Estrilda Astrild 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.

Seasonal variations in the structure of avian community in Zambezi riparian forest

Among the different biomes in southern Africa, tropical riparian forests appear to be especially rich in terms of biodiversity, but little is known about avian communities occupying these forests. In this paper, bird counts were conducted in May, July–August, and October–November in 2013 and 2014. The line transect method was used. A transect 16.6 km long was designed along the Zambezi River between S 17.4975 E 24.3478 and S 17.4874 E 24.447. In total, 146 bird species were recorded. The number of species detected each season varied from 95 to 100. The number of dominant species was consistently low, varying between 2 and 3 depending on the month. However, the cumulative dominance and the dominance index were much higher in the dry season (May–August) than in the wet season (October–November). Two species were dominant each month: Euplectes axillaris and Pycnonotus tricolor. Vidua macroura and Estrilda astrild were dominant only in October, while Streptopelia capicola was dominant only in May. The group of subdominants was much more diverse than dominants and included 13 species. The Shannon diversity index increased between July and November from 3.45 to 4.05 but Simpson's diversity index did not show any seasonal trend. Pielou's evenness index was higher in the wet season (0.82–0.88) than in the dry season (0.76–0.79). The proportions of the main feeding guilds were much the same throughout the year, except for November, when the proportion of insectivores markedly increased, while that of granivores decreased. Riparian forest corridors in urbanized environments may be viewed as main instruments for offsetting the negative effects of habitat loss and fragmentation. Dataset published through GBIF (DOI: 10.15470/0ssr1v)

Multiple effects of weather on common waxbill group foraging and social behavior

Abstract The weather poses challenges for wildlife. Environmental challenges can be responded to at the group level by social animals, but the influence of weather on group behavior is poorly understood. We investigated how weather affects behavior in a gregarious species by monitoring common waxbills (Estrilda astrild) in a large mesocosm during 5 yr. We found seasonal patterns in collective foraging, aggressiveness, and the structure of the social network, usually showing 2 cycles per year: one peaking in Spring and a smaller one peaking in late Summer. Controlling for seasonality, we found behavioral changes related to increased energy demands in colder and/or cloudier days, such as more frequent and larger foraging groups that resulted in less-structured social networks. Rain and wind disturb movement, and we found that, on rainy days, foraging group journeys became briefer and more synchronous, resulting in stronger associations between individuals and less-structured networks, and that on windy days foraging groups were less frequent, larger, and with more within-group aggression. The results show that the weather has more varied effects than anticipated on ecologically relevant group behavior. We discuss how such weather-related effects can improve predictions of how social animals will react to environmental changes.

Behavioural lateralization covaries with sex and inhibitory control in the common waxbill

Behavioural lateralization covaries with sex and inhibitory control in the common waxbill

Dietary tryptophan affects group behavior in a social bird

Abstract The amino acid tryptophan (Trp) is a precursor of the neurotransmitter serotonin. Trp supplementation or other forms of serotonergic enhancement generally promote pro-social behavior, decreasing aggression, and also feeding in different animals. However, past research has been conducted in confined spaces, and there is little work in naturalistic conditions where animals move and associate more freely. We gave a Trp-enriched diet to a free-flying flock of common waxbills (Estrilda astrild) in semi-natural conditions and monitored group foraging, aggressions during feeding, and the social network. Contrary to expectations, aggressiveness and feeding increased during Trp supplementation. Consistent with the prediction of increased social associations, foraging groups became larger, and individuals joined more foraging groups, but these changes appear driven by increased appetite during Trp treatment. Also, the mean strength of associations in the social network did not change. Overall, Trp supplementation affected group behavior in this free-flying flock, but mostly in directions unanticipated based on research conducted in small spaces. To harmonize our results with those found in small confined spaces, we hypothesize that free-flying birds have energetic requirements not experienced in lab-housed individuals, which may impact social behavior and responses to Trp.

Provisional atlas of breeding birds of Walvis Bay in the coastal Namib Desert


 
 
 In austral summer 2016/17, a provisional bird atlas project was conducted in the town of Walvis Bay (~260 ha), Namibia. In total, 18 breeding bird species were recorded. Four eudominant species (Cape Sparrow, Rock Dove, Laughing Dove, and Common Waxbill) comprised together 65.2% of all breeding birds. Three dominant species – House Sparrow, Southern Masked Weaver, and Speckled Pigeon – comprised additional 23.0%. The community dominance index (DI) was = 0.40, Shannon’s Diversity Index H’ = 2.21, Simpson’s Diversity Index D = 0.87, and Pielou’s Evenness Index J’ = 0.76. By far the most numerous feeding guild were granivores (88.0% of all birds recorded) followed by insectivores (6.0%) and frugivores (5.3%). Tree and/or shrub nesting birds comprised 59.5%, while birds nesting in/on buildings the remaining 40.5%. There were neither ground-nesting nor holenesting birds. Structure-wise, the avian community in the town resembles avian communities in other parts of the world (strong dominance of granivores, such as sparrows and doves). In austral summer 2018/19, a total of 25 marine species were recorded in the lagoon, of which nine (36%) were Palearctic migrant and 16 (64%) African residents. In terms of the number of individuals, Palearctic migrants constituted 17% and African residents 83%. More than half of all marine birds were Greater Flamingos, while the most numerous Palearctic species was the Curlew Sandpiper.
 
