Are Egg Shells a Sun Screen for Birds?
Birds in flight often arrange themselves in aerodynamically optimum positions, according to a new paper in thejournal 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."
H.K. Job, Wikimedia Commons
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.
Rupert Ganzer, Flicker
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.
Daniel Jolivet, Flickr
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.
Mark Kent, Flickr
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.
It seems birds know a thing or two about sun screen, using just the right SPF number on their egg shells to protect their embryos.
A new University of London study published in the journal Functional Ecology suggests that birds use adaptations in both color and shell thickness to let the perfect amount of sun light reach their youngins' inside the egg.
The research team used the museum eggs of 75 bird species to measure how much light could penetrate the egg for a given species.
They found that egg shells got the right amount light they "needed," based upon their exposure to ultraviolet rays. For example, the eggs from birds that nest in holes or deep cavities had very white shells that let in as much light as possible. By contrast, they found, birds that nest out in open areas with more direct sun exposure use extra pigment so the sun light can be dialed back.
Duration of exposure mattered too, the team learned. Birds with long incubation periods need thicker shells and more pigment for protection, so that's what they have adapted for themselves.
"Embryos do need UV exposure to develop. Too little and they don't develop enough ... too much and it causes damage," team member Dr. Steven Portugal told BBC Nature. Luckily for the birds, they're well aware of the danger and seem to have tailored their eggs to moderate it.