Biology subjects

Doutrelant, C.

Publications and source records attributed to Doutrelant, C..

17 recordsLinked to original sources

bioRxiv2026

No evidence of sentinel behaviour in a highly social bird based on an artificial set-up

Sentinel behaviour occurs when individuals use raised positions to scan for predators while the rest of the group forages. Here, we investigated whether a colonial cooperatively breeding species that forages in large groups, the sociable weaver, Philetairus socius, displays sentinel behaviour. This behaviour has been reported in species with similar ecology, behaviour and foraging habits, (e.g. ground foraging in open habitats where aerial predators are common) and, hence, we expected that it could occur in sociable weavers. On the other hand, sentinel behaviour appears to be less common in species that live in very large groups. We used an experimental set-up consisting of an artificial feeding station and perches to assess occurrence of sentinel related behaviours: (i) perching events > 30s on an elevated position, (ii) head-movements and (iii) alarm calling. Birds were seldom observed perching while others fed, and those that did, perched for periods that were too short to be considered as sentinel behaviour (less than 5s on average). Our results suggest that this behaviour is uncommon or even absent in sociable weavers. We discuss whether other factors such as foraging in very large groups, or interspecific foraging associations might make sentinel behaviour less important in this species.

animal behavior and cognition↗

bioRxiv2026

Predation and the Evolution of Island Bird Plumage Colouration: Experimental Insights from Island and Mainland Environments

Islands serve as natural laboratories for exploring evolutionary processes, often fostering unique species through their isolation and distinct ecological conditions. These environments present opportunities to study how a range of selective pressures shape biodiversity. Bird plumage colouration is one trait that has shown to consistently change in island populations, and predation has been hypothesized to influence these differences. While animals often face a trade-off between signalling to conspecifics and avoiding detection by predators, the role of predation in shaping conspicuousness remains underexplored experimentally. In this study, we asked how predation pressure differs between insular and mainland habitats, and whether predation risk covaries with conspicuousness of male and female birds across environments. In a field experiment, we investigated predation rates using 3D-printed models painted to represent both sexes of 12 bird species from three archipelagos (Madeira, Azores, and Canary Islands) and their closest mainland relatives. These models were deployed in the species natural environments to measure hit rates (a proxy for predation risk), accounting for factors that influence prey detectability, such as colour of the models, background contrast, and vegetation. We found that models on the islands experienced less hits compared to those on the mainland, while sexual dichromatic models were more likely to be dislodged on the mainland. In addition, for mainland sites, increased chromatic contrast correlated with a higher probability of dislodgment, suggesting that more conspicuous models were more likely to be hit. These results highlight that while predation constrains conspicuousness, other ecological and evolutionary factors likely drive the reduced plumage colouration observed in island birds. Our research offers experimental insights into how predation interacts with conspicuous traits in shaping plumage colouration in birds.

evolutionary biology↗

bioRxiv2026

Sex-specific Flexibility in Breeding and Helping Strategies in the Sociable Weaver (Philetairus socius)

Helping-at-the-nest is often viewed as a precursor to reproduction, but switching between breeder and helper roles has been documented in some species. Such flexibility should depend on the opportunities and benefits of helping, which could differ between sexes due to dispersal strategies and social structure. However, whether breeding-helping flexibility is widespread and sex-specific remains unknown. Here, we investigated sex-specific strategies in breeding-helping flexibility using a 10-year dataset (1955 individuals) on sociable weavers (Philetairus socius), a colonial cooperative breeder in which males are typically philopatric whereas females disperse. Both sexes helped for several years, with males helping more frequently than females and for twice as long (0-13 vs 0-10 years). Around 40% of non-dispersing birds never became breeders and 50% of individuals bred without helping first. Both sexes switched roles between- and within-seasons but males were more likely to alternate (respectively four and six times more than females and up 15 switches across seven years). Our study reveals important flexibility and sex differences in breeder-helper roles, consistent with sex-biased dispersal, spatial breeding proximity and possible indirect fitness benefits. These factors could play a role promoting the evolution of helping across life-stages, not only pre-reproduction, but also reproductive and post-reproductive individuals.

