Galahs Research Articles

Tibiotarsal Subcutaneous Xanthogranuloma in a Rose-breasted Cockatoo (Eolophus roseicapilla): A Case Report

Background: Xanthogranuloma (xanthoma) presents as a rare, non-infectious granulomatous lesion with a yellowish and soft appearance. Hypercholesterolemia and hyperlipidemia are believed to be the underlying causes of this lesion. Xanthoma has been identified in vertebrates and humans. Objectives: This report presents a case of cutaneous xanthogranuloma located in the tibiotarsal region of a 5-year-old rose-breasted cockatoo (Eolophus roseicapilla) fed with high-fat diets. Methods: The cockatoo underwent anesthesia using isoflurane administered through a face mask connected to an Ohmeda anesthesia machine. The mass was surgically removed and submitted for histopathological examination. The tissue was fixed in 10% neutral buffered formalin, and representative sections were routinely processed for hematoxylin and eosin (H&E) staining. Moreover, frozen sections were obtained and stained with the Oil Red O technique. Results: Upon histopathologic examination of routine H&E slides, vacuolated macrophages, and multinucleated giant cells were noted in addition to cholesterol clefts and heterophilic infiltrates. Oil Red O staining was performed to detect intracellular and extracellular lipid content. Xanthogranulomas invaded the surrounding tissues, necessitating complete surgical excision. The lesion did not recur during the 1-month follow-up, but the patient died due to respiratory disorders. Conclusion: Stress and high-lipid feed consumption were considered the predisposing factors to xanthogranuloma development in this bird.

Radiographic Measurements of the Cardiac Silhouette and Comparison with Other Radiographic Landmarks in Wild Galahs (Eolophus roseicapilla).

Simple SummaryCardiac diseases are a common finding in captive parrots. In this retrospective study, the cardiac silhouette of 36 wild galahs was measured in the ventrodorsal and laterolateral projections using radiographic images. The aim of the study was to determine reference values of the width and the length of the heart of wild galahs in relation to other anatomic landmarks. The evaluated reference indicates that the width of the heart is 50–65% of the thoracic width and 570–743% of the coracoid width.Background: Part of the diagnostic workup for cardiac diseases is radiographic imaging. To determine an enlarged heart, species-specific reference values are necessary. Wild birds are rarely diagnosed with cardiac disease, and only a few studies have been done to investigate the cardiac silhouette in wild birds. Methods: In this retrospective study, the cardiac silhouette of 36 wild galahs, presented at the hospital, was investigated in relation to other anatomic landmarks like the thoracic width, clavicula width, synsacrum width, distance between the third and fourth rib, distance of the clavicula, and length and height of the sternum using a digital DICOM viewer. Results: The cardiac width was significant compared to the thoracic width with a minimum to maximum of 50 to 65%. The cardiac width compared with the coracoid width also showed significant results with a minimum to maximum range of 570 to 743%. A significant correlation was found between the weight and the cardiac width and length. Conclusion: The cardiac silhouette in wild galahs is easily measured in both radiographic views, and the heart size can be compared to other anatomical landmarks.

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.

Opportunistic sampling of wild native and invasive birds reveals a rich diversity of adenoviruses in Australia.

