Persistent vocal learning in an aging open-ended learner reflected in neural FoxP2 expression.

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.

Lost companions: a new quill mite species and its possible coextinction with the Carolina parakeet.

Investigations of the parasites associated with extinct avian species provide unique insights into the ecology and evolution of both hosts and their parasitic counterparts. In the present paper, a new quill mite species, Peristerophila conuropsis sp. n., belonging to the family Syringophilidae (Prostigmata: Cheyletoidea) is described from the Carolina parakeet Conuropsis carolinensis Linnaeus (Psittaciformes: Psittacidae). This new species was collected from museum dry skin of the Carolina parakeet, the only native representative of the Psittacidae in the United States, which was an abundant resident of the southeastern and midwestern states and has been extinct in the beginning of the 20th century. Comment on the current taxonomic state and host associations of the genus Peristerophila are provided. Based on the host associations and habitats occupied by Peristerophila and related genera on parrots, it is hypothesized with the high probability that P. conuropsis has been extinct along with its host.

Pharmacokinetics of Trazodone in Hispaniolan Parrots (Amazona ventralis).

The objective of this study was to establish the pharmacokinetics of a single oral dose of trazodone in the Hispaniolan Amazon parrot (Amazona ventralis). Trazodone is a selective serotonin antagonist and reuptake inhibitor used commonly in both human and veterinary medicine as an antidepressant behavioral modification medicine. A single oral dose of compounded trazodone hydrochloride solution (20 mg/mL) at 50 mg/kg was administered to a total of 7 healthy adult Hispaniolan Amazon parrots. The 7 healthy adult parrots ranged in age from 10 to 15 years and weighed 228 to 323g. Blood was collected at baseline (2 weeks before study) and at 1, 2, 4, 6, 10, and 14 hours post-drug administration. Plasma concentrations of both trazodone and its active metabolite m-chlorophenylpiperazine (mCPP) were measured via liquid chromatography tandem mass spectrometry. Noncompartmental pharmacokinetic analysis was completed. The half-life (t1/2) ± SD of trazodone for the Hispaniolan parrots was 1.89 ± 0.49 hours, and the t1/2 ± SD of mCPP metabolite was 1.9 ± 0.55 hours. Maximum serum drug concentrations, or Cmax (ng/mL), were 738.3 ± 285.3 for trazodone. Times to achieve Cmax (hours) for trazadone and the mCPP metabolite were 1 hour and 2 hours postdosing, respectively. While this study did not establish the behavioral effects of trazodone, no adverse side effects were observed throughout the 48-hour period following drug administration and blood collection. Our results indicate that the oral administration of a 50-mg/kg single dose of trazodone to Hispaniolan parrots may be considered a safe dose. Plasma concentrations are comparable to previously published values in humans, dogs, horses, and pigeons (Columba livia domestica) for up to 14 hours following dosing. This study indicates that further studies are needed to establish the pharmacodynamics and the efficacy of trazodone in the medical management of behavioral problems in psittacine species.

Museomics and phylogenomics of lovebirds (Psittaciformes, Psittaculidae, Agapornis) using low-coverage whole-genome sequencing.

Natural history collections contain specimens that provide important insights into studies of ecology and evolution. With the advancement of high-throughput sequencing, historical DNA (hDNA) from museum specimens has become a valuable source of genomic data to study the evolutionary history of organisms. Low-coverage whole genome sequencing (WGS) has been increasingly applied to museum specimens for analyzing organelle genomes, but is still uncommon for genotyping the nuclear DNA fraction. In this study, we applied low-coverage WGS to phylogenomic analyses of parrots in the genus Agapornis by including both modern samples and historical specimens of âˆ¼100-year-old. Agapornis are small-sized African and Malagasy parrots with diverse characters. Earlier phylogenetic studies failed to resolve the positions of some key lineages, prohibiting a robust interpretation of the biogeography and evolution of these African parrots. Here, we demonstrated the use of low-coverage WGS for generating both mitochondrial and nuclear genomic data, and evaluated data quality differences between modern and historical samples. Our resolved Agapornis phylogeny indicates the ancestor of Agapornis likely colonized Madagascar from Australasia by trans-oceanic dispersal events before dispersing to the African continent. Genome-wide SNPs also allowed us to identify the parental origins of hybrid Agapornis individuals. This study demonstrates the potential of applying low-coverage WGS to phylogenomics and population genomics analyses and illustrates how including historical museum specimens can address outstanding questions regarding the evolutionary history of contemporary lineages.

