ignored by the target species or inadvertently benefit nontarget species. Here we consider the use of modified natural hollows and artificial nest sites to support endangered Norfolk Island green parrots Cyanoramphus cookii. We recorded the characteristics of all modified and artificial nests in the Norfolk Island National Park and used 8 years of nesting data to study nest selection by green parrots and introduced crimson rosellas Platycercus elegans. Artificial nests (those lacking a natural base) were never used by green parrots. Nests with thicker walls were more likely to be used by green parrots, but there was no nest site characteristic that predicted frequency of use. Crimson rosella nest use was not predicted by any of the nest characteristics measured. A better understanding of the reasons behind green parrots' avoidance of artificial nests and preference for thicker nest walls is required to inform the future design and management of nest sites. Our study shows that evaluation of how artificial sites are used by the target species is important to maximize the efficacy of conservation efforts.

Beak and feather disease virus and Chlamydiales infections in wild Australian psittacines: no statistical evidence for dependence

ABSTRACT Wildlife can be hosts for pathogens of conservation and zoonotic concern. Infection with one pathogen can increase the risk of co-infection with others, with resulting impacts on hosts, for example on body condition or survival. However, studies of co-infection in wild populations are rare. Globally, psittacine birds can be infected with beak and feather disease virus (BFDV), a circovirus of significant conservation concern, and with bacteria of the order Chlamydiales, including the zoonotic Chlamydia psittaci. These pathogens are common in Australian psittacines, and their putatively immunosuppressive effects would predict co-infection to be more common than expected due to chance alone. Here, we test this hypothesis across four abundant and widespread Australian parrot species: Crimson Rosella, Sulphur-crested Cockatoo, Galah and Blue-winged Parrot. Using wild-caught birds, we tested for pathogen DNA and, in the case of Chlamydiales, also antibodies, to investigate both current and previous infection status. We detected co-infection prevalence of up to 16.4% in the combined samples from the four species and up to 28.9% in Crimson Rosellas, the species with the largest sample size. Contrary to expectations, however, we found that the incidence of infections with the two pathogens was statistically independent. There was also no effect of co-infection on body condition or haematocrit. Our findings therefore suggest that while concurrent infection does occur, it is no more common than expected by chance. We discuss limitations of the data and suggest avenues for future research. Overall, our study provides insights that potentially benefit psittacine conservation, welfare, and human health.

A Crimson Rosella for Josephine

Abstract A hitherto unrecorded engraving, dated 1803, can now be shown to be the first depiction of an Australian Crimson Rosella (Platycercus elegans) made in France. The engraving was made by François Nicolas Martinet, the ornithological specialist famous for his work with the Comte de Buffon. Quite apart from the intrinsic interest of the image, its history sheds light on the earliest phase of the collection of Josephine Bonaparte at Malmaison, her property on the western outskirts of Paris, and the substantial work she was overseeing in the first years of the century, especially in respect of the natural history collections made during the voyage to Australia of Nicolas Baudin in 1800–04. The plate also provides the key to the story of Martinet’s final, abandoned publication, a work that was advertised in 1804 but never completed, copies of which are held in the Smithsonian Libraries and Archives and in Trinity College, Hartford, CT.

Species, sex and geographic variation in chlamydial prevalence in abundant wild Australian parrots

Chlamydia psittaci (order: Chlamydiales) is a globally distributed zoonotic bacterium that can cause potentially fatal disease in birds and humans. Parrots are a major host, yet prevalence and risk factors for infection in wild parrots are largely unknown. Additionally, recent research suggests there is a diverse range of novel Chlamydiales circulating in wildlife. We therefore sampled seven abundant parrot species in south-eastern Australia, taking cloacal swabs and serum from n = 132 wild adults. We determined C. psittaci and Chlamydiales prevalence and seroprevalence, and tested for host species, sex, geographical and seasonal differences, and temporal changes in individual infection status. Across all species, Chlamydiales prevalence was 39.8% (95% CI 31.6, 48.7), C. psittaci prevalence was 9.8% (95% CI 5.7, 16.3) and C. gallinacea prevalence was 0.8% (95% CI 0.1, 4.5). Other Chlamydiales species were not identified to species level. We identified two C. psittaci strains within the 6BC clade, which is highly virulent in humans. Seroprevalence was 37.0% (95% CI 28.5, 46.4). Host species (including crimson rosellas, galahs, sulphur-crested cockatoos and blue-winged parrots) differed in seroprevalence and Chlamydiales prevalence. Galahs had both highest Chlamydiales prevalence (54.8%) and seroprevalence (74.1%). Seroprevalence differed between sites, with a larger difference in males (range 20–63%) than females (29–44%). We reveal a higher chlamydial prevalence than previously reported in many wild parrots, with implications for potential reservoirs, and transmission risks to humans and other avian hosts.

