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The ability to understand relational concepts, such as 'same' and 'different', is a critical feature of human cognition. To what extent non-human animals can acquire such concepts and which factors influence their learning are still unclear. We examined the acquisition and the breadth of understanding the 'same-different' concept in budgerigars ( Melopsittacus undulatus ). Budgerigars trained to discriminate stimulus pairs in which two identical figures were either the same or different size (Experiment 1) successfully generalized the discrimination to novel stimuli belonging to various categories (size, colour, shape, geometric type and number of dots). The results of Experiment 1 thus demonstrate that budgerigars can perceive and generalize the same-different concept across dimensions after training with a limited set of stimuli differing along a single dimension. In contrast, while most budgerigars trained to discriminate two pairs of discs that were either the same or different in colour (Experiment 2) could generalize the discrimination to novel stimuli within the training category (colour), only few generalized the discrimination to another category suggesting a generalization based on perceptual similarity. The results thus show that whether budgerigars generalize a relationship by conceptual or perceptual similarity depends on the nature of the training stimuli.

This clinical report describes an adult, female budgerigar ( Melopsittacus undulatus ) diagnosed with an ingluviolith. The patient presented for intermittent regurgitation, and a palpable foreign body was present in the crop. Radiographs showed a radiopaque foreign body, and computed tomography showed an approximately 16 × 12 mm (length 3 width) structure in the crop with a soft tissue and focally mineralized center and a 2-3 mm-thick mineral-attenuating shell. An ingluviotomy was performed. The stone was first analyzed using polarized optical crystallography, a method that cannot analyze uric acid salts, and was incorrectly deemed a cystine calculus. The calculus was then analyzed using infrared spectroscopy and x-ray diffractometry and was confirmed to be a shell of subcrystalline to monoclinic crystals of anhydrous uric acid (C 5 H 4 N 4 O 3 ) encrusting aggregates of numerous, threadlike, protein-based fibers. This case presents new information regarding avian ingluviolithiasis. The large size of the calculus indicates formation in the crop, and coprophagia linked to stress is thought to be the potential reason for urate and feather ingestion.

Background: Most vocal learning species exhibit an early critical period during which their vocal control neural circuitry facilitates the acquisition of new vocalizations. Some taxa, most notably humans and parrots, retain some degree of neurobehavioral plasticity throughout adulthood, but both the extent of this plasticity and the neurogenetic mechanisms underlying it remain unclear. Differential expression of the transcription factor FoxP2 in both songbird and parrot vocal control nuclei has been identified previously as a key pattern facilitating vocal learning. We hypothesize that the resilience of vocal learning to cognitive decline in open-ended learners will be reflected in an absence of age-related changes in neural FoxP2 expression. We tested this hypothesis in the budgerigar (Melopsittacus undulatus), a small gregarious parrot in which adults converge on shared call types in response to shifts in group membership. We formed novel flocks of 4 previously unfamiliar males belonging to the same age class, either "young adult" (6 mo - 1 year) or "older adult" (≥ 3 year), and then collected audio-recordings over a 20-day learning period to assess vocal learning ability. Following behavioral recording, immunohistochemistry was performed on collected neural tissue to measure FoxP2 protein expression in a parrot vocal learning center, the magnocellular nucleus of the medial striatum (MMSt), and its adjacent striatum., Results: Although older adults show lower vocal diversity (i.e. repertoire size) and higher absolute levels of FoxP2 in the MMSt than young adults, we find similarly persistent downregulation of FoxP2 and equivalent vocal plasticity and vocal convergence in the two age cohorts. No relationship between individual variation in vocal learning measures and FoxP2 expression was detected., Conclusions: We find neural evidence to support persistent vocal learning in the budgerigar, suggesting resilience to aging in the open-ended learning program of this species. The lack of a significant relationship between FoxP2 expression and individual variability in vocal learning performance suggests that other neurogenetic mechanisms could also regulate this complex behavior., (© 2024. The Author(s).)

Predation risk may affect the foraging behavior of birds. However, there has been little research on the ability of domestic birds to perceive predation risk and thus adjust their feeding behavior. In this study, we tested whether domestic budgerigars (Melopsittacus undulatus) perceived predation risk after the presentation of specimens and sounds of sparrowhawks (Accipiter nisus), domestic cats (Felis catus), and humans, and whether this in turn influenced their feeding behavior. When exposed to visual or acoustic stimuli, budgerigars showed significantly longer latency to feed under sparrowhawk, domestic cat, and human treatments than with controls. Budgerigars responded more strongly to acoustic stimuli than visual stimuli, and they showed the longest latency to feed and the least number of feeding times in response to sparrowhawk calls. Moreover, budgerigars showed shorter latency to feed and greater numbers of feeding times in response to human voices than to sparrowhawk or domestic cat calls. Our results suggest that domestic budgerigars may identify predation risk through visual or acoustic signals and adjust their feeding behavior accordingly., (© 2024. The Author(s).)

Digestive and respiratory tracts are inhabited by rich bacterial communities that can vary between their different segments. In comparison with other bird taxa with developed caeca, parrots that lack caeca have relatively lower variability in intestinal morphology. Here, based on 16S rRNA metabarcoding, we describe variation in microbiota across different parts of parrot digestive and respiratory tracts both at interspecies and intraspecies levels. In domesticated budgerigar (Melopsittacus undulatus), we describe the bacterial variation across eight selected sections of respiratory and digestive tracts, and three non-destructively collected sample types (faeces, and cloacal and oral swabs). Our results show important microbiota divergence between the upper and lower digestive tract, but similarities between respiratory tract and crop, and also between different intestinal segments. Faecal samples appear to provide a better proxy for intestinal microbiota composition than the cloacal swabs. Oral swabs had a similar bacterial composition as the crop and trachea. For a subset of tissues, we confirmed the same pattern also in six different parrot species. Finally, using the faeces and oral swabs in budgerigars, we revealed high oral, but low faecal microbiota stability during a 3-week period mimicking pre-experiment acclimation. Our findings provide a basis essential for microbiota-related experimental planning and result generalisation in non-poultry birds., (© 2023. The Author(s).)

Various companion birds, including budgerigars, are anesthetized with injectable anesthesia. The current study aimed to evaluate oxidative stress indices including malondialdehyde (MDA), total antioxidant capacity (TAC), total oxidant status (TOS), and oxidative stress index (OSI) along with clinical parameters such as the time required to induce, maintain and recover from medetomidine-ketamine anesthesia and midazolam-ketamine anesthesia in budgerigars. Among 20 mature and healthy budgerigars, three groups were assigned as follows: Control (n = 4) to determine baseline oxidative stress indices medetomidine + ketamine (n = 8) anesthetized by intramuscular injections of medetomidine (0.04 mg kg -1 ) and ketamine (30.00 mg kg -1 ) in the pectoral muscles, midazolam + ketamine (n = 8) anesthetized by intramuscular injections of midazolam (1.00 mg kg -1 ) and ketamine (50.00 mg kg -1 ). Half of birds (n = 4) in the second and third groups were euthanized by cervical dislocation 1 hr after anesthesia induction, blood samples were collected directly from the heart, and sera were extracted. Additionally, the remaining birds were euthanized 24 hr later, and their serum was analyzed for oxidative stress indices. Clinical parameters were recorded during the study. Compared to the medetomidine + ketamine group, the midazolam + ketamine group experienced shorter induction, anesthetic, and recovery times. Administering medetomidine and ketamine elevated TOS levels compared with midazolam + ketamine. No significant difference was found between the test groups for TAC, MDA, or OSI. Therefore, the midazolam + ketamine regimen appears superior to medetomidine + ketamine when performing minor surgeries on budgerigars., Competing Interests: The authors declare no conflict of interest., (© 2024 Urmia University. All rights reserved.)