Recent developments in parrot cognition: a quadrennial update.

Psittacines, along with corvids, are commonly referred to as 'feathered apes' due to their advanced cognitive abilities. Until rather recently, the research effort on parrot cognition was lagging behind that on corvids, however current developments show that the number of parrot studies is steadily increasing. In 2018, M. L. Lambert et al. provided a comprehensive review on the status of the most important work done so far in parrot and corvid cognition. Nevertheless, only a little more than 4 years after this publication, more than 50 new parrot studies have been published, some of them chartering completely new territory. On the 25th anniversary of Animal Cognition we think this warrants a detailed review of parrot cognition research over the last 4 years. We aim to capture recent developments and current trends in this rapidly expanding and diversifying field.

Social network analysis reveals context-dependent kin relationships in wild sulphur-crested cockatoos Cacatua galerita.

A preference to associate with kin facilitates inclusive fitness benefits, and increased tolerance or cooperation between kin may be an added benefit of group living. Many species exhibit preferred associations with kin; however, it is often hard to disentangle active preferences from passive overlap, for example caused by limited dispersal or inheritance of social position. Many parrots exhibit social systems consisting of pair-bonded individuals foraging in variably sized fission-fusion flocks within larger communal roosts of hundreds of individuals. Previous work has shown that, despite these fission-fusion dynamics, individuals can exhibit long-term preferred foraging associations outside their pair bonds. Yet the underlying drivers of these social preferences remain largely unknown. In this study, we use a network approach to examine the influence of kinship on social associations and interactions in wild, communally roosting sulphur-crested cockatoos, Cacatua galerita. We recorded roost co-membership, social associations and interactions in 561 individually marked birds across three neighbouring roosts. We then collected genetic samples from 205 cockatoos, and conducted a relationship analysis to construct a kinship network. Finally, we tested correlations between kinship and four social networks: association, affiliative, low-intensity aggression and high-intensity aggression. Our result showed that while roosting groups were clearly defined, they showed little genetic differentiation or kin structuring. Between roost movement was high, with juveniles, especially females, repeatedly moving between roosts. Both within roosting communities, and when visiting different roosts, individuals preferentially associated with kin. Supporting this, individuals were also more likely to allopreen kin. However, contrary to expectation, individuals preferred to direct aggression towards kin, with this effect only observed when individuals shared roost membership. By measuring social networks within and between large roosting groups, we could remove potential effects of passive spatial overlap on kin structuring. Our study reveals that sulphur-crested cockatoos actively prefer to associate with kin, both within and between roosting groups. By examining this across different interaction types, we further demonstrate that sulphur-crested cockatoos exhibit behavioural and context-dependent interaction rules towards kin. Our results help reveal the drivers of social association in this species, while adding to the evidence for social complexity in parrots.

Patterns of single limb forces during terrestrial and arboreal locomotion in rosy-faced lovebirds (Psittaciformes: Agapornis roseicollis).

The biomechanical demands of arboreal locomotion are generally thought to necessitate specialized kinetic and kinematic gait characteristics. While such data have been widely collected across arboreal quadrupeds, no study has yet explored how arboreal substrates influence the locomotor behavior of birds. Parrots - an ancient arboreal lineage that exhibit numerous anatomical specializations towards life in the trees - represent an ideal model group within which to examine this relationship. Here, we quantifiy limb loading patterns within the rosy-faced lovebird (Agapornis roseicollis) across a range of experimental conditions to define the circumstances under which arboreal gaits are triggered, and how, during arboreal walking, gait patterns change across substrates of varying diameter. In so doing, we address longstanding questions as to how the challenges associated with arboreality affect gait parameters. Arboreal locomotion was associated with the adoption of a sidling gait, which was employed exclusively on the small and medium diameter poles but not terrestrially. When sidling, the hindlimbs are decoupled into a distinct leading limb (which imparts exclusively braking forces) and trailing limb (which generates only propulsive forces). Sidling was also associated with relatively low pitching forces, even on the smallest substrate. Indeed, these forces were significantly lower than mediolateral forces experienced during striding on terrestrial and large diameter substrates. We propose that the adoption of sidling gaits is a consequence of avian foot morphology and represents a novel form of arboreal locomotion where inversion/eversion is impossible. Such movement mechanics is likely widespread among avian taxa and may also typify patterns of arboreal locomotion in humans.

