How Did Seabirds Develop the Ability to Cruise Through Air and Water? New Insights Revealed

Seabirds are a type of bird that makes it's living primarily from the ocean, beyond the seashore or surf zone. They are beautifully adapted for life in the ocean.

Generally, seabirds have dense, waterproof feathers and fat layers that serve as a desalinization system to remove excess salt.

According to Audubon, California, most seabirds can live up to 50 years and breeds by age 5-10 years old. Scientists believe that this characteristic is an evolutionary strategy to cope with the ocean environment and give them a chance to spend several years learning how to forage their food over many seasons before breeding.

Additionally, it allows the adult seabird to successfully rear their young, who also reached their productive years.

But scientists have always been curious as to how they developed their ability to cruise both in the air and water. A group of scientists recently published a new insight in the open-access journal eLife on how seabirds develop such ability.

Unraveling the Mystery of the Pacific Northwest Seabirds

Seabirds such as puffins, murres, and their relatives belong to the Alcidae family, which produces efficient propulsive wakes while flying and swimming. By doing so, they only require low amounts of metabolic energy when creating the force that allows them to move in both air and water.

Moreover, the findings suggest that alcids have been optimized for movement in a range of environments over the course of their evolution.

First author Anthony Lapsansky, a Ph.D. candidate at the Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana, explained that birds that use their wings to fly in both air and water are expected to fly poorly in both environments compared to other birds who stick to one environment.

"In other words, these jacks-of-all-trades should be the masters of none," says Lapsaanky.

Interestingly, this does not seem to be the case for alcids as both their aerial and aquatic performance contradict this notion. This prompted the researchers to investigate it further.

To do so, the researchers tested whether alcids show 'efficient Strouhal numbers' when flying in air and water. The Strouhal number describes the frequency of the animals producing pulses of force with the appendages that seabirds use to power its movement.

They found that only a narrow range of Strouhal numbers are efficient. The birds waste its energy as it flaps its wings too fast or too slow for a given amplitude and flight speed. That means that selection has tuned seabirds to exhibit efficient flapping and swimming movements.

Flying Technique of Seabirds in Air and Water

Lapsansky and his team were also interested to know whether seabirds fly in air and water using their muscles in the same way in both environments.

"Muscles typically consist of fibers which are tuned for specific activities, but this hardly seems possible when the same muscles are used for movement in two drastically different environments," said Lapsansky.

The researchers think that alcids maintain efficient Strouhal numbers and consistent stroke velocities when flying in both environments. This allows the seabirds to mitigate the costs of being able to cruise through air and water.

They used videography to measure the wing movements of four species of alcids with different masses and represent distant branches of the alcid family tree. Their results showed that these birds cruise at Strouhal numbers between 0.10 and 0.40 in both air and water, similar to those birds who stick in either of the two environments.

Their findings suggest that evolution has shaped alcid flight in response to competing for environmental demands in air and water, concludes Bret Tobalske, Professor and Director of the Field Research Station at Fort Missoula, Division of Biological Sciences, University of Montana and the study's senior author.