Why do birds sing?

Bill Chaisson
Of a Feather
The Merlin app is inevitably changing the way I “watch” birds. Its memory is a lot better (and bigger) than mine, for one thing. When I turn it on and hold up my phone in the woods now, all of the chips, checks, twirrs, and trills are now being assigned identities. In mid-summer the amount of singing has declined substantially, but concerned parent birds and their fledgling charges are making all manner of sounds. I, for example, know the song of the black-throated green warbler, even if I hear only part of it, but it turns out that I wasn’t at all familiar with its wheezy call.

This morning (August 1), I took the dog out for her dawn constitutional and Merlin located a chipping sparrow, a song sparrow, an indigo bunting, black-capped chickadees, house wrens, a brown creeper, a winter wren, cedar waxwings, a downy woodpecker, and American goldfinches. Only two of these—the song sparrow and indigo bunting—were singing. The rest were merely muttering or otherwise idly issuing their calls. I was standing in a meadow, so I confess that I did not even hear the distant high-pitched sounds of the creeper or winter wren. This a.m. symphony unfolded in less than five minutes.

Merlin is not, of course, flawless. It has occasionally misidentified bird calls, which I know because I was looking right at the bird when it made the sound. A particularly querulous yellowthroat was confidently called a house wren, which I found understandable, but still.

And the mimic thrushes are a bit of a problem. We were sitting by a beaver pond listening to a gray catbird when suddenly brown thrasher, eastern towhee, and veery popped up on the list. Those birds were not, in fact, present, but were apparently within this catbird’s realm of experience, and he had imitated each of them in rapid succession.

Merlin has technical limitations too, which to be honest may be limitations of my phone’s microphone rather than the software. I am unable to walk along with the phone held out and reliably have it hear any birds. Even on the softest of forest floors, the crunch of my footsteps registers as quite loud and drowns out most more distant sounds. Also, even if I am standing still but the breeze is moving the canopy around or a nearby stream is enthusiastically rushing downhill, the bird sounds do not emerge readily from the fog of white noise generated by the leaves or the water.

This latter problem could perhaps be overcome with the purchase of directional or parabolic microphone but I’m not sure I (a) want to make that investment or (b) want to carry such a thing around in the field. It is appealing to me, however, that if the external environment is quiet, Merlin can help me locate higher frequency calls and songs that are getting lost in the white noise of my tinnitus.

The app has also made me much more conscious of sound in this relatively quiet time of the year. Its ability to give names to the many calls that I’ve let slip by has led me to pay much more attention to the communications between adult and juvenile birds that are so much a part of the natural panoply from late July into early August. I have been tracking down many more juvenile birds than I usually do and have learned their parents’ concerned calls when I (inadvertently) get too close. I honestly don’t think I have ever seen a half-grown hermit thrush before.

It is also interesting to me who is still singing and who is not. Red-eyed vireos, of course, never seem to stop singing. Indigo buntings start late and keep going. The hermit thrush is still understandably singing, as it does have a reason to defend a territory: it is guarding a foraging area so that it can continue to feed its voracious progeny. I occasionally hear a yellowthroat or a black-throated green warbler sing, but I haven’t heard a black-throated blue or a yellow-rumped warbler sing in at least two weeks.

Birds sing for many reasons. The most well known reasons are (a) to attract a mate and (b) to defend a territory. This time of year the “attract a mate” reason is definitely in the rear-view mirror. And some of the species that have stopped singing have perhaps finished rearing this year’s brood(s) and therefore no longer need to defend a patch of Earth.

“True” songbirds learn to sing by listening to their elders. Even the most casual birdwatcher quickly notices the complexity of some bird song. As most people would intuitively suspect, the more complicated songs must be learned or, more specifically, refined from a sort of rough draft that is genetically transmitted. However, the so-called “critical period” during which songbirds do this learning occurs while they are still in the nest. Although it is possible that some very late nesters—like goldfinches—might still have nestlings, it seems unlikely the adult singers I hear now are giving singing lessons.

This learning ability explains why birds have regional dialects. For example, I was struck by the song of the ovenbirds in this part of New Hampshire. It is very much a CHER-tee, CHER-tee instead of the TEE-cher, TEE-cher I am used to and that I heard in upstate New York in June. Oregon song sparrows also had a quite different repertoire, although I couldn’t possibly describe the differences in words.

One of the strengths of the Merlin app is that it includes all these regional dialects. You can download the library for a particular region of the U.S. or the entire continent. Furthermore, if you plan to travel, Cornell has libraries for most countries throughout the world.

I put off downloading and using Merlin because I thought of it as “cheating.” But that was silly. It is, in fact, a great learning tool.

Bill Chaisson has been a birdwatcher for 50 years. He lives and works in Wilmot.