Little is known about the diversity of adenoviruses in wild birds and how they have evolved and are maintained in complex ecosystems. In this study, 409 samples were collected from woodland birds caught for banding (droppings), birds submitted to a wildlife hospital (droppings and tissues), silver gulls (droppings or tissues), and feral pigeons (Columbia livia; oral, cloacal swabs, or tissues) from the Greater Sydney area in NSW, Australia. Additional samples were from native pigeons and doves (swabs) presented to the Healesville Sanctuary, VIC, Australia. Samples were screened for adenovirus DNA using degenerate primers and polymerase chain reaction. Adenovirus sequences were detected in eighty-three samples representing thirty-five novel amino acid sequences. Fourteen novel sequences were atadenoviruses, seven were aviadenoviruses, twelve were siadenoviruses, and one was a mastadenovirus. Sequences from passerine birds were predominately found to form a single lineage within the atadenoviruses, a second lineage in the siadenoviruses, and a third smaller aviadenovirus lineage. These viruses appeared to have co-evolved with a diverse group of woodland birds that share similar habitat. Evidence for host/virus co-evolution in some viruses and a wide host range in others was observed. A high prevalence of adenovirus infection was found in rainbow lorikeets (Trichoglossus haematodus), galahs (Eolophus roseicapilla), and sulphur-crested cockatoos (Cacatua galerita). Sequences were either identical to or mapped to already established lineages in the Aviadenovirus, Siadenovirus, and Atadenovirus genera, suggesting a possible origin of the psittacine adenoviruses in ancestral Australian psittacine birds. The sequences of passerine and psittacine origin provided insight into diversity and structure of the Atadenovirus genus and demonstrated for the first-time viruses of passerine origin in the Aviadenovirus genus. Four unrelated adenovirus sequences were found in silver gull samples (Chroicocephalus novaehollandiae), including one of pigeon origin, suggesting environmental virus exposure. Three pigeon adenovirus types were detected in feral pigeons and infection prevalence was high. Evidence for host switching between invasive species and native species and native species and invasive species was documented. A variant of a murine adenovirus was detected in kidney tissue from two bird species suggesting mouse to bird transmission.

Herb endozoochory by cockatoos: Is ‘foliage the fruit’?

AbstractEstablishing whether herb seed endozoochory is accidental or has evolved independently or in combination with other dispersal mechanisms may be valuable in the study of plant–animal interactions, but it remains unexplored for birds. We tested whether an Australian cockatoo, the galah (Eolophus roseicapilla), swallows entire seeds when feeding on other tissues without subsequent seed digestion, thus enhancing seed dispersal (the ‘foliage is the fruit’ hypothesis). Our preliminary sampling provides strong evidence supporting that this seed predator also acts as a legitimate endozoochorous disperser. A large proportion of droppings contained numerous seeds of six herb species of three plant families, surviving gut passage to be dispersed as viable propagules. The wide range in the number of seeds found in combinations with up to five species in particular droppings suggests both simultaneous and sequential passive ingestion without seed digestion and/or focused seed predation and digestion. As expected for inadvertent ingestion and inefficient digestion, our findings suggest that seed number and richness of dispersed plants are associated traits in this particular mutualistic interaction. This relationship can have important implications in community‐wide processes, favouring herbs whose seeds are disseminated in a viable state over those predated or negatively affected by gut transit.

Investigation and treatment of lead toxicity in a galah (Eolophus roseicapilla)

Birds can be exposed to oral toxins either inside or outside of their main enclosures. The psittacine beak is adapted not only for grasping and processing food but also for climbing, therefore toxin exposure can be either deliberate (by active ingestion), or accidental. A 1-year-old male galah (Eolophus roseicapilla) was presented with a 4-day history of neurological signs including loss of balance and seizures. The bird had access to a garage and was thought to have been chewing on lead sheeting. Radiodense particles were identified in the ventriculus and high lead levels were confirmed on toxicology. Treatment was instigated with calcium disodium edetate and a full recovery was made. This case study details the investigation and treatment for a typical presentation of lead poisoning in a psittacine.

Additions to prey taken by Wedge-tailed Eagles Aquila audax after release of Rabbit Oryctolagus cuniculus haemorrhagic disease (Rabbit Calicivirus) in 1996

Identifications of five species of birds considered prey of Wedge-tailed Eagles Aquila audax following the 1996 release of Rabbit Oryctolagus cuniculus haemorrhagic disease (Rabbit Calicivirus) in western New South Wales are given. The following taxa were identified from their sterna in Wedge-tailed Eagle nests: Sulphur-crested Cockatoo Cacatua galerita , Galah Eolophus roseicapilla , Australian Magpie Gymnorhina tibicen , Little Crow Corvus bennetti and Plains-wanderer Pedionomus torquatus .