Spatial and temporal patterns of lateralization in a parrot species complex

Cerebral lateralization involves information being processed differently by the brain’s two hemispheres and is often associated with behavioural laterality such as preferential use of right or left limbs. Despite having evolved widely in animals, laterality of limb use has been mostly studied in humans and other primates (e.g. handedness) and is relatively poorly understood in other taxa. Perhaps accordingly, the possibility of geographic variation in laterality has been largely overlooked. Foot preferences in parrots have been established as a tractable model for behavioural laterality investigations. Here we tested for geographic and temporal variation in lateralization of foot use in an Australian parrot complex, the crimson rosella (Platycercus elegans). We observed lateralization of foot use during foraging in N = 458 wild individuals over nine years, from 42 locations and four subspecies. We show, for the first time to our knowledge in any animal, a cline in laterality. In the morphologically highly variable P. e. adelaidae subspecies, which occupies a marked latitudinal habitat cline, we show that right side lateralization increased at higher (more southerly) latitudes. We also found ambidexterity varied between subspecies, and was present almost exclusively in the morphologically intermediate populations which occupy intermediate habitats, reaching 11% of individuals in one such population. Across all populations, strong lateralization at individual and population levels existed, with 93% of birds consistently lateralized, and 64% using the right foot preferentially. Age, year, season, or whether the bird was perched or on the ground, had no effects on foot preference. Using captive birds, we show that foot preferences were largely stable within individuals over time. Our findings provide rare examples of an intraspecific cline in behavioural lateralization and population differences in ambidexterity, and provide novel support for the hypothesis that ecological factors such as habitat and/or diet influences behavioural laterality within free-living animals.

Chlamydial diversity and predictors of infection in a wild Australian parrot, the Crimson Rosella ( Platycercus elegans )

Members of the Chlamydia genus are known to cause disease in both humans and animals. A variety of other species in the order Chlamydiales are increasingly being discovered and emerging as potential pathogens, yet there are scarce data on the diversity, prevalence and impacts of these pathogens in wild birds. To address this gap, we investigated which Chlamydiales species are present in a wild population of a common Australian parrot, the Crimson Rosella (Platycercus elegans). We collected cloacal swabs and serum from 136 individuals in south-eastern Australia, over two years, and tested several predictors of prevalence: age, sex, season and breeding status. We used multiple PCR assays to determine bacterial prevalence in cloacal swabs and a solid-phase ELISA to determine seroprevalence. We found Chlamydiales PCR prevalence of 27.7% (95% CI 20.2, 36.2) and identified at least two families (Chlamydiaceae and Parachlamydiaceae). Regarding known chlamydial avian pathogens, we found C.psittaci at 6.2% (95% CI 2.7, 11.8) and C.gallinacea at 4.6% (95% CI 1.7, 9.8) prevalence. We also identified at least two potentially novel Chlamydiales species, of unknown pathogenicity. Sex and breeding status predicted Chlamydiales PCR prevalence, with females more likely to be infected than males, and non-breeding birds more likely to be infected than breeding birds. Seroprevalence was 16% (95% CI 8.8, 25.9). Season and breeding status were strong predictors of seroprevalence, with highest seroprevalence in autumn and in non-breeding birds. Our results reveal a diversity of Chlamydiales species in this abundant wild host, and indicate that host-specific and temporal factors are associated with infection risk. Our findings suggest that wild parrots are a reservoir of both known and novel Chlamydiales lineages, of zoonotic and pathogenic potential.

Beak and feather disease virus (BFDV) prevalence, load and excretion in seven species of wild caught common Australian parrots.

