To shield themselves from the cold, many birds use a unique snuggling position called the "backrest." They cock their head back and to the side and tuck their beak under their wings.

Scientists at Deakin University decided to take a deeper look at backrest behavior among nine bird species. They found birds with larger beaks exhibited backrest behavior more often and for longer periods of time.

Scientists surveyed hours of footage of shorebirds, filmed during winter, with temperatures ranging from 10 to 40 degrees Fahrenheit.

"When we looked at the footage, we found the red-necked avocet, which has the longest relative bill length, had the highest use of the backrest posture, while the masked lapwing, with the smallest relative bill length, used it the least," Julia Ryeland, field researcher and Deakin honors student, said in a news release.

The new research, detailed in the journal Functional Ecology, is a reminder that all physiological adaptations come with a tradeoff.

"This means that while these birds have developed larger beaks to help them forage for food, it actually has a negative side effect in that they need to spend more time keeping this equipment protected from the cold," said Matthew Symonds, deputy director at Deakin's Center for Integrative Ecology. "This then lessens their time available for things like food gathering and keeping an eye out for predators. It's an unexpected cost of having a larger bill."

A bird's bill allow for heat loss, which explains why birds in northern climes have mostly evolved smaller beaks.