Parrots evaporate water to keep cool in sizzling temperatures

![Figure][1] A mulga parrot ( Psephotellus varius ; left) and a galah ( Eolophus roseicapilla ; right). Photo credits: Matt Baumann (left) and William Talbot (right). The title of ‘The hottest place on Earth’ is keenly debated. Some experts have cast doubt on the reliability of Death

Avian thermoregulation in the heat: evaporative cooling capacity and thermal tolerance in two Australian parrots.

Avian orders differ in their thermoregulatory capabilities and tolerance of high environmental temperatures. Evaporative heat loss, and the primary avenue whereby it occurs, differs amongst taxa. Although Australian parrots (Psittaciformes) have been impacted by mass mortality events associated with extreme weather events (heat waves), their thermoregulatory physiology has not been well characterized. We quantified the upper limits to thermoregulation under extremely hot conditions in two Australian parrots: the mulga parrot (Psephotellus varius; ∼55 g) and the galah (Eolophus roseicapilla; ∼265 g). At air temperatures (Ta) exceeding body temperature (Tb), both species showed increases in Tb to maximum values around 43-44°C, accompanied by rapid increases in resting metabolic rate above clearly defined upper critical limits of thermoneutrality and increases in evaporative water loss to levels equivalent to 700-1000% of baseline rates at thermoneutral Ta Maximum cooling capacity, quantified as the fraction of metabolic heat production dissipated evaporatively, ranged from 1.71 to 1.79, consistent with the known range for parrots, similar to the corresponding range in passerines, and well below the corresponding ranges for columbids and caprimulgids. Heat tolerance limit (the maximum Ta tolerated) ranged from 44 to 55°C, similar to the range reported for passerines, but lower than that reported for columbids and caprimulgids. Our data suggest that heat tolerance in parrots is similar to that in passerines. We argue that understanding how thermoregulatory capacity and heat tolerance vary across avian orders is vital for predicting how climate change and the associated increase in frequency of extreme weather events may impact avian populations in the future.

Ancient DNA resolves the subspecific identity of the holotype of the Galah Eolophus roseicapilla, a widespread Australian cockatoo

Conventional thinking for many years held that the holotype of the Galah Eolophus roseicapilla, obtained in 1801 by the Baudin Expedition from France, was from south-eastern Australia. This did not mesh well with what is known of Galahs not having occurred in that part of Australia at that time. That it must have been a western bird is now strongly supported by bibliographic and morphological evidence. Our earlier phylogeographic study of the Galah had shown geographical structure in its mitochondrial DNA (mtDNA). We reasoned that if mtDNA could be extracted from the holotype the matter should be resolvable. We report the results of this work and affirm the case made from morphological and bibliographic data.

East or west: to which subspecies does the type specimen of the Galah, Eolophus roseicapilla (Vieillot, 1817) (Aves: Cacatuidae), belong?

The Galah (Eolophus roseicapilla) is a pink-and-grey cockatoo, widespread in and endemic to Australia, and now familiar as a cage bird world-wide. It has three currently recognised subspecies: roseicapilla Vieillot, 1817 in the Australian west, kuhli Mathews, 1912 in the far north, and albiceps Schodde, 1989 in the east (Schodde 1997; Higgins 1999; Dickinson & Remsen 2013; del Hoyo & Collar 2014; Engelhard et al. 2015). The northern subspecies, kuhli, is not involved in the issue of type identity of roseicapilla, and so is not considered further here. First to distinguish east and west subspecies was G.M. Mathews (1912). Without explanation then or later, Mathews arbitrarily applied the senior specific name, Cacatua roseicapilla Vieillot, 1817 and its two objective synonyms based on the same type-eos Kuhl, 1820 and rosea Vieillot, 1822-to the eastern subspecies, and introduced the new name assimilis for the then supposedly undescribed western form. Mathews' lead was followed unquestioningly until the late 1980s when Schodde (1989) and Rowley (1990: 3) concluded that the type of Vieillot's roseicapilla was of the western subspecies, collected by the Baudin expedition in the region of Shark Bay on the mid-western Australian coast. Rowley (l.c.), but not Schodde (l.c.) contrary to Rowley's reference, went further to claim that it had been taken by François Péron in 1803, presumably on the brief return visit of Baudin in Le Géographe to Shark Bay en route to France. This left the eastern subspecies un-named, which Schodde (l.c.) accordingly described as albiceps.

