Estrildid Research Articles

The modulation of social and non-social behavior by arginine vasotocin in the common waxbill, Estrilda astrild

The influence of the neuropeptide arginine vasotocin (AVT) has been demonstrated across various species, on an ample range of behaviors, yet the results appear to be highly species-specific. In this study, we aimed to test how AVT influences both social and non-social behaviors in the common waxbill Estrilda astrild, a highly social estrildid finch. Through a within-subject design study, we experimentally manipulated AVT pathways through muscular injections of both an agonist and an antagonist of AVT at different dosages, and performed competition over food tests to assess behavioral changes. Our observations reveal a decrease in birds' movements with both low and high dosages of AVT. Additionally, the higher AVT dosage led to a significant decrease in birds' feeding, aggressive behavior, and allopreening. Conversely, the lower AVT dosage increased the duration of allopreening, which is a proxy for affiliation. The use of Manning Compound, a V1a antagonist, did not produce any changes in behavior, however, the absence of affinity studies for this compound in birds makes it difficult to interpret these results. It is plausible that in common waxbills, AVT V1b or V1a receptors may be involved in regulating movement, feeding, aggressive behavior, and allopreening, rather than V2 AVT receptors.

Local resource availability drives habitat use by a threatened avian granivore in savanna woodlands.

Conserving threatened species relies on an understanding of their habitat requirements. This is especially relevant for granivorous birds, whose habitat use and movement patterns are intricately linked to the spatial and temporal availability of resources such as food and water. In this study, we investigated the habitat use, home range and daily activity patterns of the Endangered Southern Black-throated Finch (SBTF; Poephila cincta cincta) within a 75,000 ha savanna woodland study area in northeastern Australia. This semi-arid region is one of the key remaining strongholds for the species and is characterised by substantially different habitat and climatic conditions than areas where previous research on this species has been undertaken. We radio tracked 142 SBTF using both manual tracking and an array of 27 automated radio towers, which revealed a strong preference for eucalypt-dominated grassy woodland communities. The preference for these habitats also increased with decreasing distance to permanent water. While SBTF occupied large home ranges, individual SBTF were largely sedentary during the radio tracking period (21.8, range = 0.83-120 days), with few landscape-scale movements of more than 4.5 km. Daily foraging activity of SBTF exhibited bimodal peaks in the early morning and late afternoon, while other activities were greatest from the late morning to the early afternoon. Compared to other estrildid finches, our research suggests that SBTF track resources at a local scale across a large home range. We postulate that in times of resource scarcity SBTF may use dietary diversification, instead of landscape or regional-scale nomadic movements, to meet their resource needs. The species' movement patterns underscore the importance of local scale habitat management to facilitate resource availability throughout the year. Furthermore, our research helps target monitoring designs for granivorous birds that focus on the species' diurnal activity patterns.

A RETROSPECTIVE EVALUATION OF MORBIDITY AND MORTALITY IN ASSOCIATION WITH INFESTATION BY THE MITE STERNOSTOMA TRACHEACOLUM IN AN AVIARY-HOUSED POPULATION OF GOULDIAN FINCHES (CHLOEBIA GOULDIAE).

The Rhynonyssid mesostigmatic mite, Sternostoma tracheacolum, is a well-documented endoparasitic hematophagous arthropod of the respiratory tracts of multiple avian species, particularly Estrildid finches and canaries. In this retrospective study, 175 medical and 278 pathology records for the Gouldian finch (Chloebia gouldiae) population (N = 377) at the San Diego Zoo between 2013 and 2021 were analyzed to evaluate the effectiveness of ivermectin-based prophylaxis. A multivariable negative binomial regression model was constructed to evaluate the population effects of monthly treatments on morbidity or mortality associated with respiratory mites. While controlling for other factors in the model, the prophylactic treatment did not significantly reduce the monthly rate of mite-associated morbidity or mortality (IRR = 1.017, 95% CI: 0.997-1.036, P = 0.0759); however, low proportions of the population were prophylactically treated over time. Different factors were significant when separately evaluating adjusted associations with respiratory morbidity and mortality. The findings suggest increased rates of respiratory morbidity for each successive year of the study period (IRR = 1.180, 95% CI: 1.046-1.342, P = 0.0090) and increased rates of mite-associated mortality occurring annually between May and October (IRR = 1.697, 95% CI: 1.034-2.855, P = 0.0404) compared to the wet winter season. Our findings highlight the need to continually evaluate and optimize treatment regimens in zoological collections. Further investigations into this host-parasite relationship and potential treatments and preventive therapies are warranted.

