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Muscle structure and body size predict the athletic performance of Olympic athletes, such as sprinters. The same, it appears, is true of wild seabirds that can commute hundreds of kilometres a day to find food, according to a recent paper by scientists from 麻豆AV and Colgate universities published in the .

The researchers studied a colony of small gulls, known as black-legged kittiwakes, that breed and nest in an abandoned radar tower on Middleton Island, Alaska. They attached GPS-accelerometers鈥擣itbit for birds -- onto kittiwakes to track their flight performance, discovering that they sometimes travel as far as 250 km a day to find food for their offspring.

By combining data from the GPS tracker with minute muscle samples from some of the birds, the researchers found that, despite beating their wings less frequently, birds with larger muscle fibres were able to fly as fast as those with smaller fibres. The team also found that birds that flew faster had a higher number of nuclei 鈥� which produce the proteins to power flight - in their muscle cells, allowing the birds to activate more muscle fibres to power their flight.

Exercising to build muscle

Athletes exercise to maintain muscle tone. The same may be happening with kittiwakes, with those individuals that exercise the most鈥攖hat is, fly the most鈥攈aving better developed muscles than those that move less.

鈥淭hese birds are no couch potatoes. Clearly, like elite athletes, they need to have the appropriate body and muscles in excellent shape to be able to travel over these long distances to feed their offspring. But there鈥檚 been a long-standing biological question about why some individual birds perform so much better than others,鈥� says Kyle Elliott, an assistant professor in 麻豆AV鈥檚 Dept. of Natural Resource Sciences in the Bieler School of Environment, and co-author of the study. 鈥淧ast studies have focused on hormone levels, body mass or levels of red blood cells as a predictor of flight performance. We found that muscle structure and body mass together predict performance."

Using miniature smart phones to track wild birds

鈥淲ith the data from the GPS-accelerometers, we can understand a lot about these birds, like where they鈥檙e going to find food, how fast they鈥檙e flying, and how frequently they鈥檙e beating their wings in flight,鈥� says Kristen Lalla, the first author on the paper, which she co-authored as an undergraduate student under the supervision of Elliott. 鈥淚n the past, one of the challenges of measuring muscle structure in small birds was that it usually requires biopsying the muscle.鈥�

The Gulf of Alaska experienced the largest marine heat wave on record during the study in 2017, and kittiwakes were forced to forage four to five times farther away than pre-heatwave. The researchers are excited to continue the study and determine how muscle structure and flight performance vary when conditions are a little less challenging.

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To read: 鈥淎ccelerometry predicts muscle ultrastructure and flight capabilities in a wild bird鈥� by Kristen M. Lalla et al in the
doi: 10.1242/jeb.234104

The research was funded by the Natural Sciences and Engineering Research Council.

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