Like a peloton of cyclists gaming the harsh realities of aerodynamics, birds flying together in formation can save substantial amounts of energy. But what's good for the goose isn't necessarily good for the gander, with scientists finding that for pairs of homing pigeons this approach actually costs them energy instead. So what could be the reasons for this common co-dependency?

Why homing pigeons will often fly in tandem is a question that has puzzled animal scientists for decades. There are a few theories around why this might be, and looking to shed further light on the topic, researchers at the University of Oxfords Department of Zoology decided to look into what it means for their energy expenditure.

This meant equipping homing pigeons with GPS tags and accelerometers to track how their wingbeat patterns differed between when they flew in pairs and when they flew solo. The researchers found that when a pair of homing pigeons flew together on a 7-km (4.3-mi) journey, both flapped at a rate of one extra wingbeat per second, but with little gained in terms of their speed through the air.

"The results of this study were completely unexpected," said lead-author, Dr Lucy Taylor. "Energy is the currency of life so it's astonishing that the birds are prepared to pay a substantial energetic cost to fly together."

According to the researchers, these extra flaps are like Usain Bolt running a 100-meter sprint, but fitting in an extra step every second. The reasons for this may just be as simple as maintaining stable flight.

"Imagine trying to coordinate with and avoid hitting another small object traveling at around 44 miles per hour," says Taylor. "This is nearly two times faster than an Olympic sprinter, and the birds can move up and down as well as left and right. For a pigeon, flapping your wings faster will both give you faster reactions and greater control over your movements, and will help keep your head stable making it easier to track where the other bird is."

Even though flying this way required more energy on part of the homing pigeons, the researchers say they consistently chose to do so. The team found that when joining forces, the pairs of homing pigeons exhibited far greater homing accuracy, reducing their flight distances by 7 percent and time traveled by 9 percent, meaning that they likely save energy over the journey anyway.

This homing accuracy theory has been bandied about for years, along with the idea that flying in numbers simply provides better protection from predators. It's just that now scientists have a new understanding of the cost-benefit analysis at play, along with flight behaviors that are unique among birds that like to travel in company.

The research was published in the journal PLOS Biology.

Source: PLOS via ScienceDaily