Pathogens pose a major risk to wild host populations, especially in the face of ongoing biodiversity declines. Beak and feather disease virus (BFDV) can affect most if not all members of one of the largest and most threatened bird orders world-wide, the Psittaciformes. Signs of disease can be severe and mortality rates high. Its broad host range makes it a risk to threatened species in particular, because infection can occur via spill-over from abundant hosts. Despite these risks, surveillance of BFDV in locally abundant wild host species has been lacking. We used qPCR and haemagglutination assays to investigate BFDV prevalence, load and shedding in seven abundant host species in the wild in south-east Australia: Crimson Rosellas (Platycercus elegans), Eastern Rosellas (Platycercus eximius), Galahs (Eolophus roseicapillus), Sulphur-crested Cockatoos (Cacatua galerita), Blue-winged Parrots (Neophema chrysostoma), Rainbow Lorikeets (Trichoglossus moluccanus) and Red-rumped Parrots (Psephotus haematonotus). We found BFDV infection in clinically normal birds in six of the seven species sampled. We focused our analysis on the four most commonly caught species, namely Crimson Rosellas (BFDV prevalence in blood samples: 41.8%), Sulphur-crested Cockatoos (20.0%), Blue-winged Parrots (11.8%) and Galahs (8.8%). Species, but not sex, was a significant predictor for BFDV prevalence and load. 56.1% of BFDV positive individuals were excreting BFDV antigen into their feathers, indicative of active viral replication with shedding. Being BFDV positive in blood samples predicted shedding in Crimson Rosellas. Our study confirms that BFDV is endemic in our study region, and can inform targeted disease management by providing comparative data on interspecies variation in virus prevalence, load and shedding.

A non-invasive method to assess environmental contamination with avian pathogens: beak and feather disease virus (BFDV) detection in nest boxes.

Indirect transmission of pathogens can pose major risks to wildlife, yet the presence and persistence of wildlife pathogens in the environment has been little studied. Beak and feather disease virus (BFDV) is of global conservation concern: it can infect all members of the Psittaciformes, one of the most threatened bird orders, with infection often being lethal. Indirect transmission of BFDV through contaminated nest hollows has been proposed as a major infection source. However, data on whether and for how long nest sites in the wild remain contaminated have been absent. We determined the BFDV status of birds (parents and nestlings) for 82 nests of Crimson Rosellas, Platycercus elegans and Eastern Rosellas, Platycercus eximius. In 11 of these nests (13.4%, 95% confidence interval 6.9–22.7), we found an infected parent or nestling. Using nest swabs, we then compared BFDV presence at three points in time (before, during and after breeding) in three groups of nest boxes. These were nest boxes occupied by infected birds, and two control groups (nest boxes occupied by uninfected birds, and unoccupied nest boxes). Detection of BFDV on nest swabs was strongly associated with the infection status of parents in each nest box and with the timing of breeding. During breeding, boxes occupied by BFDV-positive birds were significantly more likely to have BFDV-positive nest swabs than boxes occupied by BFDV-negative birds; nest swabs tested BFDV-positive in 80% (28.4–99.5) of nests with parental antigen excretion, 66.7% (9.4–99.2) of nests occupied by parents with BFDV-positive cloacal swabs and 66.7% (22.3–95.7) of nests occupied by parents with BFDV–positive blood. 0% (0–52.2) of nests with BFDV–positive nestlings had BFDV–positive nest swabs. Across all boxes occupied by BFDV-positive birds (parents or nestlings), no nest swabs were BFDV–positive before breeding, 36.4% (95% CI 10.9–69.2) were positive during breeding and 9.1% (0.2–41.3) remained positive after breeding. BFDV was present on nest swabs for up to 3.7 months. Our study provides novel insights into the potential role of nest cavities and other fomites in indirect transmission of BFDV, and possibly other pathogens, and offers a non-invasive method for surveillance of pathogens in wild bird populations.

Seasonal fluctuation of beak and feather disease virus (BFDV) infection in wild Crimson Rosellas (Platycercus elegans)

Understanding patterns of pathogen emergence can help identify mechanisms involved in transmission dynamics. Beak and feather disease virus (BFDV) poses a major threat world-wide to wild and captive parrots. Yet data from wild birds on seasonal fluctuations in prevalence and infection intensity, and thereby the potential high-risk times for virus transmission, have been lacking. We screened wild Crimson Rosellas (Platycercus elegans) for BFDV in blood and cloacal swabs. Prevalence in blood samples and cloacal swabs, as well as viral load varied with Julian date and in blood, were highest after the breeding season. Breeding birds had lower viral load and lower BFDV prevalence in blood than non-breeding birds (10.1% prevalence in breeding vs. 43.2% in non-breeding birds). BFDV prevalence was much higher in younger (<3 years) than older (≥3 years) birds for both blood samples (42.9% vs. 4.5%) and cloacal swabs (56.4% vs. 12.3%). BFDV status in blood and cloacal samples was not correlated within individuals. We show that, at least in P. elegans, BFDV infection seems to occur year-round, with seasonal changes in prevalence and load found in our samples. Our analyses suggest that the seasonal changes were associated primarily with the breeding season. We also discuss age and sex as important predictors of BFDV infection.

