The scientists figured out the parasite bird's egg trick

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North American bullheads are typical rogue parents. Like more than 90 other birds, they throw their eggs in the nests of other birds, leaving the task of caring for young birds to other birds. This has led to an arms race in which defrauded adoptive parents have evolved ways to fight back, while deceptive bull-headed birds have evolved countermeasures. Now, researchers have found that spots on a bird's egg play a key role in parents' decision to keep it or "kick it out" of their nest.
the most common victims of glittering bullheads is the grey-eyed bird. The bird's eggs are blue-green and speckled, while the bull's-headed eggs are pure white and brown, and also have spots. The researchers hypothesized that the bird would reject a bovine egg of a different shape and color than its own. But new research has found that things are not that simple.
To better understand how birds deal with these eggs, Daniel Hanley, an evolutionary ecologist at Long Island University in Brookville, N.Y., and colleagues painted 70 3D-printed eggs in various colors and painted spots on half of them. They distributed the eggs to the nests of 85 better birds and checked a few days later how many more eggs remained in the nests.
the results show that spots are often the basis for a bird to judge whether an egg is different, even if its color is "incorrect." Hanley and colleagues report the findings in the April issue of the Royal Society B Philosophical Journal.
researchers found that 90 percent of the time, the bird cleans up the spot-spot-less brown egg, which has the "wrong" color and pattern. But if there are spots on the eggs, the birds are less confident. They remove spotted brown eggs only 60 percent of the time. Generally speaking, more birds are more acceptable to blue eggs, even those that are bluer than their own. And when these blue eggs have spots on them, parents keep them for more than 90 percent of the time.
" adds spots to make an egg more acceptable. Sheena Cotter, an evolutionary ecologist at the University of Lincoln in the UK who was not involved in the study, said. Spots are therefore an easy way for parasitic cattle-headed birds to ensure the safety of their eggs, even if their matching is not perfect.
sometimes, this defiant bird does more than just make sure the egg has spots. In Zambia, Mary Caswell Stoddard, an evolutionary biologist at Princeton University, and her colleagues recorded 122 eagle eggs removed from their nests. The researchers noted the color, size, and marking of each egg in each nest and used sophisticated pattern recognition computer programs to classify the shape and orientation of the markers.
when an alien egg is very similar to its own, the eagle uses the shape and position of the speckle to make the right judgment. Stoddard and colleagues report the findings in the same issue of the Royal Society B Philosophical Journal. "The exact location of a point is hard to imitate." Cotter points out that this allows the eagle to use this information when it is not possible to determine whether an egg belongs to itself.
Rose Thorogood, an evolutionary ecologist at the University of Helsinki in Finland who was not involved in the study, said the two papers solve a long-standing problem of how parasitic birds recognize the difference between their eggs and impostor eggs.
new research shows that sometimes adoptive parents are very alert and picky about the eggs in their nests, added Stoddard. When parasitic birds evolved spots as part of the egg camouflage, adoptive parents evolved more brain power so that they could remember more details about the spots and become more discerning.
"What happens in the brains of birds is more complex and interesting than we think. Stoddard said. (Source: Zhao Xixi, China Science Journal)
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