Rise (and demise?) of subspecies in the Galah (Eolophus roseicapilla), a widespread and abundant Australian cockatoo

The Galah (Eolophus roseicapilla) is a widespread Australian bird. Its geographical variation and subspecies remain poorly understood. We sampled 192 specimens from across the entire range of the species to assess its phylogeographical structure using the mitochondrially encoded NADH dehydrogenase 2 (MT-ND2) gene. A subset of specimens was examined for nuclear DNA diversity using the Amplified Fragment Length Polymorphism (AFLP) method. Weakly defined structure was evident in the mitochondrial DNA (mtDNA) data, which suggested three geographically defined haplogroups that broadly coincide with the three conventionally recognised subspecies: E. r. roseicapilla—western haplogroup; E. r. albiceps—eastern haplogroup; and E. r. kuhli—northern haplogroup. The three haplogroups all overlap and intersect broadly across the centre of the Australian continent. Geographical expansions of each haplogroup appear to have occurred before and after the Last Glacial Maximum (~20 000 years ago), the species itself probably having undergone an earlier expansion at c. 60 000 years ago. The preliminary nuclear AFLP data suggest very little structure though they likely track more recent processes of gene flow and population admixture. Expansion of the species since European settlement represents another, later expansion uncoupled from what is tracked in the mtDNA data. Future quantitative analyses of phenotypic variation will enhance the precision of how geographical variation in all datasets in this species should be interpreted.

Pathologic-anatomic and morphometric examinations on the heart in feral cockatoos

To evaluate the heart of free-living psittacine birds macroscopically and morphologically, and to compare the results to findings published for psittacine birds living in captivity to obtain information on the influence of bird keeping in a human environment on the psittacine heart. In total, 84 wild-living cockatoos were examined, including 50 sulphur-crested cockatoos (Cacatua galerita), 31 galahs (Eolophus roseicapilla) and three long-billed corellas (Cacatua tenuirostris). The birds were euthanized because of a local cockatoo control program in Australia, and were examined pathologically within 8 hours of euthanasia. A macroscopic necropsy was performed, and the heart was assessed morphologically. Furthermore, a histological organ screening was conducted. The birds demonstrated good body condition and excellent muscle condition. Except for some paleness of the heart muscle, none of the animals showed any pathological alteration of the heart or large vessels. The mean heart mass was 8.7 g for the sulphur-crested cockatoos, 5.3 g for the galahs and 8.6 g for the long-billed corellas. Independent of the species examined, a highly significant correlation was found between the heart and body masses (r = 0.91; p < 0.001), which was also confirmed as significant within the sulphur-crested cockatoo (r = 0.59; p < 0.001) and galah groups (r = 0.52; p = 0.003). This correlation can be used to calculate the expected heart mass based on the body mass, using the formula: heart mass (g) = 2.9 + 0.01 x body mass (g). In comparison to reports on Australian parakeets, the relative thickness of the heart muscle wall of the left ventricle found in this study was greater. In comparison to psittacine birds kept in captivity, wild-living cockatoos have good body condition and rarely suffer from macroscopically detectable diseases of the heart or large vessels. The cardiac fitness level is superior in comparison to that found in healthy appearing psittacine birds kept in captivity. The results can serve as a basis for the assessment of the heart in psittacine birds, because in contrast to earlier reports, the heart of healthy psittacine birds not previously exposed to any human influence could be assessed.

Patterned-String Tasks: Relation between Fine Motor Skills and Visual-Spatial Abilities in Parrots

String-pulling and patterned-string tasks are often used to analyse perceptual and cognitive abilities in animals. In addition, the paradigm can be used to test the interrelation between visual-spatial and motor performance. Two Australian parrot species, the galah (Eolophus roseicapilla) and the cockatiel (Nymphicus hollandicus), forage on the ground, but only the galah uses its feet to manipulate food. I used a set of string pulling and patterned-string tasks to test whether usage of the feet during foraging is a prerequisite for solving the vertical string pulling problem. Indeed, the two species used techniques that clearly differed in the extent of beak-foot coordination but did not differ in terms of their success in solving the string pulling task. However, when the visual-spatial skills of the subjects were tested, the galahs outperformed the cockatiels. This supports the hypothesis that the fine motor skills needed for advanced beak-foot coordination may be interrelated with certain visual-spatial abilities needed for solving patterned-string tasks. This pattern was also found within each of the two species on the individual level: higher motor abilities positively correlated with performance in patterned-string tasks. This is the first evidence of an interrelation between visual-spatial and motor abilities in non-mammalian animals.

