Pachytene karyotypes of 17 species of birds

Background: To date less than 10% of bird species have been karyotyped. They are rather conservative with diploid chromosome numbers about 78-80 in most species examined. Immunostaining of meiotic chromosomes at pachytene stage enables more precise estimates of the number, morphology and variability of macro- and microchromosomes than conventional analysis of mitotic metaphase chromosomes does. Analysis of pachytene chromosomes led to discovery of germline-restricted chromosome (GRC) that was present in germline cells and absent in somatic cells in all 16 species of passerine birds examined. GRC has not been found in any non-passerine bird. Results: In this study, using immunolocalization of SYCP3, the main protein of the lateral elements of the synaptonemal complex (SC) and centromere proteins we examined male pachytene karyotypes of sixteen passerine species and one outgroup species the Common cuckoo Cuculus canorus and provided their idiograms and precise estimates of their diploid chromosome numbers and the numbers of chromosome arms. We provided the first description of the karyotypes of three species, corrected the published data on the karyotypes of ten species and confirmed them for four species. The pachytene cells of the Gouldian finch, Brambling and Common linnet contained heteromorphic bivalents indicating heterozygosity for inversions or centromere shifts. The European pied flycatcher, Gouldian finch and Domestic canary have extended centromeres in several macro- and microchromosomes. GRCs of various sizes and shapes were detected in all passerine species examined. Their chromatin was heavily labeled by anticentromere antibodies. The lateral elements of the GRC SC varied in their size from the largest to the smallest element of the pachytene karyotype. They also varied in shape from continuous to fragmented. Conclusions: All songbirds examined, except the Eurasian skylark, have highly conservative karyotypes, 2n=80-82+GRC with seven pairs of macrochromosomes and 33-34 pairs of microchromosomes. The interspecies differences concern the sizes of the macrochromosomes, morphology of the microchromosomes and sizes of the centromeres. GRC is present in all songbird species examined, varying in size, morphology and SC structure even between closely related species. This indicates its fast evolution.

Automated VHF-Radio Telemetry Reveals Resource-Driven Site Utilisation Patterns in a Small-Bodied, Highly Mobile Bird (Erythrura Gouldiae)

BackgroundInformation on site utilisation and movement is essential for managing species' resource requirements. Collecting these data requires frequent location sampling of multiple individuals, which can be challenging for small-bodied animals due to the often-large size of animal-borne satellite-based telemetry devices. We show how coded VHF-radio nano-transmitters and an array of passive receivers to collect location data at sufficient frequency and accuracy can be utilised to test whether the highly mobile and small-bodied Gouldian finch adheres to optimal foraging theory within a landscape of high spatiotemporal heterogeneity.MethodsCoded VHF-radio nano-transmitters (0.23 g wt.) were attached to 38 Gouldian finches (Erythrura gouldiae; < 12g bd. wt). Tagged birds were then detected by an array of 6 passive VHF-radio receivers (~ 530 m detection range) spread over 120 km2. We tracked the tagged birds during two sessions corresponding with high and low abundance of their primary food resource (Sorghum spp. seed). The mean and total duration that an individual spent within any receiver detection field (residence time) were used as dependants in a generalised linear mixed model approach within a Bayesian framework to assess the influence of tracking session, life stage, receiver site, and release site. Network analysis revealed the importance of specific areas for the finches within the receiver array using the proportional time a bird spent within any receiver's detection field and the movement between adjacent detection fields. ResultsThe daily mean and total duration that a tagged individual spent within a receiver detection field decreased by ~50% between periods of high and low seed availability, while the extent of movements across the landscape increased with a decline in seed resources. These data support the hypothesis that the Gouldian finch adheres to optimal foraging theory to survive periods of food scarcity. ConclusionsThe data collected via passive telemetry technology support the hypothesis that the Gouldian finch adheres to optimal foraging theory and uses alternative behavioural strategies to survive periods of food scarcity. Specifically, we found that Gouldian finches reduced the time spent foraging within a patch, increased the frequency of transit flights among patches, and expanded the size of their activity space as grass resources declined.

Morph Composition Matters in the Gouldian Finch (Chloebia gouldiae): Involvement of Red-Headed Birds Increases Vigilance

Animals invest in costly vigilance to detect threats. Joining groups reduces these costs, which can be further reduced in mixed-species assemblages. In colour-polymorphic species, morphs often experience different predation pressure and vary in a variety of traits. However, little is known about differences in vigilance or how group composition affects vigilance. The aim was to investigate whether higher conspicuousness increased vigilance and whether vigilance was reduced in mixed-morph groups like in mixed-species assemblages. I tested vigilance in the colour-polymorphic Gouldian Finch (Chloebia gouldiae). Same sex pairs of different age and of either pure (red-red or black-black) or mixed head colour were exposed to three contexts (familiar, changed and novel environment) and head movements were recorded. All birds reduced the frequency of head movements with increasing novelty, indicating different vigilance strategies (switching from a searching to a tracking strategy) depending on the situation. While vigilance did not differ between morphs, morph composition mattered. Black-headed pairs made fewer head movements than mixed-head colour pairs. Results indicated that conspicuousness did not affect vigilance, possibly due to existing adaptations to reduce predation risk. However, whenever red-headed birds were involved, vigilance increased either because of higher group conspicuousness or prevalence of aggression.

