Conspicuous Plumage Does Not Increase Predation Risk: A Continent-Wide Test Using Model Songbirds

Abstract

The forces shaping female plumage color have long been debated but remain unresolved. Females may benefit from conspicuous colors but are also expected to suffer costs. Predation is one potential cost, but few studies have explicitly investigated the relationship between predation risk and coloration. The fairy-wrens show pronounced variation in female coloration and reside in a wide variety of habitats across Australasia. Species with more conspicuous females are found in denser habitats, suggesting that conspicuousness in open habitat increases vulnerability to predators. To test this, we measured attack rates on 3-D-printed models mimicking conspicuously colored males and females and dull females in eight different fairy-wren habitats across Australia. Attack rates were higher in open habitats and at higher latitudes. Contrary to our predictions, dull female models were attacked at similar rates to the conspicuous models. Further, the probability of attack in open habitats increased more for both types of female models than for the conspicuous male model. Across models, the degree of contrast (chromatic and achromatic) to environmental backgrounds was unrelated to predation rate. These findings do not support the long-standing hypothesis that conspicuous plumage, in isolation, is costly due to increased attraction of predators. Our results indicate that conspicuousness interacts with other factors in driving the evolution of plumage coloration.

A review of Gloger's rule, an ecogeographical rule of colour: definitions, interpretations and evidence

“…Ideally, testing the camouflage hypothesis should be done experimentally using models depicting realistic patterns of colour variation as observed along previously identified climatic gradients at different spatial scales and quantifying their ‘survival’. In this regard, widespread access to three‐dimensional (3D) printers will allow the deployment across different climatic or environmental gradients (Cain et al , ) of large numbers of models with realistic colours based on the visual abilities of predators (Delhey et al , ).…”

Evolutionary drivers of seasonal plumage colours: colour change by moult correlates with sexual selection, predation risk and seasonality across passerines

“…Seasonal plumage colours have been lost in two species, the lovely and white‐shouldered fairy‐wrens ( M. amabilis and M. alboscapulatus; Fan et al ). Both species have high annual survival rates (Leitão et al ) and live in the tropics, where predation risk on fairy‐wrens appears to be relatively low (Cain et al ) and where reduced seasonality may favour less well‐defined breeding schedules (Leitão et al ). In purple‐crowned fairy‐wrens ( M. coronatus ), seasonal plumage colours appear to be in the process of being lost due to a lack of strong sexual selection (Kingma et al ; Fan et al ) and a lack of a defined breeding season, as the species can breed year‐round in response to rainfall (Hidalgo Aranzamendi et al ).…”

Revealing The Colourful Side of Birds: Spatial Distribution of Conspicuous Plumage Colours on The Body of Australian Birds

“…To obtain a general index of conspicuousness I averaged the estimates of contrast against both background types (Delhey et al 2017). While this does not capture the entire variety of background colours, it is largely representative of the rather limited palette of background colours present in terrestrial environments (Delhey et al 2013; Cain et al 2019). Indeed, values of conspicuousness were highly correlated (males: r = 0.97, p < 0.001; females: r =0.96, p < 0.001) with those obtained using reflectance spectra of natural backgrounds of European forests (Delhey et al 2010).…”