Intra- and interspecific variation in self-control capacities of parrots in a delay of gratification task.

Forgoing immediate satisfaction for higher pay-offs in the future (delayed gratification) could be adaptive in situations that wild animals may encounter. To explain species-differences in self-control, hypotheses based on social complexity, feeding ecology, brain size and metabolic rate have been proposed. To explore these hypotheses in a comparative setting, we tested three macaw species (neotropical parrots)-great green macaws (N = 8), blue-throated macaws (N = 6), blue-headed macaws (N = 6)-and the distantly related African grey parrots (afrotropical parrots; N = 8) in a modified rotating tray task, in which subjects are required to inhibit consuming a constantly available low-quality reward in favour of a high-quality reward that becomes available only after an increasing delay (min. 5 s, max. 60 s). All four species successfully waited for a minimum of 8.3 s ± 11.7 s (group level mean ± SD) with African greys reaching a delay of 29.4 ± 15.2 s, and great green macaws-as best performing macaw species-tolerating delays of 20 s ± 8 s. The best performing African grey individual reached a maximum delay of 50 s, whereas, a great green and a blue-throated macaw tolerated a delay of 30 s max. Females tolerated higher maximum delays than males. Engaging in distraction behaviours enhanced waiting performance across species and all birds were able to anticipate the waiting duration. Our results suggest that both feeding and socio-ecological complexity may be a factor in self-control, but further systematically collected comparative data on self-control of different (parrot) species are required to test the evolutionary hypotheses rigorously.

Comments on "Intra- and interspecific variation in self-control capacities of parrots in a delay of gratification task".

Brucks (Anim Cogn 25(2):473-491, 2021) have published an intriguing paper on the differing abilities of various species of parrots to succeed in a delay of gratification task. I find their interspecies comparisons of considerable interest but take exception to their misrepresentation of prior research on delayed gratification from our laboratory in Koepke (J Comp Psychol 129:339-346, 2015). Contrary to their claims, our subject was never trained on the task; rather, one might argue instead that all their subjects received considerable training or at least forms of pre-exposure that could affect their overall claims. I also briefly discuss other design features that may have affected their results.

Effect of different injection rates and doses of contrast medium on the image quality of computed tomographic angiography in African grey parrots (Psittacus erithacus).

BACKGROUND: Atherosclerosis is a common cardiovascular disease in parrots but the antemortem diagnosis is challenging. In human medicine, computed tomography angiography (CTA) has been used widely for the diagnosis of atherosclerosis. By adjusting the injection rate and total dose of contrast medium, the image quality can be improved. To test the effects of different injection conditions on the image quality of major arteries, 10 African grey parrots (Psittacus erithacus) were used. Three injection rates (0.3, 0.4, 0.5 mL/s) and three doses (740, 370, 222 mg of iodine/bird) were tested while the other variables of the studies were fixed. RESULT: A higher injection dose led to a significantly higher attenuation, image noise and diameter, with a lower signal-to-noise ratio and contrast-to-noise ratio of the six major arteries. The 370 mg of iodine/bird group showed significantly better subjective image quality. Furthermore, with increasing injection rates, the prevalence of heterogeneity decreased. However, we found an increased risk of injection failure for the 0.5 mL/s groups. CONCLUSION: We recommend a combination of 370 mg of iodine/bird with 0.4 mL/s for clinical use to achieve better image quality for CTA.

Hematological and Plasma Biochemical Reference Values for Captive White-Fronted Parrots (Amazona albifrons) in México.