Bird species richness and diversity responses to land use change in the Lake Victoria Basin, Kenya

The increasing demand for cultivated lands driven by human population growth, escalating consumption and activities, combined with the vast area of uncultivated land, highlight the pressing need to better understand the biodiversity conservation implications of land use change in Sub-Saharan Africa. Land use change alters natural wildlife habitats with fundamental consequences for biodiversity. Consequently, species richness and diversity typically decline as land use changes from natural to disturbed. We assess how richness and diversity of avian species, grouped into feeding guilds, responded to land use changes, primarily expansion of settlements and cultivation at three sites in the Lake Victoria Basin in western Kenya, following tsetse control interventions. Each site consisted of a matched pair of spatially adjacent natural/semi-natural and settled/cultivated landscapes. Significant changes occurred in bird species richness and diversity in the disturbed relative to the natural landscape. Disturbed areas had fewer guilds and all guilds in disturbed areas also occurred in natural areas. Guilds had significantly more species in natural than in disturbed areas. The insectivore/granivore and insectivore/wax feeder guilds occurred only in natural areas. Whilst species diversity was far lower, a few species of estrildid finches were more common in the disturbed landscapes and were often observed on the scrubby edges of modified habitats. In contrast, the natural and less disturbed wooded areas had relatively fewer estrildid species and were completely devoid of several other species. In aggregate, land use changes significantly reduced bird species richness and diversity on the disturbed landscapes regardless of their breeding range size or foraging style (migratory or non-migratory) and posed greater risks to non-migratory species. Accordingly, land use planning should integrate conservation principles that preserve salient habitat qualities required by different bird species, such as adequate patch size and habitat connectivity, conserve viable bird populations and restore degraded habitats to alleviate adverse impacts of land use change on avian species richness and diversity.

Pre-existing visual preference for white dot patterns in estrildid finches: a comparative study of a multi-species experiment.

The diverse characteristics of animal signal designs can be explained by the sensory bias hypothesis, which suggests that natural selection shapes sensory bias and preferences associated with signal design. Traditionally, this hypothesis has focused on female sensory biases and male sexual traits. However, considering shared sensory systems between males and females in non-sexual contexts, existing sensory bias possibly contributes to the evolution of shared social and sexual traits. Our previous studies on the family Estrildidae supported this idea. An evolutionary relationship probably existed between diet and white dot plumage, and a species of estrildid finches showed a visual preference for white dot patterns. To investigate this further, we examined hunger-related visual preferences using phylogenetic comparative methods and behavioural experiments. Specifically, we compared the gazing responses of 12 species of estrildids to monochromatic printed white dot and stripe patterns, considering their phylogenetic relationships. The results support our idea that the common estrildid ancestor had a hunger-related visual preference for white dot patterns. Subject species generally preferred white dots to stripes. Furthermore, males and females showed a similar preference towards dots. Our findings provide insights into the role of sensory bias in the evolution of mutual ornamentation.

Song system neuroanatomy, and immediate early gene expression in a finch species with extensive male and female song.

