Hummingbirds rock bright colours to stave off unwanted male aggression: study
Researchers have found some female hummingbirds have evolved to look more like their male counterparts
The females of a species of hummingbirds have a unique evolutionary trick for keeping male bullies at a bay, a new study suggests.
Some female white-neck jacobin hummingbirds have evolved to look more like their male counterparts, adopting their bright and colourful plumage. And that's proving to be enough to keep them from being pecked at by aggressive male hummingbirds looking for food, according to a new study.
"Other hummingbirds see these blue-headed females and think they might be males, and they know that these males are bullies," lead author Jay Falk told As It Happens guest host Peter Armstrong.
"Seeing that, they basically think, 'OK, I'm going to stay away from them,' and that helps them experience less aggression."
Falk, a postdoctoral researcher at the University of Washington, led a study into the bird's plumage while he was a graduate student at the Cornell Lab of Ornithology. The research was published last week in the journal Current Biology.
White-neck jacobins come in two different looks. Historically, the males tend to have bright blue ornamented heads, along with white bellies and tails. Females tend to be a bit more drab, with green backs, and speckled grey throat and bellies.
But when Falk and his colleagues caught and tagged 120 female jacobins in Panama, they discovered that 30 per cent of the females were sporting the brighter blue colouring, rendering them indistinguishable from the males.
The researchers set up 28 feeders to observe the birds. Those with the male colouring were able to get more to eat, as they received less harassment from the males.
Falk and his team also observed how hummingbirds reacted to taxidermy versions of both females. The males showed less aggression toward the bright blue birds.
Advantages of being drab
While the brightly coloured females are able to collect food without having to worry about being pushed around by other hummingbirds, the look has its downsides.
The brightly coloured female birds will never be the belles of the ball, says Falk, because the males are more sexually attracted to the drab-looking females.
But Falk says that hasn't proved to be a problem, as the females he observed were still able to find mates — just maybe not their first choice.
The other downside is the bright colours can attract predators. Falk says the duller-looking females seem to be better hidden when sitting in their nest, while the bright jacobins are easier to spot.
"We think maybe the male-like females are escaping attacks when they're trying to find food, and it's possible that the drab females are basically able to escape predation at their nests," Falk said.
Falk isn't sure why some female jacobins develop this new look and others don't. As juveniles, both the males and females start out with bright colouring.
"Why they then shift so that most of the adult females are drab in colouration, that's something we still don't know," said Falk.
"It may go back to the whole nesting thing where, as an adult, you have to sit on this nest exposed to predators. Whereas when you're a juvenile, you don't have to do that whole nesting thing. And your main prerogative is probably just to get food, and maybe pretending to be a male is the way to do that."
Written by Philip Drost. Interview with Jay Falk produced by Kate Cornick.
