The cuckoo bird is considered a parasite because it has a nasty habit of laying its eggs in other bird's nests, and the runaway parents have developed a few tricks to prevent egg rejection from their suspicious foster parents.
The cuckoo often lays more than one egg in the nest of their victim, the African tawny-flanked prinia. This technique makes it harder for the prinia to distinguish between the imposter's eggs and their own, and lowers the rate of egg rejection, a University of Exeter press release reported.
Cuckoo eggs look strikingly similar to those of the prinia, which makes it extremely difficult for the birds complete the "sensory task" of telling the two apart.
In order to tell which egg is which the prinia must look very carefully at miniscule differences between pattern and color. It's also important that the bird's don't make a mistake, or else they risk throwing their own eggs out of the nest.
"This is a cognitive task relying on an ability to process the sensory information and compare it to a [memorized] template of what their own eggs look like," the press release stated.
Having two parasitic eggs in the nest causes the prinia to confuse which patterns are their own and which belong to the cuckoo.
"Our work shows that by laying multiple eggs in each host nest, the cuckoo finch has evolved a novel strategy, in addition to egg mimicry, to defeat host [defenses] and increase its reproductive success. Laying several eggs in a host nest causes confusion in host [defenses], and when combined with effective mimicry, they can outwit the hosts and help more of their young to be reared," Dr. Martin Stevens from Biosciences at the University of Exeter, said.
"In the future it would be great to know whether other brood parasites have similar strategies, and whether there is any way that hosts can fight back in the arms race against the cuckoo finch," he said.
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