Birdsong is a relatively well-studied behavior, both due to its importance as a model for vocal production learning and as an intriguing complex social behavior. Until the last few decades, work on birdsong focused almost exclusively on males. However, it is now widely accepted that female song not only exists, but is fairly common throughout the oscine passerines. Despite this, and the large number of researchers who have begun exploring female song in the field, researchers in the lab have been slow to adopt model species with female song. Studying female song in the lab is critical for our understanding of sex-specific factors in the physiology controlling this fascinating behavior. Additionally, as a model for vocal production learning in humans, understanding the mechanistic and neuroendocrine control of female song is clearly important. In this study, we examined the red-cheeked cordon bleu (RCCB), an Estrildid finch species with extensive female song. Specifically, we found that there were no significant sex differences in circulating levels of testosterone and progesterone, nor in song production rate. There were no significant differences in cell densities in the three nuclei of the song control system we examined. Additionally, the volume of the robust nucleus of the arcopallium was not significantly different and we report the smallest sex difference in HVC yet published in a songbird. Finally, we demonstrated similar levels of motor driven immediate early gene expression in both males and females after song production.

Olfactory sex preferences in six Estrildid Finch species

Avian courtship behaviour is essential to attract potential mating partners. Courtship behaviours can involve displays of different sensory modes. Sex discrimination is a crucial step and in many bird species, sexes differ in acoustic and visual traits, allowing sex discrimination. It has been shown only recently that in some species of Estrildid Finches, chemical cues are involved in social communication. Here, we investigated whether olfaction also plays a role in sex discrimination in Estrildid Finches. Investigating olfactory sex preferences as an indicator behaviour in six different Estrildid Finch species, we aimed to understand whether sex- and/or species-specific differences in olfactory preferences exists and whether olfactory sex preferences correspond to species-specific differences in sex-specific acoustic and visual displays, e.g., singing, plumage dimorphisms and courtship dance. Olfactory sex preferences were tested in a Y-Maze test. We found differences in scent preferences among the different species of Estrildid Finches. We discussed the behavioural pattern with respect to other species-specific traits. And their potential implications in a broader mate choice context.

Seasonal variation in thermoregulatory capacity of three closely related Afrotropical Estrildid finches introduced to Europe

A species' potential geographical range is largely determined by how the species responds physiologically to its changing environment. It is therefore crucial to study the physiological mechanisms that species use to maintain their homeothermy in order to address biodiversity conservation challenges, such as the success of invasions of introduced species. The common waxbill Estrilda astrild, the orange-cheeked waxbill E. melpoda, and the black-rumped waxbill E. troglodytes are small Afrotropical passerines that have established invasive populations in regions where the climate is colder than in their native ranges. As a result, they are highly suitable species for studying potential mechanisms for coping with a colder and more variable climate. Here, we investigated the magnitude and direction of seasonal variation in their thermoregulatory traits, such as basal (BMR), summit (Msum) metabolic rates and thermal conductance. We found that, from summer to autumn, their ability to resist colder temperatures increased. This was not related to larger body masses or higher BMR and Msum, but instead, species downregulated BMR and Msum toward the colder season, suggesting energy conservation mechanisms to increase winter survival. BMR and Msum were most strongly correlated with temperature variation in the week preceding the measurements. Common waxbill and black-rumped waxbill, whose native ranges encompass the highest degree of seasonality, showed the most flexibility in metabolic rates (i.e., stronger downregulation toward colder seasons). This ability to adjust thermoregulatory traits, combined with increased cold tolerance, may facilitate their establishment in areas characterized by colder winters and less predictable climates.

