Migrating Songbirds Make Startling Altitude Adjustments

Anyone who's ever flown knows the situation where it gets bumpy and the captain tells the passengers that the crew will try to seek out a smoother altitude. It turns out migrating songbirds do a lot of their own altitude shifting, only a lot more than a typical airline flight, for reasons not yet known.

Songbirds can log lots of miles during their annual migrations -- many thousands in a given year. Such journeys require a great expense of energy, and scientists have long held the notion that the birds likely pick a nice cruising altitude with good winds and keep with it, rather than expend precious energy going higher and lower in search of the perfect journey.

Now, though, in the first recorded full-altitude flight data for migrating songbirds, those assumptions have been challenged.

University of Michigan-Dearborn Assistant Professor of Biology Melissa Bowlin tracked a group of Swainson's thrushes she'd equipped with radio transmitters. The hardware on the birds recorded both air pressure and temperature, allowing Bowlin to determine their altitudes.

What she found came as a surprise. During their nighttime flights, the songbirds were making frequent, dramatic in-flight altitude adjustments of more than 328 feet (100 meters).

"We expected the birds to behave like commercial aircraft, ascending to a particular altitude, leveling off and cruising near that altitude, and then coming down just before they landed," said Bowlin, in a press release.

"I was shocked when I made the first graph for the first bird, and thought it was an anomaly -- maybe the transmitters weren't working correctly," she said. "The more data we obtained, however, the more often we saw the up-and-down pattern to the birds' flight."

Of course, the big question now concerns why the songbirds are doing so much adjusting. The answer isn't yet known, Bowlin said. Perhaps, she surmised, they are adjusting to city lights or the warmer air that metropolises create, adapting to small changes in the atmosphere, or simply taking some approach to the trip that science hasn't yet figured out.

Bowlin points to both bird welfare and safer aviation as reasons to learn more about migratory birds' in-flight decisions.

"Every year, $1.28 billion is lost globally as a result of bird-plane collisions, and millions of birds die from flying into skyscrapers, communications towers and other structures," Bowlin said. "Better understanding of the altitude patterns of birds' flights could eventually help us reduce these occurrences."

Bowlin's findings have just been published in the journal The Auk: Ornithological Advances.

Hat tip Phys Org

Swainson's thrushes (

Birds in flight often arrange themselves in aerodynamically optimum positions, according to a new paper in the

journal Nature

that helps to explain how birds fly in such impressive formations. Lead researcher Steven Portugal and his colleagues focused their study on northern bald ibises, but many bird species also exhibit the amazing flight behavior. Portugal, a University of London Royal Veterinary College researcher, told Discovery News that birds could be using three things to achieve their flying precision: "(1) vision – watching the bird in flight to get all the information they need, (2) feathers – sensing the changes in pressure, wind etc. through their flight feathers, and (3) positive feedback – i.e. they just fly around and when it feels easier/better they stay in that position."

The researchers determined that birds try to find "good air," meaning airflows (not just wind, but even the air created by other flapping wings) that minimize their energy expenditure and help them to get where they plan to go. Conversely, birds avoid regions of "bad air" that could work against them.

Many birds fly in distinctive V-formations. Portugal said, "The intricate mechanisms involved in V formation flight indicate remarkable awareness and ability of birds to respond to the wing path of nearby flock-mates. Birds in V formation seem to have developed complex phasing strategies to cope with the dynamic wakes (turbulent air) produced by flapping wings."

Military planes sometimes fly in what is known as an "echelon formation," which mirrors nearly the exact same flight formation of many birds. This particular bird version is a variation of the "V," only with a rounded edge.

The U.S. Navy's famous flight demonstration squadron The Blue Angels often flies in a trademark "diamond formation" once popularized by fighter-bomber pilots. In it, the pilots maintain an 18-inch wing tip to canopy separation. Birds can fly even more tightly together.

The term "murmuration" refers to a flock of starlings. These birds can create dramatic patterns in the sky, such as this one over marshlands near Tønder, Denmark. Other small birds, such as sandpipers, may also create what look to be dazzling aerial ballets in the sky as they fly en masse.

Even birds flying very close to land can do so in remarkable unison. Here, a formation was photographed as the birds flew over the beach at Camperduin in the Netherlands.

The classic "V" formation has all sorts of variations. In this case, three separate -- yet united -- groups create an arrow-like effect in the sky.

Alfred Hitchcock's classic horror film "The Birds" included many scenes where numerous birds blanketed the sky. Up close, these starlings look small and harmless but, as a huge murmuration, their power becomes evident.

From the earliest planes to those in design today, aircraft have been modeled after birds. It's no wonder. Every inch of this sleek northern bald ibis, snapped while flying over Tuscany, adds to the bird's flying prowess. Its 53-inch wingspan and powerful, synchronized wing beats must have captivated people in the ancient world too, since ancient Egyptians and other early cultures featured the birds prominently in their artwork and legends.