Birds Build Nests with Camouflage in Mind

Researchers gather the first experimental evidence that birds actively select nest-building materials that hide their nests.

Researchers have recorded the first direct evidence that birds consider the notion of camouflage when they choose colored materials for their nests.

A team from the University of St. Andrews wallpapered male zebra finch cages in different colors. Then they filmed the birds building their nests, giving them paper strip choices for nest material in two different colors.

The scientists observed that the finches largely chose paper strips for their nest that were a match with the paper covering the walls of their cages. This told them that birds will actively seek to match a nest's colors with those of its surroundings, and that what often looks like coincidental camouflage may indeed be a deliberate choice.

One interesting curve ball the finches threw at the researchers was to sometimes choose a small proportion of paper strips for their nests that was a mismatch with the wallpaper. The scientists think this means birds sometimes use a tactic called disruptive camouflage, wherein bits of clashing color break up the outline of the nest and make it look less like a bird lives there.

Prior evidence abounds for the idea that birds will move a nest elsewhere if predators lurk too close by, but the St. Andrews team asserts it has shown that birds may also try in more subtle ways to avoid predators.

"Like us (birds) don't choose just any colored material to build their homes; they avoid colors that would clash with their surroundings. Knowing this gives us a better idea of how birds may actively reduce the chances of predators finding their nests," said the report's author, Dr. Ida Bailey.

The team's work has just been published in the ornithological journal The AUK.

Scientists in the U.K. observed zebra finches making nest-building choices that took into account how well the color of materials would camouflage their homes.

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.