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Dakin, R.

Publications and source records attributed to Dakin, R..

At least 19 recordsLinked to original sources
bioRxiv2026

Peak performance is repeatable and captures large individual differences in ruby-throated hummingbirds

Locomotor performance often determines the outcome of interactions with competitors, predators, and prey. In flying animals, the asymptotic load-lifting assay measures maximal muscle power output in vertical flight. Previous studies of small birds have shown that load-lifting performance is linked to flight maneuverability and the outcome of competitive species interactions. Here, we quantify sources of performance variation within a species, namely repeatability, and determine the number of trials that accurately capture individual differences. We conducted 124 load-lifting trials on 13 wild-caught male ruby-throated hummingbirds (Archilochus colubris), testing each individual repeatedly over a 3-day period. We report large individual differences in peak performance, with 70% of the total variation in lifted mass attributed to differences among males. Notably, these differences in muscle performance are independent of body mass and size. An additional 23% of the variation in lifted mass was due to short-term fluctuations, wherein a given males performance varied across trials and days. We find no systematic effects of experience or time on load-lifting performance. Using simulation, we test the effect of different sampling protocols for measuring individual performance, and show that single-trial protocols yield the highest repeatabilities, but are less suitable for capturing the true underlying differences among individuals. We discuss recommendations for future studies that aim to measure maximum performance. Overall, our results show that the asymptotic load-lifting assay reveals large individual differences and can closely reflect individuals true maximum capacity. Summary statementMale ruby-throated hummingbirds exhibit large, consistent differences in load-lifting performance, highlighting peak flight performance as a potential driver of differences in competitive abilities between conspecifics.

zoology↗
bioRxiv2026

A look inside the net: freshwater turtles assort with conspecifics in feeding aggregations

Non-avian reptiles have been assumed to be non-social for many years, yet recent studies show diverse social behaviours in squamates, crocodilians, and turtles. Here, we investigate social structure within feeding aggregations of three freshwater turtle species caught in baited traps in a coastal marsh over 12 years. In 488 instances in which traps contained turtles, 45% contained multiple individuals, and these aggregations were strongly positively assorted by species. midland painted turtles (Chrysemys picta) and Blandings turtles (Emydoidea blandingii) were captured with conspecifics more often than expected in a non-social null model. Snapping turtles (Chelydra serpentina), the largest species in this study, were caught with conspecifics at rates consistent with the non-social null model, and were avoided by heterospecifics. This suggests that species differences play a role in how feeding aggregations are structured, with painted and Blandings turtles driving positive species assortment while avoiding snapping turtles around food sources. We did not detect significant intraspecific sex assortment in any of the three species, nor did turtle body size strongly affect the probability of aggregating with conspecifics at the perceived food source in the traps. Our study illustrates how long-term monitoring data can be used to investigate social structure in wild populations, an approach that may be valuable for species of conservation concern. Significance StatementReptile sociality has been historically overlooked, but recent work has revealed intriguing social behaviours in non-avian reptiles. We investigated associations among three species of freshwater turtle, captured in baited traps over 12 years of trapping. Turtles in these feeding aggregations grouped with their own species more often than expected by chance. This result was driven by the two smaller-bodied species (midland painted turtle and Blandings turtle), which were more likely to be caught with conspecifics than with other species. In contrast, the largest species (snapping turtle) showed no evidence of attraction to other snapping turtles, and midland painted turtles and Blandings turtles showed avoidance of the larger snapping turtles. Our analyses illustrate how long-term monitoring data can be used to uncover previously unrecognized social behaviour in turtles and other species in which behaviour is difficult to observe directly.

animal behavior and cognition↗
bioRxiv2025

Foraging behavior and ecology drive the evolution of humeral shape in hummingbirds

Understanding how locomotion-related skeletal elements evolve under biomechanical and ecological constraints is central to animal evolutionary biology. In hummingbirds (Trochilidae), the humerus plays a key role in force transmission during hovering and flapping flight, yet the drivers of its shape evolution have not been examined. We combined geometric morphometrics with phylogenetic comparative analyses to examine humeral shape variation, evolutionary rates, and phenotypic integration in male hummingbirds from 78 species. Our analyses identified humerus allometry as the dominant predictor of shape, revealing a pattern in which larger humeri show broader proximal epiphyses, increased shaft robustness, and reduced curvature. In addition to this scaling pattern, we find that male humerus shape differs subtly among hummingbird species that differ in the use of aggression during nectar foraging. Evolutionary rates of humeral shape were heterogeneous and decoupled from ecological predictors. We also find phenotypic integration between the proximal and distal regions of the humerus, indicating coordinated evolution. Together, these results show that humeral evolution in hummingbirds is governed primarily by biomechanical scaling and internal integration, with foraging ecology introducing secondary, size-dependent modifications. This work highlights the importance of considering scaling and internal integration when interpreting morphological evolution in locomotor systems across vertebrates.