The objective of this study was to establish hematological and plasma biochemical reference values in captive white-fronted Amazon parrots (Amazona albifrons), as well as to determine whether sex effects the reference values. To our knowledge, hematological and plasma biochemical data have not been reported in this species. Thirty-seven clinically healthy adult individuals (21 males, 16 females) from El Nido Bird Sanctuary, Ixtapaluca, Estado de México, were the subject birds for this study. Complete blood count and selected plasma biochemical parameters, including uric acid, glutamate dehydrogenase, aspartate aminotransferase, total protein, and albumin, were evaluated. Blood samples were collected in the winter (January), outside of the birds' breeding season. Many hematological and plasma biochemical analytes had large coefficients of variation, and there were no statistically significant sex differences identified.

Nature calls: intelligence and natural foraging style predict poor welfare in captive parrots.

Understanding why some species thrive in captivity, while others struggle to adjust, can suggest new ways to improve animal care. Approximately half of all Psittaciformes, a highly threatened order, live in zoos, breeding centres and private homes. Here, some species are prone to behavioural and reproductive problems that raise conservation and ethical concerns. To identify risk factors, we analysed data on hatching rates in breeding centres (115 species, 10 255 pairs) and stereotypic behaviour (SB) in private homes (50 species, 1378 individuals), using phylogenetic comparative methods (PCMs). Small captive population sizes predicted low hatch rates, potentially due to genetic bottlenecks, inbreeding and low availability of compatible mates. Species naturally reliant on diets requiring substantial handling were most prone to feather-damaging behaviours (e.g. self-plucking), indicating inadequacies in the composition or presentation of feed (often highly processed). Parrot species with relatively large brains were most prone to oral and whole-body SB: the first empirical evidence that intelligence can confer poor captive welfare. Together, results suggest that more naturalistic diets would improve welfare, and that intelligent psittacines need increased cognitive stimulation. These findings should help improve captive parrot care and inspire further PCM research to understand species differences in responses to captivity.

Impairment of mixed melanin-based pigmentation in parrots.

Parrots and allies (Order Psittaciformes) have evolved an exclusive capacity to synthesize polyene pigments called psittacofulvins at feather follicles, which allows them to produce a striking diversity of pigmentation phenotypes. Melanins are polymers constituting the most abundant pigments in animals, and the sulphurated form (pheomelanin) produces colors that are similar to those produced by psittacofulvins. However, the differential contribution of these pigments to psittaciform phenotypic diversity has not been investigated. Given the color redundancy, and physiological limitations associated to pheomelanin synthesis, we hypothesized that the latter would be avoided by psittaciform birds. Here we test this by using Raman spectroscopy to identify pigments in feathers exhibiting colors suspicious of being produced by pheomelanin (i.e., dull red, yellow and grey- and green-brownish) in 26 species from the three main lineages of Psittaciformes. We detected the non-sulphurated melanin form (eumelanin) in black, grey and brown plumage patches, and psittacofulvins in red, yellow and green patches, but no evidence of pheomelanin. As natural melanins are assumed to be composed of eumelanin and pheomelanin in varying ratios, our results represent the first report of impairment of mixed melanin-based pigmentation in animals. Given that psittaciforms also avoid the uptake of circulating carotenoid pigments, these birds seem to have evolved a capacity to avoid functional redundancy between pigments, likely by regulating follicular gene expression. Ours study provides the first vibrational characterization of different psittacofulvin-based colors and thus helps to determine the relative polyene chain length in these pigments, which is related to their antireductant protection activity.

Problem-solving in a cooperative task in peach-fronted conures (Eupsittula aurea).