Cochlear synaptopathy is a common pathology in humans associated with aging and potentially sound overexposure. Synaptopathy is widely expected to cause "hidden hearing loss," including difficulty perceiving speech in noise, but support for this hypothesis is controversial. Here in budgerigars (Melopsittacus undulatus), we evaluated the impact of long-term cochlear synaptopathy on behavioral discrimination of Gaussian noise (GN) and low-noise noise (LNN) signals processed to have a flatter envelope. Stimuli had center frequencies of 1-3kHz, 100-Hz bandwidth, and were presented at sensation levels (SLs) from 10 to 30dB. We reasoned that narrowband, low-SL stimuli of this type should minimize spread of excitation across auditory-nerve fibers, and hence might reveal synaptopathy-related defects if they exist. Cochlear synaptopathy was induced without hair-cell injury using kainic acid (KA). Behavioral threshold tracking experiments characterized the minimum stimulus duration above which animals could reliably discriminate between LNN and GN. Budgerigar thresholds for LNN-GN discrimination ranged from 40 to 60ms at 30dB SL, were similar across frequencies, and increased for lower SLs. Notably, animals with long-term 39-77% estimated synaptopathy performed similarly to controls, requiring on average a ∼7.5% shorter stimulus duration (-0.7±1.0dB; mean difference ±SE) for LNN-GN discrimination. Decision-variable correlation analyses of detailed behavioral response patterns showed that individual animals relied on envelope cues to discriminate LNN and GN, with lesser roles of FM and energy cues; no difference was found between KA-exposed and control groups. These results suggest that long-term cochlear synaptopathy does not impair discrimination of low-level signals with different envelope statistics., Competing Interests: Declaration of Competing Interest The authors declare no competing interests., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Parrots have enormous vocal imitation capacities and produce individually unique vocal signatures. Like songbirds, parrots have a nucleated neural song system with distinct anterior (AFP) and posterior forebrain pathways (PFP). To test if song systems of parrots and songbirds, which diverged over 50 million years ago, have a similar functional organization, we first established a neuroscience-compatible call-and-response behavioral paradigm to elicit learned contact calls in budgerigars (Melopsittacus undulatus). Using variational autoencoder-based machine learning methods, we show that contact calls within affiliated groups converge but that individuals maintain unique acoustic features, or vocal signatures, even after call convergence. Next, we transiently inactivated the outputs of AFP to test if learned vocalizations can be produced by the PFP alone. As in songbirds, AFP inactivation had an immediate effect on vocalizations, consistent with a premotor role. But in contrast to songbirds, where the isolated PFP is sufficient to produce stereotyped and acoustically normal vocalizations, isolation of the budgerigar PFP caused a degradation of call acoustic structure, stereotypy, and individual uniqueness. Thus, the contribution of AFP and the capacity of isolated PFP to produce learned vocalizations have diverged substantially between songbirds and parrots, likely driven by their distinct behavioral ecology and neural connectivity., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2023 Elsevier Inc. All rights reserved.)

A 2-year-old male budgerigar ( Melopsittacus undulatus ) died after a 1-day history of fracture of the rostral rhinotheca with pale mucous membranes, dyspnea, dull mentation, and ataxia. Histopathology revealed an infiltrative neoplasm composed of interweaving streams of spindle cells effacing the dermis and bone of the rostral upper beak as well as a ganglion and two cranial nerves. No visceral metastasis was observed. Neoplastic cells exhibited strong cytoplasmic immunolabeling for alpha-smooth muscle actin (α-SMA) and lacked immunolabeling for S100, Melan-A, PNL2, and cytokeratin AE1/AE3. These findings were consistent with a locally invasive leiomyosarcoma Leiomyosarcomas arise from the smooth muscle and are locally invasive with rare metastases. In birds, leiomyosarcomas are mostly reported to arise from the spleen, gastrointestinal, and reproductive tracts. In the case report herein, we describe the histological and immunohistochemical features of a primary beak leiomyosarcoma in a budgerigar associated with a fracture located at the rostral rhinotheca. Leiomyosarcoma arising from the beak has not been described in the literature., Competing Interests: TN was employed by Antech Diagnostics. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Rasche, Barrantes Murillo and Negrão Watanabe.)

Here, we report a parvovirus genome identified in Melopsittacus undulatus . The genome is 4,547 bp long and codes for two major open reading frames (ORFs): the non-structural replicase protein 1 (NS1) and the structural capsid gene (VP1). Phylogenetic analysis shows that this virus belongs to the genus Chaphamaparvovirus ., Competing Interests: The authors declare no conflict of interest.

Purpose: Loss of auditory nerve afferent synapses with cochlear hair cells, called cochlear synaptopathy, is a common pathology in humans caused by aging and noise overexposure. The perceptual consequences of synaptopathy in isolation from other cochlear pathologies are still unclear. Animal models provide an effective approach to resolve uncertainty regarding the physiological and perceptual consequences of auditory nerve loss, because neural lesions can be induced and readily quantified. The budgerigar, a parakeet species, has recently emerged as an animal model for synaptopathy studies based on its capacity for vocal learning and ability to behaviorally discriminate simple and complex sounds with acuity similar to humans. Kainic acid infusions in the budgerigar produce a profound reduction of compound auditory nerve responses, including wave I of the auditory brainstem response, without impacting physiological hair cell measures. These results suggest selective auditory nerve damage. However, histological correlates of neural injury from kainic acid are still lacking., Methods: We quantified the histological effects caused by intracochlear infusion of kainic acid (1 mM; 2.5 µL), and evaluated correlations between the histological and physiological assessments of auditory nerve status., Results: Kainic acid infusion in budgerigars produced pronounced loss of neural auditory nerve soma (60% on average) in the cochlear ganglion, and of peripheral axons, at time points 2 or more months following injury. The hair cell epithelium was unaffected by kainic acid. Neural loss was significantly correlated with reduction of compound auditory nerve responses and auditory brainstem response wave I., Conclusion: Compound auditory nerve responses and wave I provide a useful index of cochlear synaptopathy in this animal model., (© 2023. The Author(s) under exclusive licence to Association for Research in Otolaryngology.)

Schroeder-phase harmonic tone complexes can have a flat temporal envelope and rising or falling instantaneous-frequency sweeps within F0 periods, depending on the phase-scaling parameter C. Human tone-detection thresholds in a concurrent Schroeder masker are 10-15 dB lower for positive C values (rising frequency sweeps) compared to negative (falling sweeps), potentially due to cochlear mechanics, though this hypothesis remains controversial. Birds provide an interesting model for studies of Schroeder masking because many species produce vocalizations containing frequency sweeps. Prior behavioral studies in birds suggest less behavioral threshold difference between maskers with opposite C values than in humans, but focused on low masker F0s and did not explore neural mechanisms. We performed behavioral Schroeder-masking experiments in budgerigars (Melopsittacus undulatus) using a wide range of masker F0 and C values. Signal frequency was 2800 Hz. Neural recordings from the midbrain characterized encoding of behavioral stimuli in awake animals. Behavioral thresholds increased with increasing masker F0 and showed minimal difference between opposite C values, consistent with prior budgerigar studies. Midbrain recordings showed prominent temporal and rate-based encoding of Schroeder F0, and in many cases, marked asymmetry in Schroeder responses between C polarities. Neural thresholds for Schroeder-masked tone detection were often based on a response decrement compared to the masker alone, consistent with prominent modulation tuning in midbrain neurons, and were generally similar between opposite C values. The results highlight the likely importance of envelope cues in Schroeder masking and show that differences in supra-threshold Schroeder responses do not necessarily result in neural threshold differences., Competing Interests: Declaration of Competing Interest The authors declare no competing interests., (Copyright © 2023. Published by Elsevier B.V.)