The use of salt licks by birds in Peninsular Malaysia

Numerous wildlife species visit salt licks to consume soil (geophagy) or to drink water. Studies have mostly focused on salt lick use by mammals as they are easily identified owing to larger body size, predominance in using these resources, and predictable movement and behaviour, as well as several established hypotheses such as mineral supplementation. However, salt licks are also crucial to some birds. The interest in and documentation of avifaunal geophagy at salt licks have increased in recent years. However, few studies have investigated this phenomenon in Southeast Asia. We used camera traps to document bird species richness, diversity and encounter rates at 20 salt licks (nine natural and 11 artificial) within three reserves (the Royal Belum State Park, Perak and Krau Wildlife Reserve, Pahang, both primary forest, and secondary forest in Tembat Forest Reserve) in Peninsular Malaysia. We compared parameters between the two types of salt lick (natural and artificial) and two types of habitats (primary and secondary forest). We found that salt licks were used by 24 bird species, including pheasants, hornbills, rails, herons, doves, cuckoos, pittas, bulbuls, flycatchers, and estrildid finches. Raptors did not exhibit geophagous behaviour, except for the Brown Wood-Owl (Strix leptogrammica). Most salt lick users were resident carnivores and insectivores. The Asian Emerald Dove (Chalcophaps indica) and Red Junglefowl (Gallus gallus) were the most frequent birds at salt licks. Avian species richness in primary forests was similar for both types of salt licks, but species diversity was higher at natural salt licks. Meanwhile, species diversity at artificial salt licks was similar by habitat type, but bird’s species richness was significantly higher at primary forest artificial salt licks than at secondary forest artificial licks. Encounter rates of birds at artificial salt licks were higher than natural salt licks in primary forests. Furthermore, bird encounter rates at secondary forest artificial salt licks were higher than at primary forest artificial licks. We suggest that artificial salt licks can be used to enrich degraded forests since they serve a role similar to that of natural salt licks and can attract birds and other animals. This information is crucial to conservation and biodiversity management planning for protected forests, particularly secondary and degraded forests.

A comparison of nest-site characteristics for two sympatric Estrildid finches (Uraeginthus spp.) in Tanzania.

It is well known that birds have great diversity in nesting strategies, but we still have limited knowledge of the variation among species that share the habitat. Here, I will report and compare the nesting strategies between the two sympatric songbirds. Blue‐capped (Uraeginthus cyanocephalus) and red‐cheeked cordon‐bleus (Uraeginthus bengalus) are socially monogamous, biparental songbirds (family Estrildidae) that sympatrically inhabit arid landscapes with trees and bushes in East Africa. Both species build domed nests with grasses that are often located near wasp nests. They also sometimes take over old weaver (family Ploceidae) nests. While these nesting strategies are already described as common behavioral traits in both species in the literature, interspecies variation in these nesting strategies in areas of sympatry is not reported. My initial field observation during their breeding season suggested that whether these nesting strategies were adopted or not varied somewhat between the sympatric cordon‐bleus. Thus, I carried out a more formal investigation to test these differences. I found that red‐cheeked cordon‐bleus built their nests near wasp nests more frequently than blue‐capped cordon‐bleus, while I did not find any other significant differences between the nesting sites of the two species, such as the use of weaver nests, the types of nesting plants, or nest heights. These results suggest that the sympatric cordon‐bleus share several nest‐site characteristics, but that red‐cheeked cordon‐bleus have an affinity for nesting near wasp nests. Further studies will be required to elucidate the costs and benefits of these nesting strategies or the role that adjacency to wasp nests might play in the sympatry of the two species.

Description of Staphylococcal Strains from Straw-Coloured Fruit Bat (Eidolon helvum) and Diamond Firetail (Stagonopleura guttata) and a Review of their Phylogenetic Relationships to Other Staphylococci.

The phylogenetic tree of the Staphylococcus aureus complex consists of several distinct clades and the majority of human and veterinary S. aureus isolates form one large clade. In addition, two divergent clades have recently been described as separate species. One was named Staphylococcus argenteus, due to the lack of the “golden” pigment staphyloxanthin. The second one is S. schweitzeri, found in humans and animals from Central and West Africa. In late 2021, two additional species, S. roterodami and S. singaporensis, have been described from clinical samples from Southeast Asia. In the present study, isolates and their genome sequences from wild Straw-coloured fruit bats (Eidolon helvum) and a Diamond firetail (Stagonopleura guttata, an estrildid finch) kept in a German aviary are described. The isolates possessed staphyloxanthin genes and were closer related to S. argenteus and S. schweitzeri than to S. aureus. Phylogenetic analysis revealed that they were nearly identical to both, S. roterodami and S. singaporensis. We propose considering the study isolates, the recently described S. roterodami and S. singaporensis as well as some Chinese strains with MLST profiles stored in the PubMLST database as different clonal complexes within one new species. According to the principle of priority we propose it should be named S. roterodami. This species is more widespread than previously believed, being observed in West Africa, Southeast Asia and Southern China. It has a zoonotic connection to bats and has been shown to be capable of causing skin and soft tissue infections in humans. It is positive for staphyloxanthin, and it could be mis-identified as S. aureus (or S. argenteus) using routine procedures. However, it can be identified based on distinct MLST alleles, and “S. aureus” sequence types ST2470, ST3135, ST3952, ST3960, ST3961, ST3963, ST3965, ST3980, ST4014, ST4075, ST4076, ST4185, ST4326, ST4569, ST6105, ST6106, ST6107, ST6108, ST6109, ST6999 and ST7342 belong to this species.