 

Phenotypic associations of common waxbill gut and feather microbiome diversity in a shared environment

Abstract Microbial diversity may affect host phenotypes, including morphology and behaviour, but it remains unclear to which extent those could be mediated by host differences in diet or habitat use. We used a population of wild common waxbills living in a large open-air mesocosm to control for such differences and test whether phenotypic variation is associated with cloaca bacteria diversity. We also tested correlations between feather-associated bacteria diversity and plumage colour ornamentation. Albeit weakly correlated, individuals sharing more similar cloaca microbiotas were more similar in their carotenoid-based plumage and bill red colour, suggesting that the gut microbiota can influence ornamentation even when individuals are in the same habitat and have access to the same food resources, perhaps mediating individual differences in feeding or digestion. There were no associations between feather bacteria and plumage colour, nor between cloaca bacteria and body size or several behavioural phenotypes. These results further highlight that investigating associations between microbiota and behaviour in nature should account for variation in extrinsic factors.

Biophysical models accurately characterize the thermal energetics of a small invasive passerine bird

Effective management of invasive species requires accurate predictions of their invasion potential in different environments. By considering species' physiological tolerances and requirements, biophysical mechanistic models can potentially deliver accurate predictions of where introduced species are likely to establish. Here, we evaluate biophysical model predictions of energy use by comparing them to experimentally obtained energy expenditure (EE) and thermoneutral zones (TNZs) for the common waxbill Estrilda astrild, a small-bodied avian invader. We show that biophysical models accurately predict TNZ and EE and that they perform better than traditional time-energy budget methods. Sensitivity analyses indicate that body temperature, metabolic rate, and feather characteristics were the most influential traits affecting model accuracy. This evaluation of common waxbill energetics represents a crucial step toward improved parameterization of biophysical models, eventually enabling accurate predictions of invasion risk for small (sub)tropical passerines.

Social network positions of common waxbills are resilient to prolonged absence and to manipulation of ornamental plumage

Social network positions of common waxbills are resilient to prolonged absence and to manipulation of ornamental plumage

Bullying as an advertisement of social dominance in common waxbills.

Bullying consists of preferentially attacking individuals lowest in the dominance hierarchy, and its functions are unclear because the most subordinate individuals do not pose social challenges to the aggressor. Instead, conflict is expected mostly between individuals of similar dominance rank or socially distant (i.e. weakly associated), among whom dominance relationships may not be well established. A possible function of bullying is that it may be used as a low-risk strategy of showing-off dominance to relevant third parties. To study this hypothesis, we monitored aggressions during feeding, the composition of audiences, dominance hierarchy and social network of common waxbills (Estrilda astrild) in an open-air mesocosm, and tested (i) whether their aggressions show a pattern of bullying, and (ii) whether audience effects influence aggressiveness. Waxbills showed bullying, most often attacking the lowest ranking individuals rather than socially distant individuals or those of similar dominance rank, and aggressions increased when the audience included socially distant individuals, indicating a signalling function of bullying. Showing-off dominance in the presence of socially distant individuals may be a strategy to manage dominance hierarchies, avoiding direct fights with potentially dangerous opponents in the audience. We suggest that bullying is a safe manner of managing dominance hierarchies, by signalling dominance status to potential opponents.

Effects of mesotocin manipulation on the behavior of male and female common waxbills

The oxytocin family of neuropeptides is implicated in the regulation of sociality across vertebrates. Non-mammalian homologs of oxytocin, such as isotocin in fish and mesotocin in amphibians, reptiles and birds, all play crucial roles modulating social and reproductive behavior. In this study, we exogenously manipulated the mesotocinergic system in a highly social bird, the common waxbill Estrild astrild, and tested the effects on affiliative and aggressive behavior by performing tests of competition over food. Birds treated with mesotocin decreased almost all the behaviors we studied (movement, feeding, allopreening), while birds treated with an oxytocin antagonist showed a reduction only in social behaviors (aggressions and allopreening). We also found two sex-specific effects: mesotocin reduced allopreening more in males than females, and the oxytocin antagonist reduced aggressiveness only in females. Our results suggest sex-specific effects in the modulation of affiliative and aggressive behaviors via mesotocinergic pathways.