Many birds move fast into dark nest cavities forcing the visual system to adapt to low light intensities. Their visual system takes between 15 and 60 min for complete dark adaptation, but little is known about the visual performance of birds during the first seconds in low light intensities. In a forced two-choice behavioural experiment we studied how well budgerigars can discriminate stimuli of different luminance directly after entering a darker environment. The birds made their choices within about 1 s and did not wait to adapt their visual system to the low light intensities. When moving from a bright facility into an environment with 0.5 log unit lower illuminance, the budgerigars detected targets with a luminance of 0.825 cd m -2 on a black background. When moving into an environment with 1.7 or 3.5 log units lower illuminance, they detected targets with luminances between 0.106 and 0.136 cd m -2 . In tests with two simultaneously displayed targets, the birds discriminated similar luminance differences between the targets (Weber fraction of 0.41-0.54) in all light levels. Our results support the notion that partial adaptation of bird eyes to the lower illumination occurring within 1 s allows them to safely detect and feed their chicks.

Auditory patterns carry information in human speech at multiple levels, including the surface relationships between sounds within words in phonology and the abstract structures of syntax. The sequences of other animal vocalizations, such as birdsong, can also be described as auditory patterns, but few studies have probed how the sequences are perceived at multiple levels. Past work shows that a small parrot species, the budgerigar (Melopsittacus undulatus), exceeds other birds in sequence perception and is even sensitive to abstract structure. But it is not known what level of auditory analysis is dominant in perception or what limits might exist in sensitivity to abstract structure. Here, budgerigars were tested on their ability to discriminate changes in an auditory pattern, AAB, i.e. sound-same different, to ask how they attended to surface relationships among the sounds and the abstract relationships of same/different among the elements. The results show that the budgerigars primarily used surface transitions between the sounds when discriminating the sequences, but were able to use the abstract relationships to a limited extent, largely restricted to two elements. This study provides insight into how budgerigars extract information from conspecific vocalizations and how their capacities compare to human speech perception., (Copyright © 2022 Elsevier B.V. All rights reserved.)

This study examined the effects of exposure to coloured LED lights on some behavioural responses, food and water consumption, and live weight in budgerigars kept in captivity using behavioural tests to compare different lighting conditions. Budgerigars' feeding, comfort, social, fear, and resting behaviours and behavioural reactions to a new environment were studied. Twelve male birds were assigned to four groups, with three birds in each group. They were provided with food and water ad libitum in wire cages at 25 ± 2 °C in a room. The study was conducted with 10 h of natural light, 6 h of LED light (white, blue, yellow, and red LED lights), and 8 h of darkness. Their behaviours in the cages were observed. Home cage avoidance (HCA) and two open field tests (OFT) were performed. No difference was observed in the LW and food consumption, but the blue and yellow groups consumed less water. The blue group displayed more comfort and social behaviours. In the HCA test, the red group demonstrated higher reactions. Furthermore, the birds in the yellow group stayed closer to the centre of the platform in the OFT I test, and they chose the compartment simulating their familiar environment in the OFT II test. Consequently, it was concluded that first yellow and then blue lights may be used to prevent stress-related problems for these birds. Our findings could be used to improve the hand-rearing conditions of captive budgerigars.

Currently, drug-induced stimulation of appetite is not commonly performed in hyporexic or anorexic companion psittacine birds. Instead, to prevent a catabolic state and weight loss, supplemental feedings are routinely performed by crop gavage. However, crop gavage is not without complications and is stressful to the patient and labor intensive. The objective of this study was to evaluate the effect of midazolam on food intake in healthy budgerigars. In a randomized, blinded, controlled study, change in food intake after intramuscular administration of midazolam (1 mg/kg) or a placebo-control treatment (0.9% saline) was evaluated in 12 healthy adult budgerigars ( Melopsittacus undulatus ). Food intake was quantified for 1 hour before and after drug administration. Birds were monitored for feeding behavior as well as signs of sedation. After midazolam administration, a median 6-fold (1.1-28) increase in food intake was recorded. In 3 of 6 (50%) birds, the food intake increase after midazolam administration was >10-fold (median 17-fold [10-28]), whereas in the remaining 3 birds, food intake increased by only 1.7-fold (1.1-1.8). The median amount of food ingested (16.7 g/kg [3.2-43.2 g/kg]) was significantly higher after midazolam administration compared with the control group (1.9 g/kg [0.0-19.7 g/kg], P = .015). The median time birds spent displaying feeding behavior after the midazolam injection was 18% (0-43%), compared with 1% (0-20%) in the control group after saline injection. Five of 6 (83%) birds showed signs consistent with mild sedation after midazolam administration. This study demonstrates that midazolam is an appetite stimulant in budgerigars. Future studies are needed to evaluate whether midazolam's effects on food intake are dose dependent and whether the duration of effect exceeds 1 hour.

Medullary bone is a calcium-rich, labile bone normally occurring in female birds with each egg-laying cycle. The stimulus for formation of medullary bone is, in part, the cyclic increase in serum estrogens produced by preovulatory ovarian follicles. Increased bone density due to formation of medullary bone, particularly in pneumatic bones, has been termed polyostotic hyperostosis, even if physiologic. This study investigated the formation of medullary bone in nonpneumatic (femur) and pneumatic (humerus) bones in sexually mature male budgerigars submitted for autopsy. Of the 21 sexually mature male budgerigars submitted for autopsy, 7 (33%) had medullary bone in 1 or more bones examined. All 7 male budgerigars with medullary bone had a testicular neoplasm, which was morphologically consistent with a testicular sustentacular cell tumor, seminoma, or interstitial cell tumor. Medullary bone was not present in the 14 cases with other diseases. Medullary bone formation in pneumatic and nonpneumatic bones can occur in male budgerigars with testicular neoplasms. Radiographic increases in medullary bone density, particularly in the humerus, could provide antemortem indication of testicular neoplasia in male budgerigars.

Xanthogranulomatosis is an inflammatory lesion characterized by lipid-containing macrophages, extracellular lipid, hemorrhage, and necrosis. We describe disseminated intracoelomic xanthogranulomatosis in 5 eclectus parrots ( Eclectus roratus ) and 2 budgerigars ( Melopsittacus undulatus ). Postmortem, clinicopathologic, and historical case material was reviewed. Ages ranged from 3 to 24 years; there were 5 males and 2 females. Table food was included in the diet of 3/5 cases, and animal products were included in 2/3 cases. Common clinicopathologic abnormalities included leukocytosis (4/5 cases) and elevated concentrations of bile acids (3/4 cases) and cholesterol within 6 months prior to death (2/4 cases). At postmortem examination, all 7 birds had grossly visible, irregular, soft, tan to yellow, amorphous plaques distributed on the surfaces of the viscera and body wall. Histologic evaluation and oil red O stain revealed xanthogranulomatous inflammation with phagocytized and extracellular lipid, necrosis, cholesterol clefts, fibrosis, and mineralization. Infectious agents were not identified with special stains in all cases. Concurrent hepatobiliary disease was present in 6/7 cases, and 6/7 had lipid accumulation within the parenchyma of various visceral organs. Five cases had atherosclerosis of great vessels. We describe a unique form of disseminated coelomic xanthogranulomatosis in 2 psittacine species. This condition should be recognized as a differential diagnosis in cases of disseminated coelomic mass formation and coelomic distension in psittacine birds, particularly in eclectus parrots and budgerigars.