Germline-restricted chromosome shows remarkable variation in size among closely related passerine species.

Passerine birds have a supernumerary chromosome in their germ cells called the germline-restricted chromosome (GRC). The GRC was first discovered more than two decades ago in zebra finch but recent studies have suggested that it is likely present in all passerines, the most species rich avian order, encompassing more than half of all modern bird species. Despite its wide taxonomic distribution, studies on this chromosome are still scarce and limited to a few species. Here, we cytogenetically analyzed the GRC in five closely related estrildid finch species of the genus Lonchura. We show that the GRC varies enormously in size, ranging from a tiny micro-chromosome to one of the largest macro-chromosomes in the cell, not only among recently diverged species but also within species andsometimes even between germ cells of a single individual. In Lonchura atricapilla, we also observed variation in GRC copy number among male germ cells of a single individual. Finally, our analysis of hybrids between two Lonchura species with noticeably different GRC size directly supported maternal inheritance of the GRC. Our results reveal the extraordinarily dynamic nature of the GRC, which might be caused by frequent gains and losses of sequences on this chromosome leading to substantial differences in genetic composition of the GRC between and even within species. Such differences might theoretically contribute to reproductive isolation between species and thus accelerate the speciation rate of passerine birds compared to other bird lineages.

Germline-Restricted Chromosome (GRC) in Female and Male Meiosis of the Great Tit (Parus major, Linnaeus, 1758).

All songbirds studied so far have a germline-restricted chromosome (GRC), which is present in the germ cells and absent in the somatic cells. It shows a wide variation in size, morphology, and genetic content between the songbird species. In this paper, we analyzed GRC behavior in female and male meiosis of the great tit, using immunolocalization of meiotic proteins and FISH with GRC-derived DNA probes. We found that, despite dozens of million years of independent evolution, the great tit GRC displays a striking similarity with the GRCs of two species of martins and two species of estrildid finches examined earlier. It was usually present in two copies in females forming recombining bivalent and in one copy in males forming a condensed heterochromatic body with dotted-like axial elements of the synaptonemal complex. We observed mosaicism for the GRC copy number in the female and male great tit. This indicates that one of the GRC copies might be passively lost during premeiotic germ cell divisions. After the meiotic prophase, the GRC was ejected from most male germ cells. The reverse and interspecies FISH with GRC-specific microdissected DNA probes indicates that GRCs of the great tit, pale martin, and zebra finch differ substantially in their genetic content despite similarities in the meiotic behavior.

Context‐sensitive dance–vocal displays affect song patterns and partner responses in a socially monogamous songbird

AbstractMultimodal signaling contributes to efficient communication by improving signal efficacy and increasing signal information. Songbirds often combine dance displays with songs according to the socio‐sexual context; therefore, the song is assumed to function differently depending on dance displays. In this study, we tested how dance displays affect song patterns and the responses of paired partners using male and female blue‐capped cordon‐bleus (Uraeginthus cyanocephalus). Blue‐capped cordon‐bleus are a socially monogamous estrildid finch, and both males and females perform songs and distinct “tap dance”‐like displays. Songs with dance displays were longer and more stereotyped than songs without dance displays in both males and females. Furthermore, both male and female paired partners showed more gestural responses to songs with dance displays than those without dance displays. Songs without dance displays were performed under both isolated and paired conditions, whereas songs with dance displays were only performed when the focal bird was housed with a paired partner. These results suggest that songs had different functions depending on dance displays and social contexts. The multimodal display of blue‐capped cordon‐bleus seems to draw the attention of paired partners to the physical abilities of the performer.