The role of serotonin in modulating common waxbill behaviour

Serotonin or 5-hydroxytryptamine (5-HT) is a monoaminergic neurotransmitter that is known to influence behaviour in various animal species. Its actions, however, are complex and not well-understood yet. Here, we tested whether and how two 5-HT receptor agonists and a 5-HT receptor antagonist influence behaviour in common waxbills (Estrilda astrild), focusing on aggression, movement and feeding. We applied acute administration of either 8-OH-DPAT (a 5-HT1A receptor agonist), fluoxetine (a selective serotonin reuptake inhibitor; SSRI) or WAY 100,635 (a 5-HT1A receptor antagonist), and then quantified behaviour in the context of competition for food. Waxbills treated with the SSRI fluoxetine showed an overall decrease of aggressive behaviour, activity and feeding, while we found no significant effects of treatment with the other serotonergic enhancer (8-OH-DPAT) or with the antagonist WAY 100,635. Since both 8-OH-DPAT and WAY 100,635 act mainly on 5-HT1A receptor pathways, while fluoxetine more generally affects 5-HT pathways, our results suggest that receptors other than 5-HT1A are important for serotonergic modulation of waxbill behaviour.Significance statementThe serotonergic system is of interest for current behavioural research due to its influence on a range of behaviours, including aggression, affiliative behaviour, feeding and locomotion in various species. There are, however, numerous discrepancies regarding the behavioural effects of serotonin across studies. We used acute pharmacological manipulations of the serotonergic system in common waxbills, using two serotonin enhancers (8-OH-DPAT and fluoxetine) and a serotonin blocker (WAY 100,635). Behavioural effects of these pharmacological manipulations on aggressiveness, movement and feeding, during tests of competition over food, indicated an anxiogenic-like effect of fluoxetine, but not of 8-OH-DPAT and WAY 100,635. This suggests a distinct role for different serotonergic pathways on waxbill behaviour.

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.

Avian malaria, haematocrit, and body condition in invasive wetland passerines settled in southwestern Spain

Avian malaria and related haemosporidian parasites can negatively impact fitness in many songbirds. Research on the malaria infection and its physiological costs on their avian hosts is heavily skewed toward native passerines, with exotic species underrepresented. However, introduced species may carry on and spread new pathogens to native species, and play a role on parasite transmission cycle in invaded bird communities as pathogen reservoir. Here, we molecularly assess the prevalence and diversity of haemosporidian parasites in three introduced wetland passerines (the Red Avadavat Amandava amandava, the Yellow-crowned Bishop Euplectes afer, and the Common Waxbill Estrilda astrild) captured during the same season in southwestern Spain. We also explored the relation between parasite infection, body condition, haematocrit, and uropygial gland volume. We detected an overall parasite prevalence of 3.55%, where Common Waxbills showed higher prevalence (6.94%) than Red Avadavats (1.51%). None Yellow-crowned Bishops were infected with haemosporidians. Almost 60% of infections were caused by Leucocytozoon, and about 40% by Plasmodium. We identified four unique lineages of Plasmodium and three of Leucocytozoon. Moreover, 91% of the identified host–parasite interactions represented new host records for these haemosporidian parasites. Parasite infection was not related to body condition, haematocrit, and uropygial gland volume of the wetland passerines. Haematocrit values varied seasonally among bird species. Additionally, haematocrit was positively related to body condition in the Yellow-crowned Bishops, but not in the other species. Red Avadavats had higher haematocrit levels than Yellow-crowned Bishops, whereas Common Waxbills showed the lower haematocrit values. The uropygial gland volume was positively correlated with body condition in all bird species. Common Waxbills showed higher uropygial gland volumes related to their body size than birds from other two species. These outcomes highlight the importance of exotic invasive species in the transmission dynamics of haemosporidian parasites.

Domed nests as an exaptation for compound nest construction: the case of the common waxbill

Domed nests as an exaptation for compound nest construction: the case of the common waxbill

Oestradiol reduces female bill colour in a mutually ornamented bird.

Carotenoid-based colour signals can be costly to produce and maintain, and trade-offs between signalling and other fitness traits are expected. In mutually ornamented species, trade-offs with reproduction may be stronger for females than males, because females often dedicate more resources to offspring production, which may lead to plastic investment in colour signals and plastic sexual dichromatism. Oestradiol is a candidate mediator of this trade-off because it regulates reproductive physiology and may also influence the expression of coloration. We tested this hypothesis by giving female common waxbills (Estrilda astrild) either oestradiol (17β-oestradiol) or empty implants during the early breeding season and measured spectral reflectance of carotenoid-based bill coloration weekly for two months. Using a model of avian vision, we found that bill colour in oestradiol-implanted females became less saturated, less red in hue and brighter, compared with control females and with unimplanted males. This resulted in a change in bill sexual dichromatism from imperceptible to perceptible. Results support the hypothesis that female reproductive physiology influences investment in coloration through changes in oestradiol and show a form of female-driven plastic sexual dichromatism. Greater sensitivity of female colour to physiological and/or environmental conditions helps explain why differences in sexual dichromatism among species differing in ecology often evolve owing to changes in female rather than male phenotype.

