Abstract
Increased predation risk is considered a cost of having conspicuous colours, affecting the anti-predator behaviour of colourful animals. However, this is difficult to test, as individual factors often covary with colour and behaviour. We used alarm call playback and behavioural observations to assess whether individual birds adjust their response to risk according to their plumage colour. Male superb fairy-wrens (Malurus cyaneus) change from a dull brown to conspicuous blue plumage each year, allowing the behaviour of different coloured birds to be compared while controlling for within-individual effects. Because the timing of colour change varies among males, blue and brown birds can also be compared at the same time of year, controlling for seasonal effects on behaviour. While blue, fairy-wrens fled more often in response to alarm calls, and took longer to emerge from cover. Blue fairy-wrens also spent more time foraging in cover and being vigilant. Group members appeared to benefit from the presence of blue males, as they reduced their response to alarms, and allocated less time to sentinel behaviour when a blue male was close by. We suggest that fairy-wrens perceive themselves to be at a higher risk of predation while in conspicuous plumage and adjust their behaviour accordingly.
Highlights
Higher predation risk is considered a key cost borne by conspicuously coloured animals, as this is a logical outcome of being readily detected in the natural environment ([1], but see aposematic colours; [2])
Superb fairy-wrens behave as though they perceive themselves to be at increased risk of predation while in conspicuous blue plumage
Blue males responded more strongly to alarm playbacks than brown birds; they were more likely to flee in response to low-danger alarms, and tended to take longer to emerge from cover after fleeing in response to high-danger alarms
Summary
Higher predation risk is considered a key cost borne by conspicuously coloured animals, as this is a logical outcome of being readily detected in the natural environment ([1], but see aposematic colours; [2]). These males may differ in factors such as body condition, age, personality and likelihood of future reproductive success [21,28,29], which have been shown to affect the propensity to take risks [30,31,32] To address these issues, it is helpful to test for changes in conspicuousness and anti-predator behaviour within individuals. Male fairywrens moult twice per year, alternating between cryptic brown, and conspicuous blue-and-black plumage (‘blue plumage’), while females have brown plumage year-round [34,35] This allows the behaviour of blue and brown fairywrens to be compared while controlling for individual differences in behaviour due to dominance, personality and other factors. Because individual males differ in the time they undergo colour change [36,37], we were able to compare different-coloured fairy-wrens at the same time of year, allowing us to control for possible seasonal effects on behaviour
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