Here’s another breakthrough in avian cognitive studies: two European teams purport to show that crows and pigeons can tell individual humans apart—the crows by voice, the pigeons by face.
The crow research, led by Anna Wilkinson at the University of Lincoln in the UK, should not be all that surprising, given what we already know about the mental capacities of the corvid family. Wilkinson’s team worked with carrion crows, midsized corvids similar in appearance and behavior to the American crow. The scientists reported that the birds reacted differently to familiar and unfamiliar human voices, and to the calls of familiar and unfamiliar jackdaws (another European crow relative.) Oddly, they responded more to unfamiliar humans and to familiar jackdaws.
This appears to be the first evidence of discrimination between individual vocalizations of other species by birds, but it’s well known that corvids recognize individual human faces. John Marzluff at the University of Washington demonstrated that American crows remember people who have invaded their nests to weigh, measure, and band their chicks, and harass them without mercy. This was true even when the bander wore a caveman mask. Marzluff’s crows also somehow communicated to their cohorts that these were not nice folks; the banders were persecuted by birds in a different part of the university campus whose nests had not been molested.
It’s not just corvids. Gulls, often considered somewhat thick, also recognize and retaliate against individual humans. A few years ago I interviewed biologists who had worked with western gulls on the Farallons and Alcatraz. “The late Larry Spear figured out the gulls on Southeast Farallon recognize people by their faces as individuals,” Russell Bradley of PRBO Conservation Science told me. “He dressed up in different clothes, raingear, and a Nixon mask, and counted the number of times he was attacked when disguised. He was convinced they recognized him as an individual.” Ray Pierrotti, an Alcatraz veteran, concurred: “They recognize individuals even within a small group of people. I handled the chicks while my wife and research partner Cynthia Annett collected data. Almost all their aggression was directed at me.”
Such recognition skills could be adaptive in a number of ways. Social creatures, including corvids and primates, interact with
many conspecifics. It would pay to be able to remember who’s a reliable ally, who’s a sneakthief, who did what to whom when. Predators have to be able to read the vulnerabilities of prey, picking out the weak or sick members of the herd. Conversely, prey species may benefit from recognizing individual predators.
The pigeon study, on which Wilkinson collaborated with scientists at the University of Vienna, is the real shocker. Pigeons that had been trained to discriminate between photographs of familiar and unfamiliar objects were able to distinguish between familiar and unfamiliar human faces. Naïve pigeons were not. Pigeons, as far as I know, don’t have complex social lives; this skill set seems excessive to their requirements.
I don’t know whether Wilkinson was involved in earlier pigeon research, in which the birds demonstrated that they could tell a Picasso from a Monet. (Could they distinguish between “Guernica” and “The Old Guitarist?”)
Then again, if paper wasps, as claimed in another recent study, see other paper wasps as unique individuals, all bets are off. I’ve looked closely at the gallery of wasp faces in the July National Geographic. Peas in a pod. Not to another wasp, though.