Individual Variation in Dietary Wariness Is Predicted by Head Color in a Specialist Feeder, the Gouldian Finch

Shifts in resource availability due to environmental change are increasingly confronting animals with unfamiliar food types. Species that can rapidly accept new food types may be better adapted to ecological change. Intuitively, dietary generalists are expected to accept new food types when resources change, while dietary specialists would be more averse to adopting novel food. However, most studies investigating changes in dietary breadth focus on generalist species and do not delve into potential individual predictors of dietary wariness and the social factors modulating these responses. We investigated dietary wariness in the Gouldian finch, a dietary specialist, that is expected to avoid novel food. This species occurs in two main head colors (red, black), which signal personality in other contexts. We measured their initial neophobic responses (approach attempts before first feed and latency to first feed) and willingness to incorporate novel food into their diet (frequency of feeding on novel food after first feed). Birds were tested in same-sex pairs in same and different head color pairings balanced across experiments 1 and 2. Familiar and novel food (familiar food dyed) were presented simultaneously across 5 days for 3 h, each. Gouldian finches fed on the familiar food first demonstrating food neophobia, and these latencies were repeatable. Birds made more approach attempts before feeding on novel than familiar food, particularly red-headed birds in experiment 1 and when partnered with a black-headed bird. Individuals consistently differed in their rate of incorporation of novel food, with clear differences between head colors; red-headed birds increased their feeding visits to novel food across experimentation equaling their familiar food intake by day five, while black-headed birds continually favored familiar food. Results suggest consistent among individual differences in response to novel food with red-headed birds being adventurous consumers and black-headed birds dietary conservatives. The differences in food acceptance aligned with responses to novel environments on the individual level (found in an earlier study) providing individuals with an adaptive combination of novelty responses across contexts in line with potential differences in movement patterns. Taken together, these novelty responses could aid in population persistence when faced with environmental changes.

Social niche construction in captive Gouldian Finch (Erythrura gouldiae) Flocks

The organization of animal groups is both a cause of, and consequence of, patterns of interactions among individuals. The stability of animal social organization reflects how individuals construct and maintain resilient patterns of interactions across changes in group size and membership. In this study we describe patterns of social interactions in captive flocks of Gouldian Finches (Erythrura gouldiae) that were exposed to changing social conditions. A flock of adult Gouldian Finches was exposed to two changing conditions, an introduction condition where juveniles were introduced to the flock, and a fission-fusion condition where the flock was split into two smaller flocks and a new group of juveniles introduced to each. We show that the social organization of captive Gouldian finch flocks is characterized by stable homophilic communities of adult females and juveniles. Females showed higher rates of approaches to other adult females, while juveniles maintined higher rates of approaches towards other juveniles. These findings highlight how the stable interactive decisions made by individuals contribute to higher-order patterns of organization in bird flocks. Furthermore, this study is one of the few to demonstrate self-assortment of juveniles in passerine flocks and suggests that peer and sibling interactions are an unexplored area in avian social development.

Metabolic rates of aggressive/submissive phenotypes are colour blind in the polymorphic Gouldian finch

Evidence from a number of species suggests behaviours associated with social rank are positively correlated with metabolic rate. These studies, however, are based on metabolic measurements of isolated individuals, thereby ignoring potential effects of social interactions on metabolic rates. Here, we characterised three pertinent metabolic indices in the two predominant genetic colour morphs of the Gouldian finch (Erythrura gouldiae): diurnal resting metabolic rate (RMR), nocturnal basal metabolic rate (BMR), and exercise-induced maximal metabolic rate (MMR). Research reveals red-headed morphs consistently dominate the less aggressive black-headed morphs and the two morphs to differ in other behavioural and physiological traits. We measured daytime RMR of intermorph naïve birds (first-year virgin males maintained in total isolation from opposite colour morphs) and their metabolic responses to viewing a socially unfamiliar bird of each colour. Subsequently each bird was placed in a home cage with an opposite colour morph (intermorph exposed) and the series of measurements repeated. Daytime RMR was indistinguishable between the two morphs, whether intermorph naïve or intermorph exposed. However, both red- and black-headed birds showed a greater short-term increase in metabolic rate when viewing an unfamiliar red-headed bird than when seeing a black-headed bird, but only when intermorph naïve. Measurements of BMR and exercise-induced MMR did not differ between the two morphs, and consequently aerobic scope was indistinguishable between them. We propose that the suite of behavioural differences between these two sympatric morphs are functionally complementary and represent evolutionary stable strategies permitting establishment of dominance status in the absence of metabolic costs.