Cooperation is a complex behaviour found in many kinds of organisms and occurs between individuals of the same and different species. Several studies have examined the intentionality of this behaviour by testing the animals' understanding of the need for a partner when working in pairs. The mammalian species tested express such understanding, whereas most tested birds fail, especially when the test involves a delayed access to the setup by one of the co-operators. In the present study, the cooperative problem-solving capability of four peach-fronted conures (Eupsittula aurea) was investigated with the loose string test. All four parrots solved the paradigm by simultaneously pulling the ends of the same string to bring a platform with a food reward within reach. They were also capable of solving the task when one of the co-operators was delayed, even when visually isolated from each other. To further test their comprehension and to exclude the birds relying on task-associated cues, we video-recorded the trials and quantified possible cues and strategies for timing the pulling behaviour (e.g., sound of the partner's door when opening, sound of steps of partner approaching). The preferred cue to start pulling was to wait for their partner's arrival to the string. The number of vocalisations was significantly higher during visually isolated conditions and for successful trials compared to failed trials, suggesting possible information exchange. Our findings show that peach-fronted conures can solve a cooperative task, and that cooperation success is not determined by external cues or by partner identity or affinity.

Isolation and characterization of 15 new microsatellite markers for the globally endangered Lear's macaw Anodorhynchus leari.

A set of 16 microsatellite markers was characterized for Lear's macaw (Anodorhynchus leari) using DNA samples from captive individuals. Extending this molecular toolkit, including the use of samples from wild individuals, is expected to provide the required power of resolution for pedigree inference of both wild and captive individuals, and could support research on the genetic structure of wild populations. We characterize a set of 15 microsatellite markers optimized for the Lear's macaw, developed from a microsatellite-enriched library in a three-step procedure. Primer pairs were initially designed for 62 microsatellites with > 7 tandem repetitions. After amplification of DNA of five wild individuals from different localities, 22 loci seemed to be polymorphic and were further tested on 12 wild nestling samples. Fifteen unlinked loci showed unambiguous peaks and low to moderate polymorphism levels. The combination of the four most polymorphic markers allowed individual identification even of putative sibs.These markers complement previously described microsatellites developed for A. leari and constitute a fundamental genetic toolkit for the investigation of the genetics of both wild and captive populations, thus assisting integrated management plans for the conservation of this globally endangered species.

Cloacal Diseases in Companion Parrots: A Retrospective Study of 43 Cases (2012-2018).

Cloacal disease is considered a common presenting complaint in companion parrots. The purpose of this study was to better characterize the prevalence of cloacal disease within a population of owned psittacine birds. Medical records of all owned parrots presented to an exotic animal specialty service between July 2012 and January 2018 were retrospectively reviewed for the presence of cloacal disease. Cloacal disease was identified in 43 of 1137 cases (3.8%). Cockatoos presented with cloacal disease significantly more often than other psittacine groups (P < .001). Female parrots presented with cloacal disease significantly more often than males and unsexed birds (P < .001). Cockatoos with cloacal disease predominantly presented with prolapse of the cloaca itself (P = .006). There was no significant difference in outcome based on taxonomic group, sex, or primary cloacal pathology. Prospective studies with parrot species are encouraged to have an increased understanding of the behavioral and medical conditions that result in cloacal disease. These studies would hopefully facilitate the development of better treatment options for this relatively common disease presentation.

The multifactorial nature of beak and skull shape evolution in parrots and cockatoos (Psittaciformes).

BACKGROUND: The Psittaciformes (parrots and cockatoos) are characterised by their large beaks, and are renowned for their ability to produce high bite forces. These birds also possess a suite of modifications to their cranial architecture interpreted to be adaptations for feeding on mechanically resistant foods, yet the relationship between cranial morphology and diet has never been explicitly tested. Here, we provide a three-dimensional geometric morphometric analysis of the developmental and biomechanical factors that may be influencing the evolution of psittaciformes' distinctive cranial morphologies. RESULTS: Contrary to our own predictions, we find that dietary preferences for more- or less- mechanically resistant foods have very little influence on beak and skull shape, and that diet predicts only 2.4% of the shape variation in psittaciform beaks and skulls. Conversely, evolutionary allometry and integration together predict almost half the observed shape variation, with phylogeny remaining an important factor in shape identity throughout our analyses, particularly in separating cockatoos (Cacatuoidea) from the true parrots (Psittacoidea). CONCLUSIONS: Our results are similar to recent findings about the evolutionary trajectories of skull and beak shape in other avian families. We therefore propose that allometry and integration are important factors causing canalization of the avian head, and while diet clearly has an influence on beak shape between families, this may not be as important at driving evolvability within families as is commonly assumed.