evolutionary biology↗
bioRxiv2023

Learning when to learn: hummingbirds adjust their exploration behaviour to match the value of information

Exploration is a key part of an animals ability to learn. The exploration-exploitation dilemma predicts that individuals should adjust their exploration behaviour according to changes in the value of information. Here, we test this prediction by tracking ruby-throated hummingbirds as they foraged repeatedly from a large array of artificial flowers, wherein 25% of the flowers contained a sucrose reward. Similar to real-world floral dynamics, the reward locations were consistent in the short-term, but varied from day to day. Thus, the value of information about the flower contents would be greatest at the beginning of a daily foraging session, and decay toward the end of each session. We tracked five individual hummingbirds in repeated foraging sessions, comprising more than 3,400 floral probes. We analyzed two metrics of their exploration behaviour: (1) the probability that a bird would shift from probing one flower to another, and (2) the Shannon information entropy of a sequence of flowers probed. We show that initially, the hummingbirds increased their exploration behaviour as time elapsed within a session. As they performed more sessions and learned the rules of the environment, the hummingbirds switched to explore more diverse choices at the beginning of a foraging session, when the value of information was high, and less diverse choices toward the end of a session. Our results suggest that foraging hummingbirds can learn when to learn, highlighting the importance of plasticity in exploration behaviour. HighlightsO_LIExploration is a necessary part of learning C_LIO_LIForagers must balance sampling for information with the use of known rewards C_LIO_LIHummingbirds learned to explore more when the value of new information was high C_LIO_LIApparent mistakes may actually represent an information-seeking strategy C_LI

animal behavior and cognition↗
bioRxiv2023

How prior and p-value heuristics are used when interpreting data

Scientific conclusions are based on the ways that researchers interpret data, a process that is shaped by psychological and cultural factors. When researchers use shortcuts known as heuristics to interpret data, it can sometimes lead to errors. To test the use of heuristics, we surveyed 623 researchers in biology and asked them to interpret scatterplots that showed ambiguous relationships, altering only the labels on the graphs. Our manipulations tested the use of two heuristics based on major statistical frameworks: (1) the strong prior heuristic, where a relationship is viewed as stronger if it is expected a priori, following Bayesian statistics, and (2) the p-value heuristic, where a relationship is viewed as stronger if it is associated with a small p-value, following null hypothesis statistical testing. Our results show that both the strong prior and p-value heuristics are common. Surprisingly, the strong prior heuristic was more prevalent among inexperienced researchers, whereas its effect was diminished among the most experienced biologists in our survey. By contrast, we find that p-values cause researchers at all levels to report that an ambiguous graph shows a strong result. Together, these results suggest that experience in the sciences may diminish a researchers Bayesian intuitions, while reinforcing the use of p-values as a shortcut for effect size. Reform to data science training in STEM could help reduce researchers reliance on error-prone heuristics. Significance StatementScientific researchers must interpret data and statistical tests to draw conclusions. When researchers use shortcuts known as heuristics, it can sometimes lead to errors. To test how this occurs, we asked biologists to interpret graphs that showed an ambiguous relationship between two variables, and report whether the relationship was strong, weak, or absent. We altered features of the graph to test whether prior expectations or a statistic called the p-value could influence their interpretations. Our results indicate that both prior expectations and p-values can increase the probability that researchers will report that ambiguous data shows a strong result. These findings suggest that current training and research practices promote the use of error-prone shortcuts in decision-making.