In recent years, researchers have been attempting to relate differences in personality (e.g., boldness, aggressiveness, exploration tendency) to variation in cognition (performances in tasks that require learning, reasoning, attention, or memory, etc.) both theoretically and empirically. However, it is unclear on what basis personality and cognition might be associated with each other. Previous theory suggests a connection between fast-slow personality types and cognitive speed-accuracy tradeoffs. In this study, we tested this hypothesis in budgerigars and found that, in their 1st associative learning, birds with fast personality (less fearful of handling stress) were fast learners in the beginning, while slow personality individuals improved faster, but both types of birds did not differ in accuracy. However, these relationships were context-dependent. No significant relationship was found in subsequent learning tasks (reversal learning and a 2nd associative learning) in the familiar context (task setup and apparatus similar to the 1st associative learning). We then conducted a problem-solving experiment with novel setup and apparatus to test 1 possible explanation that the association between personality and cognition in the 1st associative learning might be caused by noncognitive constraint, such as fearfulness when facing novel task setup and apparatus. We found that fast individuals interacted more with the problem box and solved it, whereas the slow birds were not. We suggest that personalities can influence cognitive performances and trigger a cognitive speed-improvement tradeoff under the novel context. However, there are no consistent cognitive styles that co-varied with different personalities., (© The Author(s) (2021). Published by Oxford University Press on behalf of Editorial Office, Current Zoology.)

Hearing in noise is a problem often assumed to depend on encoding of energy level by channels tuned to target frequencies, but few studies have tested this hypothesis. The present study examined neural correlates of behavioral tone-in-noise (TIN) detection in budgerigars ( Melopsittacus undulatus , either sex), a parakeet species with human-like behavioral sensitivity to many simple and complex sounds. Behavioral sensitivity to tones in band-limited noise was assessed using operant-conditioning procedures. Neural recordings were made in awake animals from midbrain-level neurons in the inferior colliculus, the first processing stage of the ascending auditory pathway with pronounced rate-based encoding of stimulus amplitude modulation. Budgerigar TIN detection thresholds were similar to human thresholds across the full range of frequencies (0.5-4 kHz) and noise levels (45-85 dB SPL) tested. Also as in humans, thresholds were minimally affected by a challenging roving-level condition with random variation in background-noise level. Many midbrain neurons showed a decreasing response rate as TIN signal-to-noise ratio (SNR) was increased by elevating the tone level, a pattern attributable to amplitude-modulation tuning in these cells and the fact that higher SNR tone-plus-noise stimuli have flatter amplitude envelopes. TIN thresholds of individual neurons were as sensitive as behavioral thresholds under most conditions, perhaps surprisingly even when the unit's characteristic frequency was tuned an octave or more away from the test frequency. A model that combined responses of two cell types enhanced TIN sensitivity in the roving-level condition. These results highlight the importance of midbrain-level envelope encoding and off-frequency neural channels for hearing in noise. SIGNIFICANCE STATEMENT Detection of target sounds in noise is often assumed to depend on energy-level encoding by neural processing channels tuned to the target frequency. In contrast, we found that tone-in-noise sensitivity in budgerigars was often greatest in midbrain neurons not tuned to the test frequency, underscoring the potential importance of off-frequency channels for perception. Furthermore, the results highlight the importance of envelope processing for hearing in noise, especially under challenging conditions with random variation in background noise level over time., (Copyright © 2021 the authors.)

Budgerigars (Melopsittacus undulatus) are small Australian parrots with a well-documented, learned vocal repertoire and a high degree of vocal production learning. These birds live in large, social flocks and they vocally interact with each other in a dynamic, reciprocal manner. We assume that budgerigars must process and integrate a wide variety of sensory stimuli when selecting appropriate vocal responses to conspecifics during vocal interactions, but the relative contributions of these different stimuli to that process are next to impossible to tease apart in a natural context. Here we show that budgerigars, under operant control, can learn to respond to specific stimuli with a specific vocal response. Budgerigars were trained to produce contact calls to a combination of auditory and visual cues. Birds learned to produce specific contact calls to stimuli that differed either in location (visual or auditory) or quality (visual). Interestingly, the birds could not learn to associate different vocal responses with different auditory stimuli coming from the same location. Surprisingly, this was so even when the auditory stimuli and the responses were the same (i.e., the bird's own contact call). These results show that even in a highly controlled operant context, acoustic cues alone were not sufficient to support vocal production learning in budgerigars. From a different perspective, these results highlight the significant role that social interaction likely plays in vocal production learning so elegantly shown by Irene Pepperberg's work in parrots.

A 52-year-old woman presented to a clinic in late August with exacerbated fatigue and dyspnea on exertion for several months. Then, she was referred and admitted to our hospital in late September. Her chest CT showed bilateral diffuse centrilobular micronodules. In her detailed clinical history, she had kept budgerigars indoors for 15 years. These findings suggested she had a bird-related hypersensitivity pneumonitis (BRHP). By a site environmental investigation, 40 budgerigars were kept in a single breeding room and there were large amounts of droppings on the floor. Serum specific antibody for bird antigens and an environmental provocation test were positive. Bronchoalveolar lavage fluid showed lymphocytosis and a low CD4/CD8 ratio. Trans-bronchial lung biopsy showed lymphocytic infiltration of the alveolar wall and interlobular septa. After antigen avoidance as hospitalization, her symptoms and abnormal shadow improved. From these results, the patient was diagnosed as an acute BRHP.BRHP often presents a chronic onset. This case was diagnosed as an acute type despite the 15-years of budgerigars breeding. Increased exposure of antigens due to lack of cleaning after several days' antigen avoidance was suspected with one of the causes of acute onset.

Over a 4-mo period, a Michigan zoo had 32 budgerigars, Melopsittacus undulatus, from their flock die. Whole animals or formalin-fixed tissues were submitted to Michigan State University Veterinary Diagnostic Laboratory for diagnosis. Avian gastric yeast infection, Macrorhabdus ornithogaster, was diagnosed in seven birds. There was atrophy of breast musculature and no subcutaneous or coelomic fat stores in six necropsied birds. Only two birds had proventricular dilatation grossly. Histologic examination of the proventriculus of all seven birds revealed abundant 3 × 50-µm septate, parallel-walled, nonbranching yeast organisms morphologically consistent with Macrorhabdus ornithogaster. Mycobacteriosis was diagnosed in three budgerigars, two of which were necropsied. Both necropsied birds had hepatomegaly and one also had splenomegaly. No acid-fast bacilli were found in the livers of either bird but were found in splenic macrophages of the bird with splenomegaly and in the intestine of the other bird. Mycobacterium species were cultured from the enlarged spleen and identified by DNA sequence as Mycobacterium genavense. Pulmonary granulomas with acid-fast bacilli were found in the bird submitted as fixed tissues. None of the budgerigars had a dual infection. The remainder of the budgerigars died from hepatitis, nephrosis, oviductal prolapse, exclusion from food and water by flock mates, or tumors.

Encephalitozoon spp. and Enterocytozoon bieneusi are well-known microsporidian pathogens, recently classified as fungi, infecting humans and reptiles, mammals, and birds. Budgerigars (Melopsittacus undulates) are the most preferred captive pet birds in the households. Prevalence and molecular data on microsporidian species in budgerigars are scarce worldwide. The aim of the present study was to investigate the occurrence and genotypes of Encephalitozoon spp. and E. bieneusi in budgerigars, and to reveal their zoonotic potential. A total of 143 fecal samples were collected from owned healthy budgerigars in Turkey. Encephalitozoon spp. and E. bieneusi were examined by nested PCR targeting the ribosomal internal transcribed spacer (ITS) region and sequenced for identifying Encephalitozoon spp. and E. bieneusi. The overall prevalence of E. hellem and E. bieneusi was 14.7% (21/143) and 3.5% (5/143), respectively. Two genotypes of E. hellem were identified, including one known 1A (n = 18) and a novel TURK1B (n = 3). In addition, we determined two E. bieneusi genotypes, including one known N (n = 2) and a novel TURKM1 (n = 3). E. hellem 1A and novel TURK1B clustered as a sister taxon, and genotype N and novel TURKM1 genotypes fall into group 2 of E. bieneusi in the phylogenetic tree. Novel genotypes of E. hellem and E. bieneusi were described for the first time in the avian host. Moreover, E. bieneusi genotype N was first detected in avian hosts in the present study. This study contributes to the current knowledge on the molecular epidemiology and transmission dynamics of E. hellem and E. bieneusi., Lay Summary: Spore producing microsporidia are ubiquitous, obligate, and intracellular fungus defined as emerging opportunistic pathogens of humans, livestock, companion animals, wild mammals, birds, and water worldwide. The occurrence of microsporidia in animals could be risky for human public health., (© The Author(s) 2020. Published by Oxford University Press on behalf of The International Society for Human and Animal Mycology.)