Evaluating different metrics to study small color differences: the red bill and plumage of common waxbills as a case study

Evaluating different metrics to study small color differences: the red bill and plumage of common waxbills as a case study

Cloaca‐ and feather‐associated bacteria communities in common waxbills Estrilda astrild

Host‐associated microbial communities are essential for host homeostasis and health. Most research on microbiotas is restricted to model host species and, since microbe–host dynamics can be species‐specific, we still lack a good taxonomic, ecological and evolutionary understanding of microbiotas in wild hosts, including birds. Given the diversity of avian host species, their habitat specializations, ecological requirements and life‐history traits, we need to characterize the dynamics of microbiotas from taxonomically diverse bird species. Here we describe cloaca and feather microbiotas of a population of common waxbills Estrilda astrild living in a large open‐air mesocosm, and compare it to microbiotas sampled one year later for a subset of this population, and to the microbiotas of free‐ranging waxbills from the same region. We found clear differences between microbiota from the cloaca, which contained some taxa that may be found in seeds, and from feathers, which contained some taxa that have been previously found in plants and soil. We found limited evidence for sexual differences in both cloaca and feather microbiotas, likely due to the gregariousness, similar behaviour and habitat use of both male and female waxbills. Microbial diversities of waxbills from the mesocosm were representative of those found in free‐ranging individuals. Also, structural differences between microbiota from mesocosm and free‐ranging waxbills seemed to be small and comparable to differences found in microbiota from the mesocosm in consecutive years. These results indicate that this mesocosm population could be used as a model in future studies investigating microbiota–host dynamics.

Collective foraging: Experimentally increased competition decreases group performance exploiting a permanent resource

Abstract Foraging collectively offers advantages, such as access to social information on food locations, but it may also intensify competition for local resources. Social information may be most advantageous during ecologically challenging conditions, when food sources are scarce or unpredictable, which predicts more collective foraging during such conditions. Alternatively, higher within‐group competition when resources are scarce might destabilize social groups and reduce collective foraging. To evaluate these effects, we experimentally decreased the number and predictability of food sources (feeders with ad libitum seeds) available to wild‐caught common waxbills Estrilda astrild living in a large open‐air mesocosm. Compared to control periods, in the treatment with few food sources competitive aggressiveness at feeders increased, the social network became more fragmented, with on average weaker associations between individuals, and foraging groups became smaller. Foraging groups also spent less time per visit to the feeding area, individuals spent less time at the feeders per group visit and had to make more visits to the feeding area per day, all of which indicate less efficient exploitation of the food sources. These effects were also observed when the number of feeders changed unpredictably across days. Even though the collective behaviour of waxbills appeared to exacerbate, rather than mitigate, the ecological challenges of reduced or unpredictable food sources, we suggest that, in nature, this increased aggressiveness and fragmentation of the social network may function adaptively as an early trigger to explore alternative foraging locations before local food sources are severely depleted. Read the free Plain Language Summary for this article on the Journal blog.

A test of context- and sex-dependent dopaminergic effects on the behavior of a gregarious bird, the common waxbill, Estrilda astrild.

The dopaminergic (DAergic) system has well-known influences on behavioral and cognitive functions. Previous work with common waxbills (Estrilda astrild) reported context-specific DAergic effects that could have been due to social environment. Manipulating the dopamine D2-like receptor family (D2R) pathways had opposing effects on behavior depending on whether waxbills were tested alone or in a small cage with a mirror as a social stimulus. As waxbills are highly gregarious, it was hypothesized that being alone or perceiving that they have a companion might explain this context dependence. To test context-dependent DAergic effects, we compared behavioral effects of D2R manipulation in waxbills in the same familiar environment, but either alone or with a familiar, same-sex companion. We found that D2R agonism decreased movement and feeding, similar to previous results when testing waxbills alone. However, contrary to the hypothesis of dependence on social context, we found that the behavioral effects of the D2R agonist were unchanged when waxbills were tested with a companion. The context dependence reported earlier might thus be due to other factors, such as the stress of being in a novel environment (small cage) or with an unfamiliar social stimulus (mirror image). In tests with a companion, we also found a sex-specific social effect of D2R manipulation: D2R blocking tended to decrease aggression in males but to increase it in females. Together with past work, our results suggest that DAergic effects on behavior involve different types of context or sex dependence.