evolutionary biology↗

bioRxiv2025

Experimentally assessing the role of foraging encounters on social partner choice in a kin-biased bird society

Kin-based social environments are often characterized by prolonged parent-offspring associations and limited dispersal in at least one sex, leading to groups composed of kin as social partners. These high rates of social interactions among relatives in cooperative societies make it difficult to distinguish whether social partner choice is driven by kinship or by repeated encounters with individuals situated at proximity. Here, we experimentally increased the number of foraging encounters among non-kin at a custom feeder setup in the sociable weaver (Philetairus socius), a colonial, cooperatively breeding bird with a kin-based social structure. Individuals encouraged to forage more frequently with non-relatives subsequently developed stronger foraging associations with non-kin at separate, unrestricted feeders. These findings show that repeated opportunities for interaction can promote non-kin social associations even within a kin-based society, contributing to the understanding of proximate mechanisms that underlie social structure.

animal behavior and cognition↗

bioRxiv2025

Infanticide in a colonial cooperative bird is not associated with direct reproductive benefits

Infanticide, the killing of dependent young by adult conspecifics, is an extreme form of conflict that remains poorly understood. Previous studies suggest that it is associated with reproductive benefits, either by making breeders newly available for reproduction or by increasing offspring care and reducing competition for resources. In addition, infanticide may result from a reproductive trade-off, where parents kill their offspring if environmental conditions compromise their reproductive value. Here, we combine video, genetic and individual-level reproductive data collected over 12 years to describe infanticide in a highly social, cooperative bird, the sociable weaver Philetairus socius and to establish whether direct reproductive benefits or life-history trade-offs are possible motivators for this behaviour. We documented 50 cases of infanticide and identified 27 aggressors with known histories. These were mostly born outside the colonies where they committed infanticide (63%) and there was a bias towards younger individuals. Aggressors were usually not part of the victims breeding group (74%), but in two cases infanticide was committed by the breeding female, and in five by helpers. In most cases, aggressors were not reproducing at the time of the infanticide, were not recorded mating with any of the breeders or helpers from the attacked nest, nor occupied the nest from where the chicks were evicted. Only 13 of the known aggressors were confirmed as breeders after the attacks, and these mostly reproduced at the colony where the attacks were committed. Overall, we found no evidence for direct reproductive benefits of infanticide in sociable weavers. However, the younger age of aggressors, lack of genetic relatedness to the victims and future breeding at the colony suggest that competition between breeding groups, and hence indirect reproductive benefits, could provide motivation for infanticide in this population. Additional work over longer periods is needed to identify these possible indirect fitness benefits of infanticide.

animal behavior and cognition↗

bioRxiv2025

Disentangling urbanisation, climate effects and their interaction on ornamental colourations

Urbanisation and climate change can both affect phenotype expression across taxa. Most evidence collected so far has focused on exploring these two phenomena on isolation. Currently, the combined effects of climate change and urbanisation remain underexplored, despite being among the greatest challenges faced by biodiversity. Here, we use a decade-long, individual-based study of urban and forest great tits (Parus major) to analyse urbanisation, climate and their interactive effects on yellow breast colouration, a carotenoid-based trait. We find that urban birds exhibit duller colourations than forest counterparts, being 10-20% less chromatic, with first-year birds and males being more negatively impacted by cities. Additionally, birds in the city are more sexually dichromatic than in the forest. Over the decade, colouration differences between habitats remain stable, following a similar quadratic temporal pattern. Finally, while climate has a weak effect on colouration, urban birds appear more sensitive to its influence than forest birds. Our results indicate urbanisation has a stronger impact than last decade climatic variation on great tit colouration, though both factors may interact. The heightened sensitivity of first-year birds and increased sexual dichromatism in cities may alter the strength of natural and sexual selection on this trait in urban environments.