Sperm morphology and evidence for sperm competition among parrots.

Sperm competition is an important component of post-copulatory sexual selection that has shaped the evolution of sperm morphology. Previous studies have reported that sperm competition has a concurrently directional and stabilizing effect on sperm size. For example, bird species that show higher levels of extrapair paternity and larger testes (proxies for the intensity of sperm competition) have longer sperm and lower coefficients of variation in sperm length, both within and between males. For this reason, these sperm traits have been proposed as indexes to estimate the level of sperm competition in species for which other measures are not available. The relationship between sperm competition and sperm morphology has been explored mostly for bird species that breed in temperate zones, with the main focus on passerine birds. We measured sperm morphology in 62 parrot species that breed mainly in the tropics and related variation in sperm length to life-history traits potentially indicative of the level of sperm competition. We showed that sperm length negatively correlated with the within-male coefficient of variation in sperm length and positively with testes mass. We also showed that sperm is longer in sexually dichromatic and in gregarious species. Our results support the general validity of the hypothesis that sperm competition drives variation in sperm morphology. Our analyses suggest that post-copulatory sexual selection is also important in tropical species, with more intense sperm competition among sexually dichromatic species and among species that breed at higher densities.

Development and characterization of novel microsatellite loci for the Blue-fronted Amazon (Amazona aestiva, Psittaciformes, Aves) and cross-species amplification for other two threatened Amazona species.

Parrots are among the most threatened avian groups of the world, with illegal pet trade being a major threat to some Amazon (Amazona genus) and macaw (Ara and Anodorhynchus genera) species. Population genetic studies and effective control of commercial breeders are important actions for the conservation of these parrot species; however, few microsatellite loci are available for most Amazona species to date. In this study, 25 polymorphic microsatellite loci were identified in silico and characterized for the Blue-fronted Amazon [Amazona aestiva (Aa)]. Loci were tested in 24 Blue-fronted Amazons from wild population from central Brazil with cross-species amplified in two individuals of Amazona vinacea (Av) and Amazona pretrei (Ap) from northeastern Minas Gerais and Rio Grande do Sul, in southeastern and south of Brazil, respectively. The number of alleles per locus for Aa ranged from 5 to 24 with an average of 13.1. Twenty-four and 25 loci were successfully amplified for Av and Ap, respectively. The observed and expected heterozygosities for Aa ranged from 0.27 to 1.00 and from 0.35 to 0.94, with averages of 0.75 and 0.85, respectively. Nine loci significantly deviated from Hardy-Weinberg equilibrium after Bonferroni correction (likely due to null alleles) and no significant linkage disequilibrium between loci pairs was detected. The combined paternity exclusion probability was very high, and the probability of identity was extremely low. This new set of microsatellite loci will be useful for analyzing population genetic structure and making conservation and management decisions, as well as for parentage analysis and the control of commercial breeding of Aa and potentially other Amazona species.

Budgerigars and zebra finches differ in how they generalize in an artificial grammar learning experiment.

The ability to abstract a regularity that underlies strings of sounds is a core mechanism of the language faculty but might not be specific to language learning or even to humans. It is unclear whether and to what extent nonhuman animals possess the ability to abstract regularities defining the relation among arbitrary auditory items in a string and to generalize this abstraction to strings of acoustically novel items. In this study we tested these abilities in a songbird (zebra finch) and a parrot species (budgerigar). Subjects were trained in a go/no-go design to discriminate between two sets of sound strings arranged in an XYX or an XXY structure. After this discrimination was acquired, each subject was tested with test strings that were structurally identical to the training strings but consisted of either new combinations of known elements or of novel elements belonging to other element categories. Both species learned to discriminate between the two stimulus sets. However, their responses to the test strings were strikingly different. Zebra finches categorized test stimuli with previously heard elements by the ordinal position that these elements occupied in the training strings, independent of string structure. In contrast, the budgerigars categorized both novel combinations of familiar elements as well as strings consisting of novel element types by their underlying structure. They thus abstracted the relation among items in the XYX and XXY structures, an ability similar to that shown by human infants and indicating a level of abstraction comparable to analogical reasoning.