A grey-hooded parakeet ( Psilopsiagon aymara ) and two budgerigars ( Melopsittacus undulatus ) from different owners presented with decreased activity, vomitus, and diarrhea. A microscopic examination of feces showed trophozoites of the protozoan flagellate Giardia . A commercial immunochromatographic dipstick test for Giardia sp. antigens confirmed the infection. These findings were assured by PCR of the small subunit ribosomal RNA (SSU rRNA) gene and coproantigen ELISA. Sequencing of PCR products of the SSU rRNA (292 bp) and β-giardin genes (511 bp) identified Giardia psittaci as the species involved. Therefore, our results show that a GSA 65-based coproantigen ELISA, which was established for diagnosis of Giardia duodenalis is applicable for the detection of G. psittaci . A treatment with ronidazole was started. Additionally, fecal examination and dissection of the dead birds revealed coinfection with the fungal pathogen Macrorhabdus ornithogaster . One budgerigar survived and repeatedly tested negative after treatment with ronidazole. The described cases indicate that a single infection with G. psittaci has a good prognosis, whereas the prognosis is poor when coinfections occur, especially with M. ornithogaster .

Alfaxalone is a neurosteroid anesthetic agent that has been extensively used in both human and veterinary medicine for more than 50 yr. Previous studies involving avian species demonstrated various dose ranges and multiple routes of administration. The aim of this study was to evaluate the short-term sedative, cardiorespiratory, and thermoregulatory effects of an intramuscular injection of alfaxalone on budgerigars ( Melopsittacus undulatus ). A crossover study was performed with a sample size of 10 male budgerigars, previously determined to be healthy based on physical examination. Alfaxalone was administered intramuscularly at two doses: 15 and 20 mg/kg. The lower dose resulted in mild to moderate sedation for 29 ± 5 min, whereas the higher dose resulted in moderate to profound sedation for 29 ± 7 min. A statistically significant decrease in heart rate was observed 2 min after administration of alfaxalone at 15 mg/kg; however, this finding was noted to be transient. A statistically significant decrease in respiratory rate was observed at 6 and 10 min after injection in both groups. Cloacal temperature measurement with a digital thermometer and eye temperature calculated from thermographic images demonstrated a decrease in body temperature over time but was not found to be statistically significant. Intramuscular use of alfaxalone proved to provide short-term sedation in budgerigars, with statistically significant but clinically mild cardiorespiratory effects. Due to a significant decrease in body temperature, active warming is recommended when using alfaxalone in budgerigars.

Proper diet and nutrition are essential for maintaining the health of captive birds, but specific nutritional requirements can vary by species. Our knowledge of avian nutrition is predominantly based on data collected from gallinaceous birds, which is the primary basis for the dietary recommendations for companion birds, such as budgerigars ( Melopsittacus undulatus ) and other psittacine birds, potentially leading to a higher risk of malnutrition. In the wild, budgerigars eat predominantly Australian grass seed of the Astrebla genus, which may not be similar to the commercially available food fed to captive budgerigars, both in nutrient content and in their physiologic effects. In this study, we examined the relationship between diet type and immune function by separating 36 budgerigars into 3 dietary treatments: 1) Roudybush formulated pellet diet (Roudybush BirdFood Inc, Woodland, CA, USA), 2) Kaytee Forti-Diet Pro Health seed mix (Kaytee Products Inc, Chilton, WI, USA), and 3) a natural seed diet containing fresh canary grass, flax, nyger, oat groats, and white millet seeds. We monitored body weight, measured the microbial killing ability of whole blood by Escherichia coli and Candida albicans , and collected blood smears to assess white blood cell counts during a period of 8 weeks. Overall, we observed no significant effects of the 3 different diets on bird microbial killing ability or on white blood cell counts, suggesting similar health outcomes for budgerigars that consume mixed seed and those that receive pellet-based diets during this relatively short-term study.

Aves polyomavirus 1 (APV) causes inflammatory disease in psittacine birds, especially in young budgerigar. In this study, an APV virus (SD18 strain) was isolated from a diseased psittacine birds breeding facility. The full genome (4981 bp) of SD18 was determined and analyzed. Phylogenetic analysis of full genome sequences indicated all the APV strains form two groups. The SD18 strain showed close relationship with APV isolated from Poland, however, the other Chinese strains are located in group II, which suggested different genotypes APVs are co-circulating in China. Compared with the consensus sequence of APV full genome, the SD18 strain contains 13 nucleotide mutations, and 2 unique amino acid substitutions (R179M and Q382K) located in VP2/3 and Large T proteins. To explore the pathogenicity of the virus, the SD18 strain was used to challenge 2-week-old budgerigars. All infected birds died no later than 5 days post infection, and virus was detected in multiple organs including brain, heart, ingluvies, liver, and intestine, which indicated that SD18 is fatal and causes systemic infection in young budgerigar. In vitro studies showed that SD18 replicated efficiently in CEF cells and reached the highest viral titers at 9 days post infection. Notably, replication of SD18 stimulated IFN-β response in CEF cells and overexpression of the VP4 or VP4Delta proteins significantly inhibited IFN-β promoter activation, which could be the strategy of APV to escape from the host innate immunity., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Macrorhabdosis is a debilitating disease condition that affects budgerigars ( Melopsittacus undulatus ), cockatiels ( Nymphicus hollandicus ), and many other bird species worldwide. Macrorhabdus ornithogaster is a pathogen which leads to nonspecific clinical signs, and to date, diagnosis as well as therapy are still challenging. In this study, medical histories of 32 budgerigars and 7 cockatiels with macrorhabdosis diagnosed clinically and by polymerase chain reaction (PCR) within a period of 24 months (from January 2016 to January 2018) were retrospectively analyzed. Macrorhabdus ornithogaster was diagnosed through fecal samples collected over several days and analyzed by microscopic examination or PCR. The effectiveness of 2 different amphotericin B treatment regimens were investigated by PCR. In 23 cases, treatment was performed with amphotericin B via drinking water at 0.1 mg/mL for 28 days. For the remaining 16 birds, an alternative treatment regimen of amphotericin B at 100 mg/kg PO q12h for 10 days was combined with administration of amphotericin B via drinking water at 0.1 mg/mL for 28 days. Fecal samples of all treated flocks were reexamined by PCR 10-14 days post-amphotericin B treatment. More than half (56.4%) of the treated birds tested negative for M ornithogaster irrespective of the treatment regimen. In addition to clinical improvement and microscopic examination of droppings, PCR was used for the first time to evaluate treatment response in birds diagnosed with M ornithogaster . Administration of amphotericin B via drinking water proved to be effective in more than 50% of cases, indicating a less stressful alternative to the oral administration of amphotericin B twice daily.

Budgerigar is a common name for a colorful Australian native bird belonging to the Melopsittacus undulatus species. It is a very familiar pet around the world and its breeding has been grown in Iran. This study was conducted on a 2-year-old budgerigar with a nodular mass on the left wing. Physical examination revealed a firm, round and well-circumscribed mass approximately 1.70 cm in diameter. Radiographs showed a soft tissue mass with no involvement of bony structures. Fine needle aspiration was performed and the sample was cultured. In cultural examination, Klebsiella spp. were isolated in pure culture. Genus and species of the bacteria were confirmed using multiplex polymerase chain reaction. The mass was surgically excised and it was mainly composed of numerous, large lipid-laden macrophages containing abundant vacuolated cytoplasm, extracellular acicular cholesterol clefts and large number of multinucleated giant cells (especially multinucleated Touton giant cells) in the dermis. Finally, a diagnosis of cutaneous xanthogranuloma was made based on histopathological findings., (© 2019 Urmia University. All rights reserved.)

