Life Science Environment Tweet of the day: Female hummingbirds dress as males to avoid harassment

Tweet of the day: Female hummingbirds dress as males to avoid harassment

A female white-necked Jacobin hummingbird decked out in male colours. Photo: Irene Mendez Cruz
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A couple of years ago there was a story about a young university student in Arizona who dressed as a man to avoid harassment on the street.

This involved wearing baggy clothes and drawing on a fake beard.

She told the college paper that it was a bit of a joke, but it seemed to work.

A recent study found that a species of hummingbird does exactly the same thing.

About 20 per cent of all female white-necked Jacobin hummingbirds dress up as flashy males, to avoid harassment and violent attack when they’re feeding off flowers.

It’s possible this behaviour has been going on for hundreds, even  thousands, of years.

But it’s only now that scientists have twigged to the cross-dressing strategy.

What a plight … getting body-slammed in flight

Ordinarily, the female plumage of white-necked Jacobins is a relatively dull grey and green.

They’re designed that way as camouflage when sitting on the nest in the Panamanian forest.

Keeping nests low key means eggs and chicks are less likely to be carried off by predators.

But perhaps even more crucially, hummingbirds have to eat several times an hour. In fact, they are routinely just a few hours away from starvation.

Females acquire greener colours for camouflage. Photo: Sam May/Creative Commons

The life of a female Jacobin hummingbird in particular is one of endless toil, especially when breeding.

She is, in effect, saddled with a deadbeat dad who disappears from the scene as soon as he’s knocked up mum.

There’s the nest to weave: Many hours of work. Sitting on the nest is interrupted several times an hour by the need to feed on nectar.

The problem is, feeding is often competitive and aggressive – and the males (those deadbeat dads!) will body slam and peck the drab females mid-flight, sometimes killing them.

An experiment by researchers from the Cornell Lab of Ornithology and Smithsonian Tropical Research Institute found that females sporting the male colours – iridescent blue heads, bright white tails and white bellies – were far less harassed. Talk about a boys’ club.

How does it happen?

As juveniles, both sexes have the flashy blue plumage.

But as the females mature and come of breeding age, the bright colours fade and the drab camouflage emerges.

The researchers can’t explain why one in five females hold on to their male-looking plumage.

Is there a genetic factor, or do the birds somehow have a choice in the matter? If so, what’s the mechanism?

Another idea is that environmental factors are at play.

If the cross-dressing is a more recent development, then somehow climate change or habitat loss might play a hand.

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