One of the great joys of spring in Maine is hearing the song of a newly arrived White-throated Sparrow. It’s distinctive poor–sam–peabody–peabody -peabody (or as our northern neighbors prefer, my–sweet–Canada–Canada–Canada) evokes the Maine woods. We are treated to this song all summer long.
I had to grin when I recently heard a song that sounded vaguely like a White-throated Sparrow but with a certain hesitancy and missed notes. What I was hearing was a young male, born just a few months ago, learning to sing.
About 60% of birds belong to a single order, the perching birds, or passerines. That order is split into two major groups: the songbirds or oscines, and the suboscines. The songbirds include virtuosos like thrushes, Ruby-crowned Kinglets, warblers, sparrows, orioles, and many others. In Maine, flycatchers are the only suboscines we have. There is far more suboscine diversity in the tropics. But all suboscine males sing very simple songs. Think of the fee-bee of the Eastern Phoebe, the che-bek of the Least Flycatcher or the sneezy fitz-bew of a Willow Flycatcher.
The songs of suboscines are innate. No learning is required for an Alder Flycatcher to sing its fee-bee-o song. The ability of a suboscine to sing its specific song is encoded in its genes. In contrast, in at least 31 families of songbirds, males (and females in those species in which females sing) must be tutored.
Young songbird males raised in isolation do not learn to sing their species’ characteristic song properly. They will sing but it is hardly recognizable to us. Certainly, females of that species will not be enticed to size up such a male and consider mating with the song-challenged male.
Song learning in songbirds is a huge area of research and we know much about the process. Researchers have identified distinctive stages in song learning. The first, called the early critical period, begins in the nest, and continues for at least several weeks. The brain of the young bird is receptive to the songs of adult males. In most cases, the tutor is the dad of the young bird but not always. For example, Bewick’s Wrens in the western United States first learn their father’s song but then modify it by learning the songs of neighboring adults when it begins to nest.
This period is an important window. A bird isolated for the first part of its life and then exposed to adult song after the early critical period will not be able to learn songs. It will still sing but the song is rudimentary.
The next stage is called the silent period. During this time, the songs heard in the early critical period are fixed in the brain of the bird.
Then, the young bird advances to the subsong stage. The song I recently heard was an example of subsong. The bird was doing its best to recreate the song it had learned and fixed in its brain earlier. This stage is quite like babbling in human babies. Sounds are being tested. Some ornithologists refer to these song attempts as whisper song because of the low volume of the sounds.
The final stage is the plastic song stage. Having developed some facility with singing the proper notes and phrases, the bird achieves the ability to sing an honest-to-goodness rendition of the song of its species. As any musician knows, practice makes perfect.
The bird I heard was clearly in the subsong stage. He may return next year to lift my spirits with a full-throated, poor-sam-peabody-peabody-peabody song.
You may wonder why songbirds don’t learn the songs of other species of birds in the area. Ornithologists have identified an innate auditory template in birds. This template is genetically inherited and provides a bird with the ability to recognize the sounds of its own species and filter out the songs of other birds and frogs as well as sounds like waterfalls and ATVs.