Psittacine beak and feather disease (PBFD) is a common disease in psittacine bird that caused by beak and feather disease virus (BFDV). BFDV is widely spread and threatening psittacine birds worldwide. However, the BFDV infection in China remains largely unknown. In this study, a surveillance study of BFDV was conducted in three budgerigar breeding facilities, which showed that 66.6% of collected faeces samples were positive for BFDV. Full genomes of nine BFDV circulating in the three budgerigar breeding facilities (three for each facility) were determined and analysed. The full genomes shared 75.9% to 87.5% identity with the known genotype BFDV. Phylogenetic analysis of the full genome indicated that the BFDV circulating in China formed a separated group, and the nine isolates fell into three subgroups, suggesting that different unique BFDV genotypes are circulating in China. Notably, the Cap genes of three strains (SD3, SD5 and SD9) showed low identity (67.9% to 70%) to all the known genotypes of BFDV. Phylogenetic analysis showed that these three Cap genes formed a unique lineage that is different from all known genotypes, which suggested that the SD3, SD5 and SD9 strains identified in this study belong to a novel genotype that has not been reported. However, the origin of this genotype remains unclear. All the data indicated that the different unique genotypes of BFDV are co-circulating in China, and active surveillance of BFDV is warranted., (© 2019 Blackwell Verlag GmbH.)

In many bird species, male song functions both to defend a territory against other males and to attract a female mate. Male budgerigars (Melopsittacus undulatus) produce a song-like vocal signal, the warble, that can be directed at either females or other males. Warble is a long, complex, low amplitude, and variable vocalization composed of different element types. While there is some evidence that warble can induce reproduction, the function of this signal is largely uncertain and it is unclear whether male- and female-directed warble differ in either function or structure. We recorded male budgerigars in the presence of either their mate or a familiar male to identify whether the warbles produced with different audiences differed in structure. We dissected each warble into specific element units, classified units into a limited number of types by rule-based visual classification and calculated the proportion of each element type, element diversity, and total duration for the male- and female-directed warbles of each male. We also examined the sequential organization of warble element types (syntax) using time-window lagged sequential analysis. We found no differences in the proportions of different elements used, element diversity or duration of warbles between male- and female-directed warble. The syntax of warbles is similar when directed at males or females. However, we found greater between-individual similarity in the sequential organization of warbles directed towards females than in those directed towards males. The greater syntactical consistency in female-directed warble suggests that females may prefer either specific types of element sequences, or consistency itself, and thus shape the organization of warbles., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Auditory-nerve fibers are lost steadily with age and as a possible consequence of noise-induced glutamate excitotoxicity. Auditory-nerve loss in the absence of other cochlear pathologies is thought to be undetectable with a pure-tone audiogram while degrading real-world speech perception (hidden hearing loss). Perceptual deficits remain unclear, however, due in part to the limited behavioral capacity of existing rodent models to discriminate complex sounds. The budgerigar is an avian vocal learner with human-like behavioral sensitivity to many simple and complex sounds and the capacity to mimic speech. Previous studies in this species show that intracochlear kainic-acid infusion reduces wave 1 of the auditory brainstem response by 40-70%, consistent with substantial excitotoxic auditory-nerve damage. The present study used operant-conditioning procedures in trained budgerigars to quantify kainic-acid effects on tone detection across frequency (0.25-8 kHz; the audiogram) and as a function of duration (20-160 ms; temporal integration). Tone thresholds in control animals were lowest from 1 to 4 kHz and decreased with increasing duration as in previous studies of the budgerigar. Behavioral results in kainic-acid-exposed animals were as sensitive as in controls, suggesting preservation of the audiogram and temporal integration despite auditory-nerve loss associated with up to 70% wave 1 reduction. Distortion-product otoacoustic emissions were also preserved in kainic-acid exposed animals, consistent with normal hair-cell function. These results highlight considerable perceptual resistance of tone-detection performance with selective auditory-nerve loss. Future behavioral studies in budgerigars with auditory-nerve damage can use complex speech-like stimuli to help clarify aspects of auditory perception impacted by this common cochlear pathology., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Bacteria isolated from lesions as well as apparently normal tissues of psittacine birds have previously been reported as taxon 37 and taxon 44 of Bisgaard. 16S rRNA gene sequence comparisons revealed a distant relationship to members of Pasteurellaceae at the species, genus and family levels. The polar lipid profile consisted of the major components phosphatidylethanolamine and phosphatidylglycerol. A new family Psittacicellaceae fam. nov. is proposed with the type genus Psittacicella gen. nov. The new genus Psittacicella includes the type species Psittacicella melopsittaci sp. nov. with type strain B96/4 T (=CCUG 70858 T =DSM 105476 T ), Psittacicella hinzii sp. nov. with type strain 111 T (=CCUG 52861 T =CCM 8842 T ) and Psittacicella gerlachiana sp. nov. with type strain EEAB3T1 T (=CCUG 70857 T =DSM 105477 T ). In addition to the major polar lipids, strain 111 T possessed the non-identified aminophospholipids APL1 and APL2 and trace amounts of four lipids (L1-L4) whereas strain B94/4 T showed the minor unidentified aminophospholipids APL3 and APL2 and trace amounts of unidentified lipid L3. These results demonstrate that strain B96/4 T can be distinguished from 111 T based on presence/absence of the unidentified lipids APL1 and APL3. The total polar lipid profile of strain EEAB3T1 T differed from B96/4 T only in one minor lipid. Strain B96/4 T can further be distinguished from 111 T by acid formation from trehalose and raffinose and the α-glucosidase test. Strains 111 T and EEAB3T1 T can be separated based on acid formation from trehalose and the α-glucosidase test. Strains B96/4 T and EEAB3T1 T can be separated by acid formation from raffinose and eight signature indels in the RpoB protein.

Intramuscular (IM) administration of either alfaxalone or butorphanol with midazolam was evaluated for sedation and effects on heart and respiratory rates in budgerigars ( Melopsittacus undulatus ). Twenty adult budgerigars were randomly assigned to receive 1 of 2 treatments: alfaxalone at 15 mg/kg IM or butorphanol and midazolam at 2.5 mg/kg IM and 1.25 mg/kg IM, respectively. Baseline heart and respiratory rates and sedation score were collected and, after injection, time to initial effects and initial recumbency were recorded. Five minutes after injection, birds were assessed for a righting reflex, and, if absent, response to noxious stimulus was assessed by hemostat clamp on the first digit. Birds then underwent a standardized diagnostic evaluation of radiographs, jugular venipuncture, and physical examination. At the end of the physical examination, a sedation score was assigned, and birds were placed in dorsal recumbency for recovery. Times from injection to initial arousal, final recumbency, standing, and full recovery were recorded. Although time to onset of sedation was the same between groups, alfaxalone produced a shorter ( P = .04) and more consistent duration of sedation (mean ± SD: 27.5 ± 5.9 minutes) compared with butorphanol-midazolam (72.0 ± 56.9 minutes). Only 3 of 10 birds receiving butorphanol-midazolam were recumbent by 5 minutes compared with 10 of 10 birds receiving alfaxalone. Radiographs were successfully obtained in 9 of 10 and 7 of 10 birds administered alfaxalone and butorphanol-midazolam, respectively. No adverse effects were observed in any bird. Intramuscular alfaxalone produces safe, effective, and reliable sedation in budgerigars and is a more consistent and shorter duration alternative to intramuscular butorphanol-midazolam., (© 2018 by the Association of Avian Veterinarians.)

