“How Does a Cowbird Learn To Be a Cowbird? New Research Explains How These Brood Parasites—Who Are Raised by Other Species—Still Manage to Become Cowbirds”, 2016-02-25 (; backlinks):
…In laboratory experiments, cowbirds and other brood parasites that spend too much time with their foster families end up learning their host species’ songs, picking up their behaviors, and attempting to mate with them. In the wild, though, they’re somehow able to resist this—by the time they’re about a month old, they’ve learned to act like cowbirds, and they know to mate with their own species. The more Louder looked into the question of how they do it, though, the more he realized we really don’t know. “It’s kind of bothered people for a long time”, he says.
…To test that idea, the researchers attached radio transmitters to adult cowbirds and their young. The data revealed that the juveniles didn’t follow older birds away from the nests and rarely ventured to their mothers’ homes. Instead, they go on nighttime rendezvous.
“They seemed to, just one night out of the blue when they were about 20–25 days old, say ‘Oh man, I need to go somewhere’”, Louder says. “It’s almost like zugunruhe, or migratory restlessness.”
The data showed that young cowbirds leave the host nests shortly after sundown and roost overnight in the fields where the species typically lives before returning to their foster families the next day.
“When I saw them do it, I was just shocked. You’re gonna leave in the middle of the night to go somewhere you’ve never been?” Louder says. “To me, it just seems that would be the most dangerous time to do this, and that’s what led us to believe that it’s extremely important.”
The team thinks these night flights—which may be spurred by an innate preference for roosting in fields—give the cowbirds some independence from their foster parents and keeps them from becoming something they’re not. Since adult cowbirds roost together at night in the same fields, the young birds’ excursions could also give them the opportunity to mingle with their own species and learn the right behaviors.
…“These guys are really cool. They have these crazy behaviors and what they’re doing is really complex”, he says. “If this was easy, everybody would do it.”