scientific communication and education↗
bioRxiv2023

Social network structure scales with group size in a multi-species analysis

Social networks can shape the evolution and transmission of behaviours. Recent studies have characterized social networks within species, but we know relatively little about the drivers of variation in the structure of social networks across species. Here, we analyze a database of 631 social networks from more than 30 animal species to test how social network properties scale with group size. We examine three properties of social network topology: the uniformity of edge weights within the group, the selectivity of individuals for particular social partners, and the amount of heterogeneity among individuals in social behaviour. We show that most of the variation in these three network properties is due to differences between focal species and/or study methodologies, with only negligible differences between the three animal classes in our analysis (birds, mammals, and insects). Our analysis also indicates that group size is the key factor that determines the topology of animal social networks. In smaller groups, edge weights are distributed more uniformly, and individuals show greater selectivity regarding their social partners. These results suggest that there are general scaling rules governing the social networks of diverse animal species. In small groups, individuals form strong connections to a selective set of partners, whereas in large groups, weaker ties are common, and individuals are less likely to limit their interactions to specific partners. Significance StatementSociality is observed throughout the animal kingdom. Animal societies also vary widely in group size, from a few individuals to groups with millions on individuals. How do animal social networks vary across this spectrum? We investigated this question using data compiled from recent bird, mammal, and insect studies. Surprisingly, we found broad overlap in the social network structures of these three distinct animal classes. We tested the effect of group size on social network structure, and found that in small groups, individuals form stronger social ties with preferred social partners; by contrast, animals in large groups have weaker and less selective social ties. These results suggest that diverse animal groups are governed by similar processes that determine the structure of their social networks.

animal behavior and cognition↗
bioRxiv2023

Social flocking increases in harsh and challenging environments

Grouping with others can provide enhanced information about resources and threats. A key hypothesis in social evolution proposes that individuals can benefit from social information in environments where it is challenging to meet energetic needs. Here, we test this hypothesis by examining the environmental drivers of conspecific flocking behaviour in a large archive of citizen science observations of two common North American birds, the dark-eyed junco (Junco hyemalis) and black-capped chickadee (Poecile atricapillus). To quantify flocking behaviour, we apply the index of dispersion, D, as a metric of clumpiness in each species spatiotemporal distribution. We show that juncos in winter are nearly always more clustered than a random expectation, whereas chickadees span a range from uniform to socially clustered distributions. In both species, the degree of social clustering strongly increases with abundance. We identify several key environmental variables that explain the extent of conspecific flocking in both species. Flocks are more socially clustered at higher latitudes, higher elevations, closer to midwinter, and at temperatures that are colder than average given the location and time of year. Together, these findings support the hypothesis that sociality is a key strategy for coping with harsh environments. HIGHLIGHTSO_LIGrouping with others can be an important source of information about resources C_LIO_LIWe analyzed how flocking behaviour changes throughout winter in two bird species C_LIO_LIWe used the index of dispersion to quantify social clustering at a broad scale C_LIO_LIIn both species, social clustering increases in response to climate challenges C_LI

animal behavior and cognition↗
bioRxiv2022

Migration and the excess exposure of birds to human density in North America

Migratory species must cross a range of landscapes that are increasingly modified by humans. A key question is how migrating populations are responding to human-induced environmental change. Here, we model the spring migration dynamics of 63 bird species in North America to quantify their exposure to human population density. We find that most bird species have a negative navigational bias, suggesting that they attempt to avoid human-dense areas during migration, and yet they experience far greater human density during migration as compared to breeding. Species that experience excess human density during migration share several key traits: they tend to be nocturnal migrants, they start migrating through North America earlier in the year, and they tend to migrate longer distances. These findings underscore that birds are especially vulnerable to threats associated with human disturbance during migration, with predictable exposures that are often elevated by 2- to 3-fold during migration.

ecology↗
bioRxiv2022

Neurogenomic landscape of social status-dependent cooperative display behavior

The neurogenomic mechanisms mediating male-male reproductive cooperative behaviors are unknown. We leveraged extensive transcriptomic and behavioral data on a neotropical bird (Pipra filicauda) that perform cooperative courtship displays to understand these mechanisms. Cooperative display is modulated by testosterone, it promotes cooperation in non-territorial birds, but suppresses cooperation in territory holders. We sought to understand the neurogenomic underpinnings of these three related traits: social status, cooperative behavior, and testosterone phenotype. To do this, we profiled gene expression in 10 brain nuclei spanning the social decision-making network (SDMN), and two key endocrine tissues that regulate social behavior. We associated gene expression with each birds behavioral and endocrine profile derived from three years of repeated measures taken from free-living birds in the Ecuadorian Amazon. We found distinct landscapes of constitutive gene expression were associated with social status, testosterone phenotype, and cooperation, reflecting the modular organization and engagement of neuroendocrine tissues. Sex-steroid and neuropeptide signaling appeared to be important in mediating status-specific relationships between testosterone and cooperation, suggesting shared regulatory mechanisms with male aggressive and sexual behaviors. We also identified differentially regulated genes involved in cellular activity and synaptic potentiation, suggesting multiple mechanisms underpin these genomic states. Finally, we identified SDMN-wide gene expression differences between territorial and floater males that could form the basis of "status-specific" neurophysiological phenotypes, potentially mediated by testosterone and growth hormone. Overall, our findings provide new, systems-level insights into the mechanisms of cooperative behavior and suggest that differences in neurogenomic state are the basis for individual differences in social behavior.

