A parasitic cuckoo can be a good thing
In moments of danger, intruder chick releases slime that may foil attackers
MIXED BLESSING A great spotted cuckoo chick (front) doesn’t directly kill the carrion crow nestlings it grows up with and, in a crisis, it may benefit the entire nest.
Courtesy of Vittorio Baglione
A parasitic cuckoo chick foisted upon other birds can turn out to be luck in disguise, saving the nest with a disgusting defense.
About 1 percent of bird species, including cuckoos, outsource their childcare by sneaking into other birds’ nests and leaving an egg.
The intruder chick often kills or outcompetes the rightful offspring of a nest. Defense by cuckoo chicks of carrion crow nests at high risk of predator attack could be the first example of a parasitic bird’s benefit to its host, says ecologist Daniela Canestrari of the University of Oviedo in Mieres, Spain.
Chicks of the great spotted cuckoo (Clamator glandarius) don’t directly kill chicks of the carrion crows (Corvus corone corone), so the crow parents have a chance of producing some of their own offspring. When lots of predators lurk about, the cuckoo chick’s strong defense mechanism — emptying its bowels of a caustic, stinking slime — may explain why