ecology↗

bioRxiv2025

Long-term evaluation of the association between dominance, bib size, sex and age

The association between dominance and phenotypic traits ( badges of status) has been recently questioned, since it has been found to show more variation across populations and time than expected. Using an eleven-year dataset, encompassing more than 1,800 individuals, we studied the association between the size of a melanin-based plumage trait (a black patch under the beak or bib), individual attributes (age and sex) and dominance. Our study model, the sociable weaver (Philetairus socius), is a small passerine, which lives year-round in colonies of varying size. Bib sizes were obtained from pictures and automatically pre-processed with an object segmentation deep learning network. We recorded 36,346 dominance-related interactions to estimate dominance hierarchies. We then investigated the effect of sex and age on bib size, and the overall and between-year association of bib size and age with dominance for each sex. We found that bib size increased with age within individuals of both sexes. Age was a strong and consistent predictor of dominance in males, but not in females. Nevertheless, dominance was not correlated with bib size in males and in females. Finally, these relationships did not strongly vary between years. Our results suggest that males and females may use different factors to regulate dominance interactions. Furthermore, our longitudinal dataset allowed us to show that bib size is not a badge of status in our population even though its growth encodes information on age. These results highlight the importance of considering multiple traits over time when studying morphological signalling of dominance hierarchy.

animal behavior and cognition↗

bioRxiv2024

Foraging associations are related with helping interactions in a cooperatively breeding bird

Kin selection has been the main hypothesis explaining helping behaviour in cooperative breeders, with evidence being largely based on the observation that helpers tend to provide to related offspring. However, kin-biased help could conceal additional, mechanisms contributing to the maintenance of cooperation. Under pay-to-stay, group augmentation and partner choice hypotheses, a range of direct benefits can arise through helping. Here, we explored this potential mechanism by testing whether the social associations of breeding individuals were related with the help that they received from non-breeding individuals. We collected social associations from PIT-tagged sociable weavers, Philetairus socius, at RFID feeding stations, which allowed us to compare associations between breeders and either their helpers (mostly kin) or their other kin that did not help--before, during and after reproduction. Using correlative tests and data-driven simulations, we show that helpers have stronger foraging bonds with breeders than non-helping kin, and that these stronger bonds are present both prior and post breeding. Furthermore, helper-breeding female social affiliations were positively correlated with the amount of help provided. Our results suggest that direct benefits of social associations complement kin selection to determine helping decision, and that these in turn influence future social associations.

animal behavior and cognition↗

bioRxiv2024

From raw footage to behaviour: an automated pipeline for activity monitoring and behaviour identification in the wild

O_LIStudies of animal behaviour usually rely on direct observations or manual annotations of video recordings. However, such methods can be very time-consuming and error-prone, leading to sub-optimal sample sizes. Recent advances in deep-learning show great potential to overcome such limitations, nevertheless, most currently available behavioural recognition solutions remain focused on captivity settings. C_LIO_LIHere, we present a deployment-focused framework to guide researchers in building behavioural recognition systems from video data, using Long Short-Term Memory (LSTM) networks to classify behavioural sequences across consecutive frames. C_LIO_LILSTMs allowed to: 1) monitor nest activity by detecting the birds presence and simultaneously classifying the type of trajectory: i.e., nest-chamber entrance or exit; and 2) identify the behaviour performed: building, aggression or sanitation. Using our framework, we outperformed human annotators when jointly considering error and speed. Model performance improved with challenging training instances, and remained robust even with modest sample sizes. LSTM also outperformed YOLO ("You Only Look Once"), highlighting the critical role of temporal sequence information in behavioural analysis. C_LIO_LIWe demonstrate that our approach is replicable across three bird species and applicable to deployment videos, highlighting its value as a generalizable and transferable tool for long-term studies in the wild. C_LI DATA AVAILABILITYScripts, models, and data required to reproduce this work are available on Zenodo (DOIs: 10.5281/zenodo.18681623 and 10.5281/zenodo.18695178).

animal behavior and cognition↗

bioRxiv2024

A deep learning approach to detect and visualise sexual dimorphism in monomorphic species

