June 4 (UPI) -- Scientists are finally beginning to understand how and why birds flock.
In a new study, published Tuesday in the journal Evolutionary Biology, scientists analyzed the flocking mechanics of four shorebirds of varying sizes: the dunlin, short-billed dowitcher, American avocet and marbled godwit.
After studying nearly 100 hours of video footage, researchers identified a new flying formation called the compound V-formation. Scientists estimate the formation offers the birds aerodynamic advantage and predator protection.
The compound V-formation is a combination of the cluster formation and the more famous V-formation. The cluster formation is a 3D cloud shape with no rigid structure. It is most often demonstrated by flocks of pigeons and crows. The V-formation is the flock shape commonly seen in North American skies each fall and spring as Canadian geese migrate overhead.
"A flying bird creates downward-moving air immediately behind it and upward-moving air just beyond its wingspan on the left and right," Tyson Hedrick, a professor of biology at the University of North Carolina, Chapel Hill, said in a news release. "Taking advantage of this upward-moving air is all about positioning, and birds in the simple-V formation and compound-V formation are positioned correctly for aerodynamic advantage."
To better understand the mechanics of the compound V-formation, Hedrick and his research partners converted their video footage into 3D computer models. With the help of their digital reconstructions, scientists were able to measure the positioning of the birds in each flock, as well as the flight speeds and flapping frequencies of individual birds. The research team analyzed flocks ranging in size from 100 to 1,000 birds.
"We thought we would find a trend in flock organization related to how large or small the different birds were," Hedrick said. "Instead we saw that regardless of size, all these birds flew in the same formation -- one that might let them get an aerodynamic benefit while flying in large groups, aiding their long-distance migration."
Though the four bird species have been evolutionarily separate for 50 million years, each of them utilize similar flocking dynamics, taking on some combination of a cluster and V-formation when flocking. Though the birds typically only flocked with their own species, scientists observed godwits and dowitchers joining one another's flocks.
Despite the different size, speeds and flapping frequencies of the four bird species, scientists found individuals positioned themselves similarly: usually one wingspan to the side of their neighbor and between a half to one-and-a-half wingspans back from the bird just ahead.