To study the fitness effects of individual variation in cognitive traits, it is paramount to understand whether traits such as personality and physiological stress influence cognitive performance. We first tested whether budgerigars showed both consistent personalities and cognitive performance across time and tasks. We tested object and food neophobia, and exploratory behavior. We measured cognitive performance in habituation, ability to solve foraging problems, spatial memory, and seed discrimination tasks. Budgerigars showed consistency in their neophobic tendencies and these tendencies were associated with their exploratory behavior. Birds were also consistent in how they performed in most of the cognitive tasks (temporal consistency), but were not consistent in their performance across tasks (context consistency). Neither corticosterone levels (baseline and stress-induced) showed a significant relationship with either cognitive or personality measures. Neophobic and exploratory tendencies determined the willingness of birds to engage only in the seed discrimination task. Such tendencies also had a significant effect on problem-solving ability. Our results suggest that consistent individual differences in cognitive performance along with consistent differences in personality could determine response to environmental change and therefore have important fitness consequences.

Parrot feathers contain red, orange, and yellow polyene pigments called psittacofulvins. Budgerigars are parrots that have been extensively bred for plumage traits during the last century, but the underlying genes are unknown. Here we use genome-wide association mapping and gene-expression analysis to map the Mendelian blue locus, which abolishes yellow pigmentation in the budgerigar. We find that the blue trait maps to a single amino acid substitution (R644W) in an uncharacterized polyketide synthase (MuPKS). When we expressed MuPKS heterologously in yeast, yellow pigments accumulated. Mass spectrometry confirmed that these yellow pigments match those found in feathers. The R644W substitution abolished MuPKS activity. Furthermore, gene-expression data from feathers of different bird species suggest that parrots acquired their colors through regulatory changes that drive high expression of MuPKS in feather epithelia. Our data also help formulate biochemical models that may explain natural color variation in parrots. VIDEO ABSTRACT., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The current study further characterized personality types in Budgerigars, an avian model that only recently demonstrated individual consistencies in behavior (Callicrate et al., 2011). Several methodological techniques, commonly used in previous examinations of other animal models, were employed. Specifically, Phase I assessed the relationship between Budgerigar personality types and Hypothalamic-Pituitary-Adrenal (HPA) activity, while Phase II sought to examine the persistence of individual behavioral tendencies across varying testing contexts. In comparison to other species, our findings failed to illustrate a clear relationship between Budgerigar personality types and concentrations of corticosterone. However, results provided significant evidence for the consistency of personalities across multiple contexts. In sum, our investigation further defined the expression of personality in the Budgerigar and substantiated the claim for individual tendencies in this species., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Peter Marler's fascination with richness of birdsong included the notion that birds attended to some acoustic features of birdsong, likely in the time domain, which were inaccessible to human listeners. While a considerable amount is known about hearing and vocal communication in birds, how exactly birds perceive their auditory world still remains somewhat of a mystery. For sure, field and laboratory studies suggest that birds hear the spectral, gross temporal features (i.e. envelope) and perhaps syntax of birdsong much like we do. However, there is also ample anecdotal evidence that birds are consistently more sensitive than humans to at least some aspects of their song. Here we review several psychophysical studies supporting Marler's intuitions that birds have both an exquisite sensitivity to temporal fine structure and may be able to focus their auditory attention on critical acoustic details of their vocalizations. Zebra finches, Taeniopygia guttata , particularly, seem to be extremely sensitive to temporal fine structure in both synthetic stimuli and natural vocalizations. This finding, together with recent research highlighting the complexity of zebra finch vocalizations across contexts, raises interesting questions about what information zebra finches may be communicating in temporal fine structure. Together these findings show there is an acoustic richness in bird vocalizations that is available to birds but likely out of reach for human listeners. Depending on the universality of these findings, it raises questions about how we approach the study of birdsong and whether potentially significant information is routinely being encoded in the temporal fine structure of avian vocal signals.

Vowels make a strong contribution to speech perception under natural conditions. Vowels are encoded in the auditory nerve primarily through neural synchrony to temporal fine structure and to envelope fluctuations rather than through average discharge rate. Neural synchrony is thought to contribute less to vowel coding in central auditory nuclei, consistent with more limited synchronization to fine structure and the emergence of average-rate coding of envelope fluctuations. However, this hypothesis is largely unexplored, especially in background noise. The present study examined coding mechanisms at the level of the midbrain that support behavioral sensitivity to simple vowel-like sounds using neurophysiological recordings and matched behavioral experiments in the budgerigar. Stimuli were harmonic tone complexes with energy concentrated at one spectral peak, or formant frequency, presented in quiet and in noise. Behavioral thresholds for formant-frequency discrimination decreased with increasing amplitude of stimulus envelope fluctuations, increased in noise, and were similar between budgerigars and humans. Multiunit recordings in awake birds showed that the midbrain encodes vowel-like sounds both through response synchrony to envelope structure and through average rate. Whereas neural discrimination thresholds based on either coding scheme were sufficient to support behavioral thresholds in quiet, only synchrony-based neural thresholds could account for behavioral thresholds in background noise. These results reveal an incomplete transformation to average-rate coding of vowel-like sounds in the midbrain. Model simulations suggest that this transformation emerges due to modulation tuning, which is shared between birds and mammals. Furthermore, the results underscore the behavioral relevance of envelope synchrony in the midbrain for detection of small differences in vowel formant frequency under real-world listening conditions., Competing Interests: The authors declare that they have no conflict of interest.

A variety of parrot species have recently gained attention as members of a small group of non-human animals that are capable of coordinating their movements in time with a rhythmic pulse. This capacity is highly developed in humans, who display unparalleled sensitivity to musical beats and appear to prefer rhythmically organized sounds in their music. Do parrots also exhibit a preference for rhythmic over arrhythmic sounds? Here, we presented humans and budgerigars ( Melopsittacus undulatus ) - a small parrot species that have been shown to be able to align movements with a beat - with rhythmic and arrhythmic sound patterns in an acoustic place preference paradigm. Both species were allowed to explore an environment for 5 min. We quantified how much time they spent in proximity to rhythmic vs. arrhythmic stimuli. The results show that humans spent more time with rhythmic stimuli, and also preferred rhythmic stimuli when directly asked in a post-test survey. Budgerigars did not show any such overall preferences. However, further examination of the budgerigar results showed an effect of sex, such that male budgerigars spent more time with arrthymic stimuli, and female budgerigars spent more time with rhythmic stimuli. Our results support the idea that rhythmic information is interesting to budgerigars. We suggest that future investigations into the temporal characteristics of naturalistic social behaviors in budgerigars, such as courtship vocalizations and head-bobbing displays, may help explain the sex difference we observed.

Whereas it is clear from anatomical studies that all birds have complex interaural canals connecting their middle ears, the effect of interaural coupling on directional hearing has been disputed. A reason for conflicting results in earlier studies may have been that the function of the tympanic ear and hence of the interaural coupling is sensitive to variations in the intracranial air pressure. In awake birds, the middle ears and connected cavities are vented actively through the pharyngotympanic tube. This venting reflex seems to be suppressed in anesthetized birds, leading to increasingly lower pressure in the interaural cavities, stiffening the eardrums, and displacing them medially. This causes the sensitivity, as well as the interaural coupling, to drop. Conversely, when the middle ears are properly vented, robust directional eardrum responses, most likely caused by internal coupling, have been reported. The anatomical basis of this coupling is the 'interaural canal,' which turns out to be a highly complex canal and cavity system, which we describe for the zebra finch. Surprisingly, given the complexity of the interaural canals, simple models of pipe-coupled middle ears fit the eardrum directionality data quite well, but future models taking the complex anatomy into consideration should be developed.