Persistence of beak and feather disease virus (BFDV) infection in wild Crimson Rosellas (Platycercus elegans)

ABSTRACTBeak and feather disease virus (BFDV) is a globally distributed pathogen of psittacine birds. In Australia, it is thought to be the dominant pathogen of Psittaciformes, and it is listed as a ‘key threatening process to biodiversity’. Infection with BFDV can cause serious and often fatal disease. However, knowledge on BFDV infection persistence in wild hosts is scarce. We investigated this in 55 wild Crimson Rosellas (Platycercus elegans) in Victoria, Australia, which were trapped and tested two to five times during 14 years of study. We analysed blood and feather samples for BFDV and antibodies. We then quantified infection persistence in 17 individuals that were BFDV-positive (BFDV+) during at least one capture, and that were recaptured at intervals of 0.5 months to 5.9 years. Birds that were BFDV+ when first caught were likely to also be BFDV+ if recaptured within the following five months (80%, 4/5), but this rate declined to only 8.3% of birds (1/12) that were recaptured more than five months after initial capture. BFDV was detected in feathers of 44.4% (4/9) of birds that were BFDV+ in blood upon initial capture, and 88.9% (8/9) of these individuals showed an immunological response to infection upon recapture. Viral load varied between captures and individuals. Our data indicate that P. elegans can clear BFDV from their blood, and provide new estimates for the duration of chronic BFDV infection in wild parrots. These findings can aid wildlife disease management and species conservation.

Do glucocorticoids or carotenoids mediate plumage coloration in parrots? An experiment in Platycercus elegans

Conspicuous coloration can indicate phenotypic quality, and may reflect exposure or vulnerability to stress, or access to essential nutrients such as pigments. Although the production of pigmented colours is well understood, much less is known about how structural colours are affected by physiological state. In this study, we tested whether glucocorticoids (corticosterone) predicted expression of plumage coloration in an Australian parrot, the crimson rosella (Platycercus elegans). Parrots provide an interesting and unique test, as they possess conspicuous coloration produced by distinctive pigments known as psittacofulvins, in addition to structural coloration. We have previously documented that coloration in P. elegans is condition-dependent and responds to dietary manipulation. Here, n = 21 P. elegans underwent a dietary manipulation (including food restriction or carotenoid supplementation) during which they moulted, and the change in reflectance was measured for three structural and three pigmentary plumage patches. Stress-induced corticosterone (10 min after handling) measured at the start of the experiment predicted change in coloration in two pigmentary patches (crown and front). We also found that change in stress-induced corticosterone during the experiment was associated with the change in coloration of the crown and two structural patches (cheek and epaulette). Baseline corticosterone (<3 min after handling) was not associated with any measure of coloration. We found no effects of dietary manipulation on baseline or stress-induced corticosterone, but carotenoid supplementation was associated with an increase in a measure of chronic stress (heterophil/lymphocyte ratio), and the corticosterone response to handling decreased over the course of the study. Our results suggest that corticosterone may be linked to colour expression more broadly than previously recognised, including psittacofulvin and structural coloration in parrots, and they confirm the independence of plumage pigmentation in parrots from carotenoid accumulation. Moreover, our study provides new insight into the stress responses of Psittaciformes, one of the most highly threatened avian orders.