Sex recognition is facilitated by dimorphism in some traits. However, humans often fail to find the traits that allow to distinguish between sexes in other species. Deep learning has the potential to surpass humans in identifying cryptic differences between sexes, but, so far, has rarely been used to assess sexual dimorphism. In this study, we evaluated (i) the ability of a fine-tuned classification neural network, EfficientNet, to find differences between sexes in a species that appears monomorphic to humans, the sociable weaver (Philetairus socius). We then assessed (ii) the benefits of Grad-CAM visualisation techniques to understand which parts of the individuals are used by the network to differentiate the sexes. We trained 10-folds cross-validation models on more than 4,500 pictures of the head from more than 1,300 individuals. Our results show that the network can predict sex of sociable weavers with an accuracy of 76%, which is considerably higher than humans performance, and that the model was similarly good at predicting females and males. When interpreting the probability of being classified to one sex, our results further reveal an effect of the interaction of sex with age on the confidence score of the models which shows that younger males are less masculine than older ones, and older females more masculine than younger ones. Finally, using Grad-CAM we found that the model mostly uses the beak region to predict the sex of individuals. Overall, this work shows that artificial intelligence has the potential to be a non-invasive sexing tool, surpassing human capabilities and aiding in pinpointing potential cryptic dimorphic body parts that have yet to be identified. In birds, half of the worlds species appear sexually monomorphic to humans, and re-evaluation of species dimorphism with this type of methods could deepen our understanding of the effect of selection on animal traits.

zoology↗

bioRxiv2024

Advancing cooperative breeding research with a peer-reviewed and "live" Cooperative-Breeding Database (Co-BreeD)

Research on cooperative breeding (a system with the core characteristic of individuals providing care for the offspring of others) is important for understanding sociality and cooperation. However, large-scale comparative analyses on the drivers and consequences of cooperation frequently use considerably inaccurate datasets (e.g. due to inconsistent definitions and outdated information). To advance comparative research on cooperative breeding, we introduce the Cooperative-Breeding Database (Co-BreeD), a growing database of key socio-biological parameters of birds and mammals. First, we describe Co-BreeDs structure as a (i) sample-based (i.e. multiple samples per species linked to an exact sampling location and period), (ii) peer-reviewed and (iii) updatable resource. Respectively, these curating principles allow for (i) investigating intra- and inter-species variation and linking between fine-scale social and environmental parameters, (ii) accuracy and (iii) continuous correction and expansion with the publication of new data. Second, we present the first Co-BreeD dataset, which estimates the prevalence of breeding events with potential alloparents in 265 samples from 233 populations of 150 species, including 2 human societies (N = 26,366 breeding events). We conclude by demonstrating (i) how Co-BreeD facilitates more accurate comparative research (e.g. increased explanatory power by enabling the study of cooperative breeding as a continuous trait, and statistically accounting for the sampling error probabilities), and (ii) that cooperative breeding in birds and mammals is more prevalent than currently estimated.

animal behavior and cognition↗

bioRxiv2021

Reduction in population size and not a shift in parasite community affect evolution of immune genes in island birds.

AO_SCPLOWBSTRACTC_SCPLOWShared ecological conditions encountered by species that colonize islands often lead to the evolution of convergent phenotypes, commonly referred to as "island syndrome". Reduced immune functions have been previously proposed to be part of this syndrome, as a consequence of the reduced diversity of pathogens on island ecosystems. According to this hypothesis, immune genes are expected to exhibit genomic signatures of relaxed selection pressure in island species. In this study, we used comparative genomic methods to study immune genes in island species (N = 20) and their mainland relatives (N = 14). We gathered public data as well as generated new data on innate (TLR: Toll-Like Receptors, BD: Beta Defensins) and acquired immune genes (MHC: Major Histocompatibility Complex classes I and II), but also on hundreds of genes with various immune functions. As a control, we used a set of 97 genes, not known to be involved in immune functions based on the literature, to account for the increased drift effects of the lower effective population sizes in island species. We used synonymous and non-synonymous variants to estimate the selection pressure acting on immune genes. We found that BDs and TLRs have higher ratios of non-synonymous over synonymous polymorphisms (Pn/Ps) than randomly selected control genes, suggesting that they evolve under a different selection regime. However, simulations show that this is unlikely to be explained by ongoing positive selection or balancing selection. For the MHC genes, which evolve under balancing selection, we used simulations to estimate the impact of population size variation. We found a significant effect of drift on immune genes of island species leading to a reduction in genetic diversity and efficacy of selection. However, the intensity of relaxed selection was not significantly different from control genes, except for MHC class II genes. These genes exhibit a significantly higher level of non-synonymous loss of polymorphism than expected assuming only drift and evolution under frequency dependent selection, possibly due to a reduction of extracellular parasite communities on islands. Overall, our results showed that demographic effects lead to a decrease in the immune functions of island species, but the relaxed selection that is expected to be caused by a reduced parasite pressure may only occur in some categories of immune genes.

