Fear of death is a fairly strong motivator. And yet, animals get eaten all the time despite constant vigilance for predators in their midst. The problem is that animals are multi-purpose machines: they eat, they mate, they hunt for food and mates, and so on, and these activities can get in the way of spying for predators. This trade-off is particularly acute for males with conspicuous sexual signals. But as shown by Alexandra McQueen and her colleagues from Monash University in Victoria and the Australian National University in Canberra, male birds can adapt their behaviors to mitigate the risks of their flashy sexuality. Even more striking, so too can their drab neighbors.
Superb fairy-wrens are small Australian birds that live in social groups composed of a mating pair and a handful of male helpers. While females and non-mating males are an inconspicuous dull brown, mating males sport a plumage of pure blue brilliance. This matters, because not only do these fancy guys get the girl they're with (at least socially), but their blueness also attracts females from other territories as extra-pair mates. But being attractive is a double-edged sword. On the one hand, greater visibility leads to more offspring sired. On the other hand, a bright blue male is an easier target to visual predators than a dull brown one. And the blue males seem to be aware of this.
McQueen and her colleagues found striking differences in the behaviors of blue and brown birds. While brown birds spent most of their time foraging in open landscape, their blue counterparts eschewed the open space and opted instead to forage in or near shrubbery. In addition, blue birds spent considerably more time scanning the landscape, presumably to aid in predator detection. And when the team spooked the birds by playing a recording that signaled an alarm, the blue birds were far more likely to flee into cover and they remained hidden for more than twice as long as brown birds.
These results suggest that blue birds assess their own predation risk and act to reduce it. What's more surprising is that brown birds nearby also take advantage of the blue bird's caution. They spent less time searching for predators if a blue bird was around and also spent less time hiding in the bushes after they were spooked by the alarm.
I'm reminded of the old joke about a pair of campers and an attacking bear. While one camper laces up his running shoes, his friend questions why, as he'll be outrun by the bear anyway. The first responds that he doesn't need to outrun the bear, just him. Just like this camper, brown birds seem to distinguish absolute and relative risks. When on their own, they flee from perceived danger. But when in the presence of more conspicuous bait, brown birds can be more relaxed. They seem to understand that they don't need to outfly the predator, just the snazzy player in the blue suit.