The evolutionary history of cockatoos (Aves: Psittaciformes: Cacatuidae)

Cockatoos are the distinctive family Cacatuidae, a major lineage of the order of parrots (Psittaciformes) and distributed throughout the Australasian region of the world. However, the evolutionary history of cockatoos is not well understood. We investigated the phylogeny of cockatoos based on three mitochondrial and three nuclear DNA genes obtained from 16 of 21 species of Cacatuidae. In addition, five novel mitochondrial genomes were used to estimate time of divergence and our estimates indicate Cacatuidae diverged from Psittacidae approximately 40.7million years ago (95% CI 51.6–30.3Ma) during the Eocene. Our data shows Cacatuidae began to diversify approximately 27.9Ma (95% CI 38.1–18.3Ma) during the Oligocene. The early to middle Miocene (20–10Ma) was a significant period in the evolution of modern Australian environments and vegetation, in which a transformation from mainly mesic to xeric habitats (e.g., fire-adapted sclerophyll vegetation and grasslands) occurred. We hypothesize that this environmental transformation was a driving force behind the diversification of cockatoos. A detailed multi-locus molecular phylogeny enabled us to resolve the phylogenetic placements of the Palm Cockatoo (Probosciger aterrimus), Galah (Eolophus roseicapillus), Gang-gang Cockatoo (Callocephalon fimbriatum) and Cockatiel (Nymphicus hollandicus), which have historically been difficult to place within Cacatuidae. When the molecular evidence is analysed in concert with morphology, it is clear that many of the cockatoo species’ diagnostic phenotypic traits such as plumage colour, body size, wing shape and bill morphology have evolved in parallel or convergently across lineages.

Molecular Genetic and Pathogenic Characterization of Psittacid Herpesvirus Type 1 Isolated from a Captive Galah (Eolophus roseicapillus) in Japan

Psittacid herpesvirus type 1 (PsHV-1) was isolated from a captive galah (Eolophus roseicapillus) in Japan that was suspected of having Pacheco's disease (PD), an acute fatal disease in psittacine birds. PsHV-1 has been classified into four genotypes based on the UL16 gene sequence. In the present study, we investigated the genetic and pathogenic characteristics of the isolated virus, FOY-1, compared with a reference strain, RSL-1. The FOY-1 strain was classified into PsHV-1 genotype 2. The FOY-1 strain was found to be less pathogenic to budgerigars than RSL-1, which was classified as genotype 4 in an in vivo study. This is the first report regarding the classification of originally isolated PsHV-1 in Japan and its characterization by animal infection experiment.

Health and Nutritional Status of Wild Australian Psittacine Birds: An Evaluation of Plasma and Hepatic Mineral Levels, Plasma Biochemical Values, and Fecal Microflora