evolutionary biology↗

bioRxiv2021

Identifying drivers of spatio-temporal variation in survival in four blue tit populations

In a context of rapid climate change, the influence of large-scale and local climate on population demography is increasingly scrutinized, yet studies are usually focused on one population. Demographic parameters, including survival, can vary significantly across populations of a given species, depending on global or local climatic fluctuations but also on many other population-specific parameters such as breeding density, habitat naturalness, predation or parasitism. Such ecological differences between populations could lead to different paces-of-life (POL), whereby populations where individuals display higher reproductive investment and bolder behaviours would have lower survival probabilities. We use here long-term (19 to 38 years) monitoring datasets from four Mediterranean populations of blue tits (Cyanistes caeruleus) to investigate the effects of sex, age class, large-scale and local climate temporal variation and population breeding density, on adult survival, using Capture-Mark-Recapture modelling. Environment heterogeneity in these four populations (two in evergreen and two in deciduous forests) has been linked to strong multi-trait phenotypic variation, suggesting blue tits in deciduous forests display faster POL compared to their conspecifics in evergreen habitats. The present results show heterogeneity in average survival probabilities across the four populations, with, as predicted, lower survival in the fast blue tits occupying deciduous habitats. Interestingly, the year-to-year variation in survival probabilities was synchronous among populations. This suggests that regional environmental conditions could drive survival fluctuations across populations. However, breeding densities were not correlated across populations, and we found no evidence that adult survival is correlated with either large-scale or local, climate temporal variation in these four blue tit populations. Finally, two of the focal populations displayed a linear temporal decrease in adult survival over the study period, calling for further investigation to explain this decline. Overall, this multi-site study shows that blue tit parental survival from one spring to the next can vary substantially across years, in a synchronous way across populations, yet the climate indices we used are not correlated with the temporal variation. This calls for further investigations in other potential drivers such as resource (in particular insect) abundance, predation or parasitism.

ecology↗

bioRxiv2019

Deep learning-based methods for individual recognition in small birds

O_LIIndividual identification is a crucial step to answer many questions in evolutionary biology and is mostly performed by marking animals with tags. Such methods are well established but often make data collection and analyses time consuming and consequently are not suited for collecting very large datasets. C_LIO_LIRecent technological and analytical advances, such as deep learning, can help overcome these limitations by automatizing data collection and analysis. Currently one of the bottlenecks preventing the application of deep learning for individual identification is the need of hundreds to thousands of labelled pictures required for training convolutional neural networks (CNNs). C_LIO_LIHere, we describe procedures that improve data collection and allow individual identification in captive and wild birds and we apply it to three small bird species, the sociable weaver Philetairus socius, the great tit Parus major and the zebra finch Taeniopygia guttata. C_LIO_LIFirst, we present an automated method that allows the collection of large samples of individually labelled images. Second, we describe how to train a CNN to identify individuals. Third, we illustrate the general applicability of CNN for individual identification in animal studies by showing that the trained CNN can predict the identity of birds from images collected in contexts that differ from the ones originally used to train the CNNs. Fourth, we present a potential solution to solve the issues of new incoming individuals. C_LIO_LIOverall our work demonstrates the feasibility of applying state-of-the-art deep learning tools for individual identification of birds, both in the lab and in the wild. These techniques are made possible by our approaches that allow efficient collection of training data. The ability to conduct individual identification of birds without requiring external markers that can be visually identified by human observers represents a major advance over current methods. C_LI