evolutionary biology↗
bioRxiv2022

What causes bird-building collision risk? Seasonal dynamics and weather drivers

Bird-building collisions are a major source of wild bird mortality, with hundreds of millions of fatalities each year in the United States and Canada alone. Here, we use two decades of daily citizen-science monitoring to characterize day-to-day variation in building collisions and determine the factors that predict the highest risk times in two North American cities. We use these analyses to evaluate three potential causes of increased collision risk: heightened migration traffic during benign weather, increased navigational and flight errors during inclement weather, and increased errors in response to highly directional sunlight that enhances reflected images. The seasonal phenology of collisions was consistent across sites and years, with daily collision rates approximately two-fold higher in autumn as compared to spring. During both migration seasons, collision risk was best predicted by the weather conditions at dawn. In spring, peak collision risk occurs on days with warm temperatures, south winds, and a lack of precipitation at dawn. In autumn, peak collision occurs on days with cool temperatures, north winds, high atmospheric pressure, a lack of precipitation, and clear conditions with high visibility. Based on these results, we hypothesize that collisions are influenced by two main weather-driven mechanisms. First, benign weather at dawn with winds that are favorable for migration flight causes an increase in migration traffic in both spring and autumn, creating greater opportunity for collisions to occur. Second, for autumnal migrants, cold clear conditions may cause an additional increase in collision risk. We propose that these conditions may be particularly hazardous in autumn because of the high abundance of naive and diurnal migrants at that time of year. Our analysis also establishes that a relatively small proportion of days (15%) are responsible for 50% of the total collision mortality within a season, highlighting the importance of targeting mitigation strategies to the most hazardous times.

ecology↗
bioRxiv2022

The effect of sociality on competitive interactions among birds

Sociality can provide many benefits, including increased foraging success, reproductive opportunities, and defence against predation. How does sociality influence the dominance hierarchies of ecological competitors? Here, we address this question using a large citizen science dataset of competitive interactions among birds foraging at backyard feeders, representing a network of over 55,000 interactions among 68 common species. We first show that species differ in average group size (the number of conspecifics observed together) as a fundamental measure of sociality. When analyzing heterospecific competition, we find that sociality is inversely related to dominance. On average, a single individual from a solitary species is more likely to displace a size-matched opponent than a single individual from a social species. Yet, we find that social species gain an increase in their competitive advantage when in the presence of their conspecifics, which may occur as a result of dynamics within their groups. Finally, we show that more social species have relatively fewer dominance interactions with heterospecifics, and more with conspecifics. Overall, these results demonstrate that sociality can influence competition in ecological networks. More social species have decreased competitive ability as individuals, but they may gain competitive ability in groups.

animal behavior and cognition↗
bioRxiv2020

Reciprocal social ties drive stable cooperation within a social network

Social reciprocity is thought to be the most important driver of cooperation among non-kin, but its effects within complex social networks where individuals choose their partners have not been studied. Here, we test whether reciprocation can explain social dynamics in a bird species where males form coalitions to court females, the wire-tailed manakin (Pipra filicauda). In our study population, approximately a third of male-male social interactions involve one male leaving his territory to interact and display with the owner of another territory; this directional behaviour provides benefits to the recipient at a cost to the visiting male. We characterize social ties among pairs of territory holders according to the directionality of their interactions, and show here that territory holding males engaged in far more reciprocated (bidirectional) partnerships with other territory holders than expected by chance. Reciprocated partnerships were also stronger (i.e., the partners interacted more frequently) than non-reciprocated partnerships, controlling for spatial proximity of the territories. An individual-level analysis revealed that a males social contribution to a given partner was predictive of the number of social interactions he received from that same partner. Finally, we show that reciprocation predicted the long-term stability of social partnerships one year later. Together, these results demonstrate that reciprocity is associated with stability in complex social networks where partner choice is flexible. LAY SUMMARYO_ST_ABSWhen animals are free to choose their partners, how does reciprocity influence social dynamics?C_ST_ABSIn the wire-tailed manakin, males form coalitions with other males to help attract mates. We tracked male social networks and found that some males form reciprocal partnerships where each male leaves its territory to display at the others territory. These bidirectional partnerships are particularly strong and stable, indicating that reciprocity is associated with stability in complex social networks.