Usutu virus infection in aviary birds during the cold season

ABSTRACT The mosquito-borne flavivirus Usutu virus (USUV) is responsible for countless deaths in both resident populations and birds kept in outdoor aviaries. Since 2001, USUV outbreaks have attracted increased attention due to the rapid geographical spread of the virus and its close relationship to West Nile virus (WNV), an emerging pathogen in humans and animals. Similar to WNV, the USUV enzootic transmission cycle predominantly involves Culex spp. as vectors, whereas birds serve as amplifying reservoir hosts. In Europe, USUV-associated disease outbreaks in birds are almost exclusively described during late spring and early autumn (early April to late October). Contagiousness of virus particles excreted by infected birds has not yet been proven, so that the role of non-vector-borne transmission, as it is known for the closely related WNV, remains unclear. Here we report the diagnosis of USUV infection in 15 of 24 birds from mortality outbreaks that occurred during the cold season between late October 2018 and early April 2019, in eight different aviaries located in Germany. Detection of USUV was performed using standardized molecular biological methods and immunohistochemistry for verification of the infection. USUV infection in a parrot species, a tropical finch and two estrildid finches are reported for the first time. Further research on the occurrence of USUV infection during the cold season is key to understanding the dynamics of viral transmission as well as for a profound health risk assessment for aviary birds as well as humans.

Like Father Like Son: Cultural and Genetic Contributions to Song Inheritance in an Estrildid Finch.

Social learning of vocalizations is integral to song inheritance in oscine passerines. However, other factors, such as genetic inheritance and the developmental environment, can also influence song phenotype. The relative contributions of these factors can have a strong influence on song evolution and may affect important evolutionary processes such as speciation. However, relative contributions are well-described only for a few species and are likely to vary with taxonomy. Using archived song data, we examined patterns of song inheritance in a domestic population of Java sparrows (Lonchura oryzivora), some of which had been cross-fostered. Six-hundred and seventy-six songs from 73 birds were segmented and classified into notes and note subtypes (N = 22,972), for which a range of acoustic features were measured. Overall, we found strong evidence for cultural inheritance of song structure and of the acoustic characteristics of notes; sons’ song syntax and note composition were similar to that of their social fathers and were not influenced by genetic relatedness. For vocal consistency of note subtypes, a measure of vocal performance, there was no apparent evidence of social or genetic inheritance, but both age and developmental environment influenced consistency. These findings suggest that high learning fidelity of song material, i.e., song structure and note characteristics, could allow novel variants to be preserved and accumulate over generations, with implications for evolution and conservation. However, differences in vocal performance do not show strong links to cultural inheritance, instead potentially serving as condition dependent signals.

The Gut Microbial Composition Is Species-Specific and Individual-Specific in Two Species of Estrildid Finches, the Bengalese Finch and the Zebra Finch.

Microbial communities residing in the gastrointestinal tracts of animals have profound impacts on the physiological processes of their hosts. In humans, host-specific and environmental factors likely interact together to shape gut microbial communities, resulting in remarkable inter-individual differences. However, we still lack a full understanding of to what extent microbes are individual-specific and controlled by host-specific factors across different animal taxa. Here, we document the gut microbial characteristics in two estrildid finch species, the Bengalese finch (Lonchura striata domestica) and the zebra finch (Taeniopygia guttata) to investigate between-species and within-species differences. We collected fecal samples from breeding pairs that were housed under strictly controlled environmental and dietary conditions. All individuals were sampled at five different time points over a range of 120 days covering different stages of the reproductive cycle. We found significant species-specific differences in gut microbial assemblages. Over a period of 3 months, individuals exhibited unique, individual-specific microbial profiles. Although we found a strong individual signature in both sexes, within-individual variation in microbial communities was larger in males of both species. Furthermore, breeding pairs had more similar microbial profiles, compared to randomly chosen males and females. Our study conclusively shows that host-specific factors contribute structuring of gut microbiota.