ecology↗

bioRxiv2019

How to make methodological decisions when inferring social networks

Constructing and analysing social networks data can be challenging. When designing new studies, researchers are confronted with having to make decisions about how data are collected and networks are constructed, and the answers are not always straightforward. The current lack of guidance on building a social network for a new study system might lead researchers to try several different methods, and risk generating false results arising from multiple hypotheses testing. We suggest an approach for making decisions when developing a network without jeopardising the validity of future hypothesis tests. We argue that choosing the best edge definition for a network can be made using a priori knowledge of the species, and testing hypotheses that are known and independent from those that the network will ultimately be used to evaluate. We illustrate this approach by conducting a pilot study with the aim of identifying how to construct a social network for colonies of cooperatively breeding sociable weavers. We first identified two ways of collecting data using different numbers of feeders and three ways to define associations among birds. We then identified which combination of data collection and association definition maximised (i) the assortment of individuals into breeding groups (birds that contribute towards the same nest and maintain cohesion when foraging), and (ii) socially differentiated relationships (more strong and weak relationships than expected by chance). Our approach highlights how existing knowledge about a system can be used to help navigate the myriad of methodological decisions about data collection and network inference.\n\nSIGNIFICANCE STATEMENTGeneral guidance on how to analyse social networks has been provided in recent papers. However less attention has been given to system-specific methodological decisions when designing new studies, specifically on how data are collected, and how edge weights are defined from the collected data. This lack of guidance can lead researchers into being less critical about their study design and making arbitrary decisions or trying several different methods driven by a given preferred hypothesis of interest without realising the consequences of such approaches. Here we show that pilot studies combined with a priori knowledge of the study species social behaviour can greatly facilitate making methodological decisions. Furthermore, we empirically show that different decisions, even if data are collected under the same context (e.g. foraging), can affect the quality of a network.

animal behavior and cognition↗

bioRxiv2019

Hummingbird iridescence: an unsuspected structural diversity influences colouration at multiple scales

AbstractIridescent colours are colours that change depending on the angle of illumination or observation. They are produced when light is reflected by multilayer structures or diffracted by gratings. While this phenomenon is well understood for simple optical systems, it remains unclear how complex biological structures interact with light to produce iridescence. There are very few comparative studies at interspecific level (often focusing on a single colour patch for each species), resulting in an underestimation of structure diversity. Using an interdisciplinary approach combining physics and biology, we here quantify the colour and structure of 36 hummingbirds species evenly distributed across the phylogeny. We explore at least 2 patches per species, which are assumed to be under different selective regimes. For each patch, we measure structural features (number of layers, layer width, irregularity, spacing, etc.) of the feathers at different scales using both optical and electronic microscopy and we measure colour using a novel approach we developed to encompass the full complexity of iridescence, including its angular dependency. We discover an unsuspected diversity of structures producing iridescence in hummingbirds. We also study the effect of several structural features on the colour of the resulting signal, using both an empirical and modelling approach. Our findings demonstrate the need to take into account multiple patches per species and suggest possible evolutionary pressures causing the evolutionary transitions from one melanosome type to another.

evolutionary biology↗

bioRxiv2019

Distribution of iridescent colours in hummingbird communities results from the interplay between selection for camouflage and communication

Identification errors between closely related, co-occurring, species may lead to misdirected social interactions such as costly interbreeding or misdirected aggression. This selects for divergence in traits involved in species identification among co-occurring species, resulting from character displacement. On the other hand, predation may select for crypsis, potentially leading co-occurring species that share the same environment and predators to have a similar appearance. However, few studies have explored how these antagonistic processes influence colour at the community level. Here, we assess colour clustering and overdispersion in 189 hummingbird communities, tallying 112 species, across Ecuador and suggest possible evolutionary mechanisms at stake by controlling for species phylogenetic relatedness. In hummingbirds, most colours are iridescent structural colours, defined as colours that change with the illumination or observation angle. Because small variations in the underlying structures can have dramatic effects on the resulting colours and because iridescent structures can produce virtually any hue and brightness, we expect iridescent colours to respond finely to selective pressures. Moreover, we predict that hue angular dependence - a specific aspect of iridescent colours - may be used as an additional channel for species recognition. In our hummingbird assemblages in Ecuador, we find support for colour overdispersion in ventral and facial patches at the community level even after controlling for the phylogeny, especially on iridescence-related traits, suggesting character displacement among co-occurring species. We also find colour clustering at the community level on dorsal patches, suspected to be involved in camouflage, suggesting that the same cryptic colours are selected among co-occurring species. This article has been peer-reviewed and recommended by Peer Community In Evolutionary Biology

ecology↗