A mid-August walk finds the woods almost silent. A raven talks, a jay complains, an eagle titters, a squirrel chatters. If you are lucky, a little group of chickadees will come by and visit. But bird song is over for the year. Warblers are on the move, singly and in small groups, ready to spend the winter down south.
Why should the absence of bird-song make me think about singing? Maybe when the spring chorus is in full swing, I’m too busy listening, but now I have time to notice the emptiness.
It has long been known that male birds sing to attract mates and advertise their nesting territories. Songbirds commonly learn at least part of their breeding season songs by listening to their fathers’ songs and perhaps also those of their neighbors. In some cases, localized dialects develop, in which all the males sing very similar songs and females tend to prefer males that sing the local version. This is apparently more likely in birds that are year-round residents; examples are heard in the songs of white-crowned sparrows along the west coast. Sometimes song learning in migrants also occurs on the wintering grounds where populations can mix and hear each others’ songs as they warm up for the spring season. And some birds, such as mockingbirds and starlings, readily mimic the songs of other species.
Something different has happened with the white-throated sparrow, which nests all across northern North America. Its characteristic song consists of two notes followed by three triplets, rendered in English in the U. S. as “Old Sam Peabody, Peabody, Peabody. Over a decade ago, however, a change was noted in the song of males in western Canada (where the song is said to say “O sweet Canada, Canada, Canada”). But those western males weren’t singing the triplets anymore; they were now singing duplets instead. And, strangely, this new version of the song spread gradually eastward, to Quebec (as of 2020). No one really knows why the new song is taking over; one suggestion is just that the females like the novelty of it, which raises the question of what the next novelty might be!
In other cases, changing conditions may cause birds to change their songs so as to be heard more clearly by each other. Several studies have shown than birds in cities sing at a higher pitch than their country relatives, perhaps to be heard over the background cacophony of city noises, many of which have low pitches. Social context also matters: birds tend to sing longer and faster songs in areas where their populations are denser and there are more potential territory intruders.
Many studies have shown that singing has huge effects on emotional, mental, and even physical well-being of humans. Those of us who have enjoyed choral singing with local groups know well some of those benefits. More recently, research has found that birds probably get similar benefits. Now it seems that, in addition to attracting mates and advertising territories, they may also sing for the pure pleasure of it, as Darwin once suggested.
Starlings gather in large flocks when the nesting season is over. In those flocks, both males and females sing a lot—not the songs of the breeding season, but more unstructured, less ritualized songs. In studies with captive starlings, researchers had found that, given a choice, the birds preferred to be in aviaries where they had previously participated in group singing—perhaps because it was pleasurable. Then the researchers experimentally manipulated the levels of the birds’ natural opioids; opioids are the chemicals that induce feelings of well-being and pleasure and they also reduce pain. Their production can be stimulated by certain conditions, such as being in a safe place with friends, and activities, such as eating and singing. So we—and birds too, perhaps–feel good when those things happen. And feeling good may, in turn, favor more associations with safe places and more eating and singing.
The researchers demonstrated that, using drugs, they could stimulate the production of natural opioids by the body and trigger lots of group singing, simultaneously reducing stress-related behaviors. Conversely, when the production of natural opioids was experimentally reduced, group singing was also reduced…and the birds no longer preferred to be where they had experienced group singing before. There may be more to the emotional life of birds than we give them credit for!