To evaluate the health and nutritional status of 3 wild Australian psittacine species, plasma and hepatic mineral concentrations and plasma biochemical values were measured in wild-caught galahs (Eolophus roseicapilla), long-billed corellas (Cacatua tenuirostris), and sulphur-crested cockatoos (Cacatua galerita). No correlations were found between hepatic and plasma mineral levels. Mean plasma calcium (1.79 mmol/L [7.16 mg/dL]) and sodium (103 mmol/ L [103 mEq/L]) concentrations were lower, whereas mean total phosphorus (6.53 mmol/L [20.22 mg/dL]) and potassium (8.87 mmol/L [8.87 mEq/L]) concentrations were higher than values for captive counterparts. Plasma iron levels were higher than those reported for captive counterparts, with evidence of interspecific (sulphur-crested cockatoos, 109 micromol/L [609 microg/dL]; corellas, 57 micromol/L [318 microg/dL]; galahs, 90 micromol/L [503 microg/dL]) and temporal variation (galahs: May, 107 micromol/L [598 microg/dL]; July, 59 micromol/L [330 microg/dL]). Hepatic iron concentrations were as high as 1030 mg/kg. Interspecific variation was minimal in mean plasma selenium (11.8 micromol/L [929 microg/L]) and zinc (31.2 micromol/L [204 microg/dL]) concentrations. Plasma biochemical values varied significantly from reported reference ranges. Ranges for total protein, albumin, and bile acid concentrations were lower, whereas uric acid, glutamate dehydrogenase, amylase, and cholesterol concentrations were higher than those previously reported for these species, and interspecific variation was evident. Variation in measures of mineral status or plasma biochemical values between males and females were negligible. An evaluation of fecal microflora showed a distinct absence of gram-negative bacteria or budding yeast. Results of this study show that analyte values used to determine health and nutritional status of wild birds differ from those published for captive counterparts. Although analyte values appear to vary minimally by sex, distinct taxonomic and some temporal differences exist in values from wild birds of these 3 species.

Ian Cecil Robert Rowley 1926–2009

Ian Cecil Robert Rowley 1926–2009

Evidence for Adaptive Evolution of Olfactory Receptor Genes in 9 Bird Species

It has been suggested that positive selection, in particular selection favoring a change in the protein sequence, plays a role in the evolution of olfactory receptor (OR) gene repertoires in fish and mammals. ORs are 7-transmembrane domain (TM) proteins, members of the G-protein-coupled receptor superfamily in vertebrate genomes, and responsible for odorant binding and discrimination. OR gene repertoires in birds are surprisingly large and diverse, suggesting that birds have a keen olfactory sense. The aim of this study is to investigate signatures of positive selection in an expanded OR clade (group-gamma-c) that seems to be a characteristic of avian genomes. Using maximum-likelihood methods that estimate the d(N)/d(S) ratios and account for the effects of recombination, we show here that there is evidence for positive selection in group-gamma-c partial OR coding sequences of 9 bird species that are likely to have different olfactory abilities: the blue tit (Cyanistes caeruleus), the black coucal (Centropus grillii), the brown kiwi (Apteryx australis), the canary (Serinus canaria), the galah (Eolophus roseicapillus), the kakapo (Strigops habroptilus), the mallard (Anas platyrhynchos), the red jungle fowl (Gallus gallus), and the snow petrel (Pagodroma nivea). Positively selected codons were predominantly located in TMs, which in other vertebrates are involved in odorant binding. Our data suggest that 1) at least some avian OR genes have been subjected to adaptive evolution, 2) the extent of such adaptive evolution differs between bird species, and 3) positive selective pressures may have been stronger on the group-gamma-c OR genes of species that have well-developed olfactory abilities.

Male and female contact calls differentially influence behaviour in a cockatoo, the Galah (Eolophus roseicapillus)

Even in species in which males and females share a repertoire of calls, subtle sex differences in vocalisations often exist, particularly in calls used for long-distance communication. However, few studies address whether birds respond differently to similar male and female calls. This study investigated whether an Australian cockatoo, the Galah (Eolophus roseicapillus), responds differentially to three types of loud calls (Double Chet, Chechet and Chewp) commonly produced by both sexes. I played back male and female vocalisations to wild Galahs in Canberra, Australia, and recorded vocal and approach responses. Galahs responded differently to at least one call type, with birds approaching male Double Chets more closely but vocalising more to female Double Chets. Males were more likely than females to vocalise to Double Chets and Chechets, regardless of stimulus sex. These results suggest that males may have to expend more effort than females in forming affiliative relationships. Although males and females exhibited different vocal behaviour, paired males and females tended to approach stimuli together, which may indicate that coordination of movement, rather than coordination of vocal behaviour, is important in maintaining the pair-bond. These experiments show that even when the sexes share a repertoire, the sender and receiver sex may influence the nature of a vocal interaction.