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June has provided us a great opportunity to talk about something that has only recently gotten much scientific attention: quiet songs/calls. I'll unpack what I know in the following thread. 1/ https://twitter.com/JH_Images/status/1350943209896243201
So in general, we can group animal vocalizations into 2 groups: long distance vocalizations, which are typically high-amplitude & often audible to the human ear & short distance vocalizations, which are characterized by their low amplitude & are often masked to the human ear. 2/
The vast, vast majority of what's known about vocal signaling in all animals, but especially birds, is focused on long-distance vocalizations, primarily those given by males. Still, at least 433 birds (and not just songbirds) in North America produce quiet calls/songs. 3/
Before we go any further let me quickly differentiate between two types of vocalizations in birds: songs and calls. Generally speaking, songs are characterized by their length, complexity, and pattern. Songs are most often used for breeding/territoriality. 4/
Calls OTOH, are shorter, simpler vocalizations and they have a much wider utility. Call types include: alarm, contact, begging, flight, assembly, etc. 5/
For a variety of reasons, scientists have paid relatively little attention to quiet sounds, but one thing we can confidently infer is that their quietness implies that the receiver is close by. That knowledge gives us some clues as to the utility of quiet sounds. 6/
And we have actually been able to determine the function of some of them. Song sparrows, for example, use quiet songs as a means of communicating to a very nearby male that they are ready to fight if their foe doesn't back down. 7/
Mate/mate or parent/offspring is another source of quiet sounds whose purpose is a bit easier to interpret. 8/
Among corvids, quiet sounds are very widespread, if not outright ubiquitous. I'd guess that a great many backyard bird feeder, even if they're not a corvid fan, has heard the whispers of blue, Steller's or scrub jays. Crows & ravens likewise make a variety of these calls too. 9/
And we see the same patterns in those birds as we do in others: quiet sounds are generally for a nearby receiver and may be uttered for mates, offspring, or during conflicts. 10/
But there's one piece of this puzzle, the one that speaks more specifically to June's video, that I have yet to resolve. What does it mean when they are, according to our best observations, completely alone and making these sounds? 11/
There's three possibilities I've seen uttered in the lit but never examined: that they are displacement behaviors (meaning an irrelevant behavior that arises in response to a conflict of urges), they're practice, or they are for fun. 12/
Watching this video reminds me so much of seeing a raven in Fairbanks do the same thing. In that case the raven was alone, appeared relaxed, & continued on for 15-20min. So if I had to guess (which I do because apparently there's no study) I'd say this raven is just having fun.
But I would love to hear from some other folks on their thoughts on the functionality of alone time whispering among corvids. Maybe @sabrinaschalz in her studies of communication has seen something I haven't? LMK! 14/14
