Hundreds of thousands of years ago, a couple of birds with exotic tastes had an interspecies tryst.

Now, a Canadian-led team of scientists has confirmed their descendants are a new species that arose from the hybridization of two separate parent species — which happens very rarely in birds, as far as we know.

The golden-crowned manakin, a rare species found in Brazil's Amazon rainforest, is a descendent of hybridization between the snow-capped manakin and the opal-crowned manakin, according to a team led by Alfredo Barrera-Guzman, who conducted the research during his PhD at the University of Toronto Scarborough.

The crowns of stuffed specimens of the opal-crowned, yellow-crowned and snow-capped manakin show the differences in the colours of their crowns. In the opal-crowned and snow-capped manakins, the colour comes from physical patterns on the feathers. (Jason Weir)

And it appears that after becoming isolated from the parent species, the golden-crowned manakin evolved a very unique feature – bright yellow feathers on its forehead that are distinctly different from the bright white ones on the snow-capped manakin and iridescent bluish feathers on the opal-crowned manakin.

Jason Weir, co-author of the paper published Monday in the journal Proceedings of the National Academy of Sciences, said people often think of hybridization as something that erodes diversity. But this is an example of hybridization generating more of it.

"That's really exciting," said Weir, a professor of ecology and evolutionary biology at the University of Toronto Scarborough who supervised Barrera-Guzman.

The study's lead author is Alfredo Barrera-Guzman, who conducted the research during his PhD at the University of Toronto Scarborough. (Jason Weir/University of Toronto)

Not seen for 40 years

The golden-crowned manakin was a new species discovered in 1957 and not seen again until 2002. Its rarity led at least one biologist to propose the birds could be a rare hybrid.

"I've always been curious about this," Weir said. "If it represented hybrids, why would it be yellow? It's so different from the parent species."

In order to solve the mystery, the researchers made several trips to the Amazon between 2012 and 2015 to capture all three species and take blood samples for DNA analysis.

Weir said during those expeditions, the researchers had two close encounters with jaguars, wound up covered in as many as 300 ticks at once, found botfly larvae growing in their skin, and accidentally caught a huge anaconda in their bird net.

Feathers of the opal-crowned, snow-capped and yellow-crowned manakins show how the colours reflect light. Hybrids of opal-crowned and snow-capped manakins have dull white caps. The researchers think the yellow colour evolved to compensate, because females found it more attractive.

For their troubles, they managed to catch 144 birds and collect their DNA, which was analyzed alongside DNA from museum specimens.

Using a combination of genetic analysis and computer modelling, the researchers found the golden-crowned manakin got 80 per cent of its genome from the opal-crowned manakin and 20 per cent from the snowy-capped.

The data suggested that the two species first mated 180,000 years ago, give or take about 100,000 years, and may have interbred for tens of thousands of years. But the researchers think that sometime during the last three glacial periods in the past few hundred thousand years, large rivers may have blocked the hybrids from mixing with the parent species, and the whole population was able to breed only with itself.

Sexy yellow

So where did the yellow crown come from?

Weir says the bright crowns of the snowy-capped and opal-crowned manakins come not from pigments, but from distinct physical patterns on their feathers that reflect light.

The patterns are very different in the two species, but hybrids get something halfway in between that is dull and not very reflective. The researchers know that because they've found an area of the Brazilian rainforest where snowy-capped and opal-crowned manakins still occasionally interbreed, and they've captured a couple of rare hybrids, who have very dull white crowns.

The researchers think because that isn't as attractive to females, natural selection led to yellow pigments – found in feathers on other parts of the bird's body – accumulating in the crown feathers of the yellow-crowned manakin over time.

University of Toronto ecology professor Jason Weir and his team made several trips to the Amazon between 2012 and 2015 to catch all three manakin species and take DNA samples. Here, Weir extracts a bird caught in a mist net during the 2012 expedition. (Jason Weir/University of Toronto Scarborough)

While researchers have previously found very few hybrid species, Weir says new technology has made it possible to do much more detailed genetic analysis than in the past.

"It's possible that we're going to find that they're much more common than we realized," he added. "Or we might find out that they're rare and we happened to be lucky in finding this one."