Potential role of sensory bias in plumage pattern evolution: termite-eating and polka-dots in estrildid finches

Conspicuous colour patterns of animals, such as dots or stripes, can function as sexual and/or social signals. Their evolution is often explained by honest indicator mechanisms or the sensory exploitation hypothesis. In birds, however, the latter scenario has been scarcely tested. According to the sensory exploitation hypothesis, prey-like colour patterns can evolve when they contribute to attracting opposite-sex conspecifics by hitchhiking pre-existing sensory systems (sensory bias) that help foraging. Even without cheating scenarios, visual systems can serve as an underlying factor that facilitates the evolution of both foraging behaviours and colour patterns on the body. To test this idea, we examined the relationship between bird plumage patterns and diet using phylogenetic comparative approaches. Specifically, we focused on white polka-dot plumage patterns in estrildid finches and tested whether such patterns evolved for visual sensory systems that help foraging termites and other gregarious whitish small round prey items. Although we predicted that white polka-dots exist in termite-eater species, and that termite-eating evolved before the white polka-dot pattern, ancestral reconstruction did not reveal clear ancestral states for termite-eating. However, the phylogenetic regression model showed that species with conspicuous white polka-dots tended to be termite-eaters. We also found that estrildids with white polka-dots were likely to become termite-eaters, while those without white polka-dots were likely to become non-termite eaters, according to evolutionary transition analysis. These results are in contrast to the prediction of sensory exploitation hypothesis, wherein diet is believed to trigger the evolution of plumage patterns. However, the results presented here suggest that pre-existing sensory bias for white dots may have promoted the evolution of both termite-eating and white polka-dot plumage patterns in estrildids.

Biased Learning of Sexual Signals by Female Bengalese Finches

Peak shift in mate preference learning can be a driver of rapid repeated speciation. Therefore, clades that have undergone recent adaptive radiations are predicted to show biased learning of signals from the opposite sex. The estrildid finches are one such clade. In species including the Zebra Finch Taeniopygia guttata and the Bengalese Finch Lonchura striata var. domestica, females choose mates in part based on their songs. Consistent with theory, female Zebra Finches show peak shift in their learned response to male song characteristics. We used operant conditioning to train female Bengalese Finches to respond to songs with trills of one length and to ignore songs with trills of another length. Then, we exposed those females to songs with a range of trill lengths, and we observed their responses. We found that at least some Bengalese Finches also show behaviour consistent with peak shift in their response to male songs. Moreover, females evaluated songs relative to other songs they had recently heard. Our results suggest that females respond to male sexual signals with bias in multiple species in the rapidly speciating estrildid clade.

Germline-restricted chromosome (GRC) in the sand martin and the pale martin (Hirundinidae, Aves): synapsis, recombination and copy number variation

All songbirds studied to date have an additional Germline Restricted Chromosome (GRC), which is not present in somatic cells. GRCs show a wide variation in genetic content and little homology between species. To check how this divergence affected the meiotic behavior of the GRC, we examined synapsis, recombination and copy number variation for GRCs in the closely related sand and pale martins (Riparia riparia and R. diluta) in comparison with distantly related estrildid finches. Using immunolocalization of meiotic proteins and FISH with GRC-specific DNA probes, we found a striking similarity in the meiotic behavior of GRCs between martins and estrildid finches despite the millions of years of independent evolution. GRCs are usually present in two copies in female and in one copy in male pachytene cells. However, we detected polymorphism in female and mosaicism in male martins for the number of GRCs. In martin and zebra finch females, two GRCs synapse along their whole length, but recombine predominately at their ends. We suggest that the shared features of the meiotic behavior of GRCs have been supported by natural selection in favor of a preferential segregation of GRCs to the eggs.