How do crows develop such distinct and individual “voices”? I don’t hear this with other bird species in my garden.
Nicola Clayton and Francesca Cornero, University of Cambridge, and Valerie Dufour and Killian Martin, French National Centre for Scientific Research
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When you hear crows and other members of the corvid family, such as rooks, ravens, jays and magpies, you may notice that each bird has its own individually distinct voice. This is the case for many songbirds, but we find it easier to hear in crows because of how human hearing works.
We are better at detecting differences between low-pitched sounds than high-pitched ones, and crows produce loud vocalisations of much lower pitch than most birds. This means we can more easily recognise individual crows than individual robins, blue tits or blackbirds.
Scientific studies show that adult corvids have huge variation in their voices. Using artificial intelligence, we that rooks not only have individually distinct voices, but that each male has its own repertoire of calls that are distinct from those of other males.
By analogy, imagine everyone you knew spoke your language, but used a completely different vocabulary. Unlike most species, rook song isn’t tied to territoriality or courtship: rook songs seem to allow them to play, to improvise with their own voices, sometimes for minutes at a time. And they use any sound they can produce, with no discernible pattern other than to portray their acoustic distinctiveness.
Individually distinctive voices are especially important for social species where multiple individuals can live together for extended periods and may need to tell each other apart. In corvids, rooks and jackdaws form huge colonies during the breeding season and for nightly roosts, while crows, ravens and Eurasian jays are more territorial, often living alone or in breeding pairs. Distinctive voices might be more essential for the more social species than the less social ones, but work is in progress to investigate the impact of sociality on vocal individuality.
Most birds learn one or more songs early in life from their parents and other members of their species, then produce them throughout their adulthood with little modification. We have no data on how corvids acquire their vocalisations, but they may have an easier time developing individual voices because they have a rare ability for animals: they can imitate environmental sounds, including human speech.
Even in adulthood, corvids can still incorporate new sounds into their vocalisations, which could help them form their own individual signature. Ultimately, however, we know very little about corvids’ vocal agility.
David Kroop
West Friendship, Maryland, US
About a year ago, I decided to make friends with the local crows. After some coaxing, I got them to come to a feeder I built on my deck. Whenever I put out food and used a distinctive call I devised, they would come.
Their typical caw-caw sounds are more for alerting others about an event, such as when one sees me putting out food. But they also have a rather distinctive “speech”, as I discovered one time. A single crow landed on a nearby branch, looking at me on the deck, and proceeded to “talk” to me for 5 minutes. The sounds were more subtle and varied in intonation and length. The “sentences” were a series of these sounds, but each was slightly different. It looked at me the whole time it talked. That particular crow was slightly smaller (I believe her to be female), and I see her all the time. She has a mate and they tend to feed together, taking turns eating.
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