Plumage coloration follows Gloger's rule in a ring species

AbstractAimAnimal coloration is expected to differ between populations in different habitats according to Gloger's rule, with darker animals found in more humid, vegetated or warmer environments. Yet despite considerable support across the globe, the mechanisms behind this biogeographical rule are currently still unclear. Exploiting a ring species with plumage coloration from crimson to pale yellow, we test Gloger's rule and the mechanisms behind phenotypic divergence.LocationSouth‐eastern Australia.Major taxa studiedCrimson rosellas (Platycercus elegans).MethodsWe combined three modelling approaches (spatial regression; random decision forest species distribution and conditional inference tree) to test the association between 10 environmental variables (based on long‐term climate data and remotely sensed reflectance of the land) and plumage coloration across the distribution of P. elegans. We also took in‐situ measurements of background coloration of dominant vegetation to examine the relationship between (a) background coloration measured locally and remotely, (b) P. elegans coloration and (c) known differences in visual sensitivity of the subspecies using species‐specific visual models.ResultsOn both a continental and a local scale, the distribution of yellow‐red plumage coloration was strongly predicted by average rainfall, summer temperature and the Earth's reflectance between 620–670 nm. Remotely sensed radiance measures correlated strongly and positively with reflectance of the leaves of the dominant tree species at sites across the P. elegans distribution. Visual modelling indicated that differences in background colour could affect signalling efficacy in dim‐light conditions.Main conclusionsOur study shows that the highly variable plumage coloration conforms to Gloger's rule, and indicates that background coloration of the vegetation and thermoregulation are likely to be important mechanisms. Our results also show that Gloger's rule can explain variation in pigmentary systems other than melanin, and highlight that selection from environmental variation could be an important force behind the geographic diversity found in ring species.

Prevalence of BFDV in wild breeding Platycercus elegans

Pathogens can have a profound impact on the population dynamics of avian populations. Beak and feather disease virus (BFDV) is considered one of the few pathogens capable of causing extinction, because it predominantly infects the highly threatened order Psittaciformes, the signs of disease are severe, and mortality can be extremely high. Little is known about BFDV in wild populations, particularly its distribution among wild breeding birds. We investigated patterns of BFDV infection in family groups across three different subspecies of a common southeast Australian parrot (Platycercus elegans). We predicted that due to the high degree of contact, shared environment and high relatedness within family units, the prevalence of infection would be uniform. However, we found more non-infected breeding pairs than expected if there was random mating, whilst cases where both pair members were infected were observed less often than expected under random mating. When one pair member was infected, it was sex-biased, with males rarely infected. We found that parental infection status did not explain nestling infection status, suggesting that other infection routes (e.g. from the hollow or nest material) are likely. Future work is needed to assess transmission and behavioural mechanisms that explain patterns of infection among breeding birds.

Heterospecific competition in a threatened cavity-nesting parrot: a case study of the eastern Regent Parrot (Polytelis anthopeplus monarchoides)

ABSTRACTNest cavities are a limited resource, given the extensive land clearance that has occurred in Australia. Some obligate cavity-nesting birds are vulnerable to extinction and experience risk from heterospecific species that compete for limited nest cavities. The aim of this study was to identify intruder bird species at nest cavities of a threatened eastern subspecies of Regent Parrot (Polytelis anthopeplus monarchoides), and to measure the impact of intruder birds on parental care (parental time budgets) and nesting outcome (nest usurpation). We observed 25 eastern Regent Parrot nests using a combination of 608 h of video recording and 67 h of binocular observation. In total, we observed 16 heterospecific bird species at the nest entrance of the eastern Regent Parrot. Two of these species were examined for their impact on parental care behaviour. The presence of Noisy Miners (Manorina melanocephala) near the nest cavity increased the time that Regent Parrots spent at the nest cavity entrance. The number of Yellow Rosella (Platycercus elegans flaveolus) visits to the nest cavity predicted nest usurpation. Nest usurpation of a Regent Parrot nest occurred in 6/25 cases (24%), of which 5/6 nests were usurped by Yellow Rosellas. Understanding heterospecific competition for nest cavities in eastern Regent Parrots should inform targeted conservation measures.

Nest microclimate predicts bill growth in the Adelaide rosella (Aves: Psittaculidae)

Diet and foraging have traditionally been considered key drivers of bill morphology. It is now known that bills play an important thermoregulatory role, and recent studies revealed that temperature is positively associated with the size of bills relative to body size or weight in adult birds, in accordance with Allen’s rule. Studies have attributed these patterns to local adaptation or an evolutionary response to climate change, but the contribution of ontogenetic plasticity remains unclear. We tested whether temperature experienced inside the nest predicted nestling growth in bill size and weight and in a parrot, the Adelaide rosella (Platycercus elegans adelaidae). We predicted that nest microclimate may affect bill ontogeny, leading to a positive association between relative bill size and temperatures during rearing. Growth in bill surface area was greater in nests that were warmer during the day and night, but temperature variability had no effect. Higher day and night-time mean temperatures, and less variable night-time temperatures, were positively associated with nestling weight. Our findings indicate that nest microclimate influences nestling growth, including relative bill size, and that daytime heat dissipation may be a driver of bill ontogeny. Bill plasticity in response to temperature during rearing could be an important but little studied contributor to morphology, due to the role of the bill in thermoregulation.