Scientists solve huge humpback mystery – with the help of a tiny backpack

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The world’s largest humpback has been hidden for centuries – and scientists have only discovered the species is different from another giant species after attaching tiny backpacks to humps to understand migration patterns.

Along the way, researchers also identified the longest humpback migration journey, which spans a round trip of 5,200 miles (8,368-kilometers), or about the distance between New York City and Buenos Aires.

There have been questions about South American giant humps since naturalist Charles Darwin first saw them in 1834 during his voyage aboard the HMS Beagle.

Darwin noticed the birds, which are about eight times the size of typical hummingbirds, breeding along the Pacific coast of Chile, but then they seemed to disappear completely after breeding. He speculated that the giant humps moved to the Atacama Desert region, which is located in the north of Chile.

Now, new research has shown that there are two separate species of giant humpbacks in South America – the northern giant humpback that lives year-round in the Andes, and the southern migratory giant humpback – and they are evolving separately with the millions of years.

A southern giant humpback is seen flying from its breeding grounds in central Chile.  - Chris Witt

A southern giant humpback is seen flying from its breeding grounds in central Chile. – Chris Witt

A new study describing the birds appeared Monday in the journal Proceedings of the National Academy of Sciences.

“There aren’t many animal migrations of large, charismatic species that are still unknown, but that was the case for the southern giant humpback,” said lead study author Jessie Williamson, a National Science Foundation Postdoctoral Fellow and Rose Postdoctoral Fellow. at Cornell. Ornithological Laboratory in Ithaca, New York. “We wanted to finally solve this mystery.”

Designing backpacks for your hips

Giant hummingbirds differ from the hundreds of other hummingbird species in many other ways.

“Everything about the giants is anomalous – not only are they much bigger (twice or more) than the second largest humpback – but their wing beats and their hearts are much slower,” Williamson said. “And their wings are proportionately longer, so they look completely unique in flight – almost like a hovering swift.”

The swift is a medium-sized, fast-flying bird that is included in the Apodidae family, which also includes doves.

But studying humps, no matter their size, is hard work. The team worked with local landowners and village residents throughout Peru and Chile during fieldwork.

“It is very challenging to catch Big Birds,” study co-author Emil Bautista, a researcher at the Centro de Ornitología y Biodiversidad in Lima, said in a statement. “They look at everything, and they know their territory very well. We had to be strategic in choosing sites for our nets. If Giant Hummingbirds see something unusual, they will not visit that location. They are more alert than other birds.”

The research team spent nine months camping in rural parts of Chile and Peru, working from sea level to the steep cactus slopes of the Andes and going without electricity or running water for weeks, Williamson said.

Williamson designed a backpack harness, using a type of jewelry cord to attach a microtracking device to 57 humps in Chile.

“It took two seasons of trial and error to design appropriate back harnesses for giant humps, including practicing harness design on a stuffed hump finger puppet … with a fake paper mache geolocator device, as well as much consultation with colleagues who experience a little tracking. migratory birds,” Williamson said.

A giant southern humpback has been fitted with a tiny geolocator tracking device like a backpack in central Chile.  - Jessie WilliamsonA giant southern humpback has been fitted with a tiny geolocator tracking device like a backpack in central Chile.  - Jessie Williamson

A giant southern humpback has been fitted with a tiny geolocator tracking device like a backpack in central Chile. – Jessie Williamson

The geolocator backpacks weighed 0.3 grams and were designed to be small and light enough to not interfere with the birds’ flight style.

Williamson published a paper describing her design and how to safely attach it to hips in the Journal of Avian Biology in June 2021.

“Humps are challenging to work with because they are light with long wings and short legs. They are nature’s tiny acrobats,” she said.

But it wasn’t enough to catch the birds, attach the backpacks and release them – the birds had to be caught again for the team to collect the data.

The researchers were able to retrieve data from eight of the geolocators by recapturing the birds using fine mesh nets called “mist nets,” commonly used by ornithologists, Williamson said.

What the team discovered is that southern migratory giant humps are like human mountaineers.

High-altitude bird flights

The geolocator data showed that migrating giant humps can rise from sea level to more than 13,000 feet (3,962 meters) in altitude, and their travels have taken them as far north as the Peruvian Andes.

But the birds do not fly directly to these high altitudes. Instead, like mountaineers, they pause during their ascent for days at a time to allow their blood and lungs to adjust to lower oxygen levels.

By tracking the birds’ migration with geolocators and satellite transmitters, scientists have discovered what they believe to be the longest known hummingbird migration, spanning 5,200 miles (8,368 kilometers) from the coast of Chile up to the Andes in Peru and back.

As the researchers studied the birds and compared them with genetic data from museum specimens, they realized that there were two types of giant hummingbirds.

“Nobody knew where migratory giant humps go because they were hidden among the non-migratory giant humps,” said senior study author Christopher Witt, professor of biology and director of the Museum of of Southwestern Biology at the University of New Mexico, in a statement. “The two types of giant hummingbird look almost identical – for centuries ornithologists and birders did not notice that they were different. We couldn’t have figured this out without the miniaturized trackers.”

The difference between the two species is probably due to a change in migratory behavior. By studying museum species, including a 154-year-old specimen, the researchers realized that the two types of giant hummingbirds had been evolving separately for about 3 million years.

“They are as different from each other as chimpanzees are from bonobos,” Witt said. “The two species overlap in their high-elevation wintering grounds. It is remarkable that until now no one understood the mystery of the Great Coot, but that these two species were separated by millions of years.”

The northern giant humpback, which lives in the high Andes all year round, has a different lung and blood capacity compared to the southern giant humpback.

After realizing that the two birds were completely different species, the study team named the giant northern Patagona humpback chaski, a nod to chaskis, the Quecha word for messengers, of the Inca Empire. Quecha is a group of indigenous languages ​​spoken throughout Peru and neighboring countries.

“Chaski runners were definite sprinters, capable of speed and endurance on steep slopes, in part due to high-capacity lungs and intense aerobic training at altitude,” the authors wrote in the study.

A new bird mystery emerges

The researchers reported that both populations of giant hummingbirds are stable, and some can even be seen enjoying nectar from backyard feeders.

A giant hump is shown to the south ready for takeoff.  - Chris WittA giant hump is shown to the south ready for takeoff.  - Chris Witt

A giant hump is shown to the south ready for takeoff. – Chris Witt

Now that the two distinct species have been confirmed, the team wants to better understand how the populations interact, especially when they live in the same parts of the Andes during the winter.

“We need to figure out where these two forms meet and how they interact,” Witt said. “Do they compete, is one dominant over the other, how might they partition resources, and do they mix or spatially segregate within the winter range? Lots of interesting questions to follow!”

Williamson also wants to work with botanists to understand how the birds’ migration patterns may coincide with the flowering plants the birds use for sustenance on their journeys.

“I’m very interested in how Southern Great Hummingbirds undergo such large changes in elevation during migration,” Williamson said. “They are like miniature mountain climbers. How do they change their physiology to facilitate these movements?”

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