Hummingbirds’ great migration that eluded Charles Darwin

Charles Darwin did not know where the hummingbirds came from. In 1834, he saw them flit past, sometimes hovering, and surprisingly big.

Giant hummingbirds drink water during a stop in Colombia. Picture: AFP

Charles Darwin did not know where the hummingbirds came from. In 1834, when his ship the Beagle anchored in central Chile, he saw them flit past, sometimes hovering, and surprisingly big.

They “had arrived in numbers, a little before the vernal equinox”, the naturalist wrote. But from where? All he knew was this bird, the largest of its kind, “comes from the parched deserts of the north, probably for the purpose of breeding”.

Almost two centuries later, a study has finally established how far north and how tired the birds must have been in their quest for breeding. By putting miniature backpack tracking devices on the giant hummingbird, researchers have shown that they engage in one of the great migrations of the animal world – travelling 8000km and climbing more than 4000m into the heart of the Andes.

They also found an explanation for why the hummingbird’s migration had not been properly understood until now: it is one of two species. Jessie Williamson, from the Cornell Lab of Ornithology, said that she started looking at the birds because it was so odd that we did not know what they did for half the year. “There had been this low-hanging fruit in the literature,” she said. “No one had known the mystery of where these things disappeared to after they left their breeding grounds in Chile.”

Ordinarily, you would capture a bird and then track it. Although these hummingbirds are big by hummingbird standards – about eight times the mass of an average hummingbird – they are still ­pretty small. So too, increasingly, are trackers.

“I had been interested in tracking bird migration with tiny devices,” Ms Williamson said. “We had a joke, that these things are ­almost small enough nowadays you could put them on a hummingbird. Then we realised, that was true.” So they did.

The resulting route, described in the journal Proceedings of the National Academy of Sciences, was “totally unexpected”. When they arrived in Chile, they had ­indeed come, as Darwin suggested, from the parched deserts of the north – but only because they passed through the Atacama after feeding in the high mountains of the even further north.

Their journey rivals the longest known migration of a hummingbird – also around 8000km. However, it arguably exceeds its ­intrepidity. To reach their summer feeding grounds, they climb to altitudes with half the oxygen they had at sea level, pausing for days en route apparently to help them acclimatise.

When the researchers ­sequenced its genome, they found that it appeared to have adaptations in its blood that could assist with this mountaineering. They also found something even more significant: the southern giant hummingbird is a different species from the one found in the north.

This explained how their ­arrival in Peru had not been spotted. “The reason no one had worked it out is the two look ­almost identical.” When they reached their destination, they just blended in with the northern hummingbird, making it hard to disentangle which were migrants. Why though? Why go all that way? And why split into two such similar-looking species? Ms Williamson said that solving the mysteries of the giant hummingbird could fill the rest of her career – and that is fine by her.

“This is my favourite hummingbird. It’s a fantastic species … or, a fantastic two species.

“Most hummingbirds are just flashy. This is like the elephant of hummingbirds.”

THE TIMES