animal behavior and cognition↗
bioRxiv2020

Unpredictable hummingbirds: Flight path entropy is constrained by speed and wing loading

Unpredictable movement can provide an advantage when animals avoid predators and other threats. Previous studies have examined how varying environments can elicit unpredictable movement, but the intrinsic causes of complex, unpredictable behavior are not yet known. We addressed this question by analyzing >200 hours of flight performed by hummingbirds, a group of aerial specialists noted for their extreme agility and escape performance. We used information theory to calculate unpredictability based on the positional entropy of short flight sequences during 30-min and 2-hour trials. We show that a birds entropy is repeatable, with stable differences among individuals that are negatively correlated with wing loading: birds with lower wing loading are less predictable. Unpredictability is also positively correlated with a birds overall acceleration and rotational performance, and yet we find that moment-to-moment changes in acceleration and rotational velocities do not directly influence entropy. This indicates that biomechanical performance must share an underlying basis with a birds ability to combine maneuvers into unpredictable sequences. Contrary to expectations, hummingbirds achieve their highest entropy at relatively slow speeds, pointing to a fundamental trade-off whereby individuals must choose to be either fast or unpredictable.

animal behavior and cognition↗
bioRxiv2020

Flight morphology and visual obstruction predict collision risk in birds

Collisions with buildings are a major source of mortality for wild birds, but these instantaneous events are difficult to observe. As a result, the mechanistic causes of collision mortality are poorly understood. Here, we evaluate whether sensory and biomechanical traits can explain why some species are more collision-prone than others. We first examined concordance of species vulnerability estimates across previous North American studies to determine whether these estimates are repeatable, and whether vulnerability is more similar among closely-related species. We found moderate concordance and phylogenetic signal, indicating that some bird species are consistently more collision-prone than others. We next tested whether morphological traits related to flight performance and sensory guidance explain these differences among species. Our comparative analysis shows that two traits primarily predict collision vulnerability within passerines: relative beak length and relative wing length. Small passerine species with relatively short wings and those with relatively long beaks are more collision-prone, suggesting that greater maneuverability and obstructed vision contribute to risk. Together, these findings can help inform mitigation strategies and predict which species will be most at risk in other regions.

animal behavior and cognition↗
bioRxiv2019

Gender bias in research teams and the underrepresentation of women in science

Why are females still underrepresented in science? The social factors that affect career choices and trajectories are thought to be important but are poorly understood. We analyzed author gender in a sample of >61,000 scientific articles in the biological sciences to evaluate the factors that shape the formation of research teams. We find that authorship teams are more gender-assorted than expected by chance, with excess homotypic assortment accounting for up to 7% of published articles. One possible mechanism that could explain gender assortment and broader patterns of female representation is that women may focus on different research topics than men (i.e., the \"topic preference\" hypothesis). An alternative hypothesis is that researchers may consciously or unconsciously prefer to work within same-gender teams (the \"gender homophily\" hypothesis). Using network analysis, we find no evidence to support the topic preference hypothesis, because the topics of female-authored articles are no more similar to each other than expected within the broader research landscape. Instead, consistent with a model of moderate gender homophily, we find that the prevalence of matched-gender teams increases as a discipline moves towards gender parity. This can occur because latent preferences are more easily fulfilled in a gender-diverse environment. Finally, we show that female authors pay a substantial citation cost to work in gender-matched teams. Notably, the prevalence of homotypic assortment is predicted to increase in the future if more disciplines shift towards gender parity. These data indicate that social preferences can have important downstream consequences for the retention of women and other underrepresented groups in science.

scientific communication and education↗
bioRxiv2019

Extended hormone-phenotypes shape the structure, stability, and assortment of social networks