Humans communicate with one another not only face-to-face but also via modern telecommunication methods such as television and video conferencing. We readily detect the difference between people actively communicating with us and people merely acting via a broadcasting system. We developed an animal model of this novel communication method seen in humans to determine whether animals also make this distinction. We built a system for two animals to interact via audio-visual equipment in real-time, to compare behavioral differences between two conditions, an "interactive two-way condition" and a "non-interactive (one-way) condition." We measured birds' responses to stimuli which appeared in these two conditions. We used budgerigars, which are small, gregarious birds, and found that the frequency of vocal interaction with other individuals did not differ between the two conditions. However, body synchrony between the two birds was observed more often in the interactive condition, suggesting budgerigars recognized the difference between these interactive and non-interactive conditions on some level., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Amplitude modulation (AM) is a crucial feature of many communication signals, including speech. Whereas average discharge rates in the auditory midbrain correlate with behavioral AM sensitivity in rabbits, the neural bases of AM sensitivity in species with human-like behavioral acuity are unexplored. Here, we used parallel behavioral and neurophysiological experiments to explore the neural (midbrain) bases of AM perception in an avian speech mimic, the budgerigar (Melopsittacus undulatus). Behavioral AM sensitivity was quantified using operant conditioning procedures. Neural AM sensitivity was studied using chronically implanted microelectrodes in awake, unrestrained birds. Average discharge rates of multiunit recording sites in the budgerigar midbrain were insufficient to explain behavioral sensitivity to modulation frequencies <100 Hz for both tone- and noise-carrier stimuli, even with optimal pooling of information across recording sites. Neural envelope synchrony, in contrast, could explain behavioral performance for both carrier types across the full range of modulation frequencies studied (16-512 Hz). The results suggest that envelope synchrony in the budgerigar midbrain may underlie behavioral sensitivity to AM. Behavioral AM sensitivity based on synchrony in the budgerigar, which contrasts with rate-correlated behavioral performance in rabbits, raises the possibility that envelope synchrony, rather than average discharge rate, might also underlie AM perception in other species with sensitive AM detection abilities, including humans. These results highlight the importance of synchrony coding of envelope structure in the inferior colliculus. Furthermore, they underscore potential benefits of devices (e.g., midbrain implants) that evoke robust neural synchrony., (Copyright © 2016 the American Physiological Society.)

The subgroup J avian leukosis virus favors the myelocytic series cells and causes myeloid leukosis (myeloblastosis and myelocytomatosis). Natural cases of myeloblastosis (myeloblastic myeloid leukosis) are uncommon and usually occur in adult chickens. This paper describes clinical signs and gross and histopathologic features of myeloblastosis in an adult female budgerigar (Melopsittacus undulatus) that was infected naturally. At necropsy, the spleen was greatly enlarged (enlarged seven or eight times normal) while the other visceral organs were normal. Histologic examination of the spleen indicated a massive intravascular and extravascular accumulation of myeloblasts with a variable proportion of promyelocytes and myelocytes in the red pulp of the spleen.

The forkhead domain FOXP2 and FOXP1 transcription factors are implicated in several cognitive disorders with language deficits, notably autism, and thus play a central role in learned vocal motor behavior in humans. Although a similar role for FoxP2 and FoxP1 is proposed for other vertebrate species, including songbirds, the neurodevelopmental expression of these genes are unknown in a species with lifelong vocal learning abilities. Like humans, budgerigars (Melopsittacus undulatus) learn new vocalizations throughout their entire lifetime. Like songbirds, budgerigars have distinct brain nuclei for vocal learning, which include the magnocellular nucleus of the medial striatum (MMSt), a basal ganglia region that is considered developmentally and functionally analogous to Area X in songbirds. Here, we used in situ hybridization and immunohistochemistry to investigate FoxP2 and FoxP1 expression in the MMSt of juvenile and adult budgerigars. We found FoxP2 mRNA and protein expression levels in the MMSt that were lower than the surrounding striatum throughout development and adulthood. In contrast, FoxP1 mRNA and protein had an elevated MMSt/striatum expression ratio as birds matured, regardless of their sex. These results show that life-long vocal plasticity in budgerigars is associated with persistent low-level FoxP2 expression in the budgerigar MMSt, and suggests the possibility that FoxP1 plays an organizational role in the neurodevelopment of vocal motor circuitry. Thus, developmental regulation of the FoxP2 and FoxP1 genes in the basal ganglia appears essential for vocal mimicry in a range of species that possess this relatively rare trait., (© 2014 Wiley Periodicals, Inc.)

Vocal learning underlies acquisition of both language in humans and vocal signals in some avian taxa. These bird groups and humans exhibit convergent developmental phases and associated brain pathways for vocal communication. The transcription factor FoxP2 plays critical roles in vocal learning in humans and songbirds. Another member of the forkhead box gene family, FoxP1 also shows high expression in brain areas involved in vocal learning and production. Here, we investigate FoxP2 and FoxP1 mRNA and protein in adult male budgerigars (Melopsittacus undulatus), a parrot species that exhibits vocal learning as both juveniles and adults. To examine these molecules in adult vocal learners, we compared their expression patterns in the budgerigar striatal nucleus involved in vocal learning, magnocellular nucleus of the medial striatum (MMSt), across birds with different vocal states, such as vocalizing to a female (directed), vocalizing alone (undirected), and non-vocalizing. We found that both FoxP2 mRNA and protein expressions were consistently lower in MMSt than in the adjacent striatum regardless of the vocal states, whereas previous work has shown that songbirds exhibit down-regulation in the homologous region, Area X, only after singing alone. In contrast, FoxP1 levels were high in MMSt compared to the adjacent striatum in all groups. Taken together these results strengthen the general hypothesis that FoxP2 and FoxP1 have specialized expression in vocal nuclei across a range of taxa, and suggest that the adult vocal plasticity seen in budgerigars may be a product of persistent down-regulation of FoxP2 in MMSt., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Little is known about the normal bacterial flora of the skin of birds. To identify the bacterial organisms that reside on the integument of companion psittacine birds in a normal physiologic state, skin cultures were taken from 75 psittacine birds comprising 25 Congo African grey parrots ( Psittacus erithacus ), 25 budgerigars ( Melopsittacus undulatus ), and 25 cockatiels ( Nymphicus hollandicus ). All birds were adults and in good health with no underlying identifiable diseases, had not been on antibiotics in the preceding 2 months or longer, and had no skin or feather abnormalities. Cultures were taken from the axillary region and incubated on bovine blood agar plates. Positive cultures were identified for 52 out of 75 birds, and a total of 89 bacterial colonies grew. The most frequently identified bacterial organisms belonged to the genus Staphylococcus followed by Corynebacterium. Several other genera of bacteria were also isolated. Of the 89 bacterial colonies, 25 were identified to the species level and 50 to the genus level, and 14 were identified as either a nonfermenter or coliform.

Birds are generally thought to have excellent vision with high spatial resolution. However, spatial contrast sensitivity of birds for stationary targets is low compared to other animals with similar acuity, such as mammals. For fast flying animals body stability and coordination are highly important, and visual motion cues are known to be relevant for flight control. We have tested five budgerigars (Melopsittacus undulatus) in behavioural discrimination experiments to determine whether or not stimulus motion improves contrast sensitivity. The birds were trained to distinguish between a homogenous grey field and sine-wave gratings of spatial frequencies between 0.48 and 6.5 cyc/deg, and Michelson contrasts between 0.7% and 99%. The gratings were either stationary or drifting with velocities between 0.9 and 13 deg/s. Budgerigars were able to discriminate patterns of lower contrast from grey when the gratings were drifting, and the improvement in sensitivity was strongest at lower spatial frequencies and higher drift velocities. Our findings indicate that motion cues can have positive effects on visual perception of birds. This is similar to earlier results on human vision. Contrast sensitivity, tested solely with stationary stimuli, underestimates the sensory capacity of budgerigars flying through their natural environments., (Copyright © 2014 The Authors. Published by Elsevier Ltd.. All rights reserved.)