O_LISocial networks can vary in their organization and dynamics, with implications for ecological and evolutionary processes. Understanding the mechanisms that drive social network dynamics requires integrating individual-level biology with comparisons across multiple social networks. C_LIO_LITestosterone is a key mediator of vertebrate social behavior and can influence how individuals interact with social partners. Although the effects of testosterone on individual behavior are well established, no study has examined whether hormone-mediated behavior can scale up to shape the emergent properties of social networks. C_LIO_LIWe investigated the relationship between testosterone and social network dynamics in the wire-tailed manakin, a lekking bird species in which male-male social interactions form complex social networks. We used an automated proximity system to longitudinally monitor several leks and we quantified the social network structure at each lek. Our analysis examines three emergent properties of the networks: social specialization (the extent to which a network is partitioned into exclusive partnerships), network stability (the overall persistence of partnerships through time), and behavioral assortment (the tendency for like to associate with like). All three properties are expected to promote the evolution of cooperation. As the predictor, we analyzed the collective testosterone of males within each social network. C_LIO_LISocial networks that were composed of high-testosterone dominant males were less specialized, less stable, and had more negative behavioral assortment, after accounting for other factors. These results support our main hypothesis that individual-level hormone physiology can predict group-level network dynamics. We also observed that larger leks with more interacting individuals had more positive behavioral assortment, suggesting that small groups may constrain the processes of homophily and behavior-matching. C_LIO_LIOverall, these results provide evidence that hormone-mediated behavior can shape the broader architecture of social groups. Groups with high average testosterone exhibit social network properties that are predicted to impede the evolution of cooperation. C_LI

animal behavior and cognition↗
bioRxiv2019

Reciprocity and behavioral heterogeneity govern the stability of social networks

The dynamics of social networks can determine the transmission of information, the spread of diseases, and the evolution of behavior. Despite this broad importance, a general framework for predicting social network stability has not been proposed. Here, we present longitudinal data on the social dynamics of a cooperative bird species, the wire-tailed manakin, to evaluate the potential causes of temporal network stability. We find that when partners interact less frequently, and when the breadth of social connectedness within the network increases, the social network is subsequently less stable. Social connectivity was also negatively associated with the temporal persistence of coalition partnerships on an annual timescale. This negative association between connectivity and stability was surprising, especially given that individual manakins who were more connected also had more stable partnerships. This apparent paradox arises from a within-individual behavioral trade-off between partnership quantity and quality. Crucially, this trade-off is easily masked by behavioral variation among individuals. Using a simulation, we show that these results are explained by a simple model that combines among-individual behavioral heterogeneity and reciprocity within the network. As social networks become more connected, individuals face a trade-off between partnership quantity and maintenance. This model also demonstrates how among-individual behavioral heterogeneity, a ubiquitous feature of natural societies, can improve social stability. Together, these findings provide unifying principles that are expected to govern diverse social systems. Significance StatementIn animal societies, social partnerships form a dynamic network that can change over time. Why are some social network structures more stable than others? We addressed this question by studying a cooperative bird species in which social behavior is important for fitness, similar to humans. We found that stable social networks are characterized by more frequent interactions, but sparser connectivity throughout the network. Using a simulation, we show how both results can be explained by a simple model of reciprocity. These findings indicate that social stability is governed by a trade-off whereby individuals can either maintain a few high-quality partners, or increase partner number. This fundamental trade-off may govern the dynamics and stability of many societies, including in humans.

animal behavior and cognition↗
bioRxiv2019

How conspicuous are peacock eyespots and other colorful feathers in the eyes of mammalian predators?

Feathers perceived by humans to be vividly colorful are often presumed to be equally conspicuous to other mammals, and thus to present an enhanced predation risk. However, many mammals that prey on adult birds have dichromatic visual systems with only two types of color-sensitive visual receptors (one sensitive to ultraviolet light), rather than the three characteristic of humans and four of most birds. Thus, understanding how these predators perceive color requires quantitative visual modeling. Here, we use a combination of reflectance spectroscopy, multispectral imaging, color vision modelling and visual texture analysis to compare the visual signals available to conspecifics and to mammalian predators for multicolored feathers from the Indian peacock (Pavo cristatus) as well as red and yellow parrot feathers; we also take into account the effects of distance-dependent blurring due to visual acuity. When viewed by tetrachromatic birds against a background of green vegetation, most of the feathers studied had color and brightness contrasts similar to values previously found for ripe fruit. By contrast, when viewed by dichromat mammalian predators, the color and brightness contrasts of these feathers were only weakly detectable and often did not reach detection thresholds for typical viewing distances. We furthermore show that the peacocks erect train has undetectable color and brightness contrasts and visual textures when photographed against various foliage backgrounds. Given the similarity of photoreceptor sensitivities and feather reflectance properties across relevant species, these findings are consistent with many feathers of similar hue being inconspicuous, and in some cases potentially cryptic, in the eyes of their mammalian predators. These results suggest that many types of colorful feathers are likely to be cryptic to mammals while providing a communication channel perceptible to birds, while emphasizing the importance of understanding diverse sensory receivers in the evolution of animal coloration.

zoology↗