Is there anything more fresh than walking through the cool morning air at, or just before, sunrise, hearing the morning chorus of birdsong? I confess it has been too many years since I have done so. This evening, though, taking a walk near dusk, I was treated to an evening chorus no less sweet or varied. There is a patch of woods near home, between one neighborhood and the next, as is the fashion in Eastern suburbs. It has been pretty well left alone since this development was built up some fifty years ago. This patch partly abuts a schoolyard, so we have our choice of a grassy sward or a running track to walk on.
I've noticed the birds and their singing in the past, but tonight I had different ears, all from reading Birdsong: A Natural History, by Don Stap. Perhaps half of the book is composed of information about singing birds and some history of the study of songbirds and birdsong. The structure of the book, though, is a picaresque history of the career of Don Kroodsma. The author has been privileged to accompany Dr. Kroodsma on a number of expeditions and excursions to record birdsong and study singing birds.
The recording itself is one thing. Making something useful of it is quite another. For that, one uses a sonograph, or sonic spectograph. Here is an example of the resulting sonogram.
The vertical dimension is frequency, with higher notes at the top. The scale ranges from 2,000 to 9,000 Hertz (1 Hertz = 1 cycle per second), for few bird sounds are outside this range. 9,000 Hz is an octave or two higher than most people can whistle. That's why it is hard to reproduce a bird's song. This song begins with a high chirp, a short beat of silence, then a lower whistle, followed by four chirps in the medium frequency range. To hear the sound and see & hear a few other examples, check out this Audubon Society site, which promotes Don Kroodsma's recent book The Singing Life of Birds. I've bought the book and will review it soon.
The song shown is called "Song A" because there are several dialects of the Eastern Towhee. Much work over the past twenty to thirty years has been done to record birds that have, and those that don't have, dialects, and to attempt to understand the differences.
Dr. Stap's writing recalled to me my early love of hearing birds sing. As a preteen with a new tape recorder, one of the first things I did was put the microphone outside my second-storey bedroom window and record a half hour or so of the birds waking up at daybreak. Now, 42 years later, if I can ever find that tape, it will be a valuable record. Birdsong begins with a description of the Macaulay Library of Natural Sounds. Many, many of the sounds record birdsong, including many dialects and variations.
It takes a great many recordings to produce a comprehensive collection of birdsong. Not only are there many singing birds—nearly all the passerines (perching birds), more than 5,500 species out of 10,000 or more total bird species—but some birds sing numerous different songs. Most (maybe, maybe less than most) have two calls, a territorial song and an alarm call. Many have a few or a few dozen songs, and there are some birds that sing hundreds or thousands of different songs. Some, such as the chipping sparrow, occasionally engage in repertoire contests, with a number of tiny birds, "dueling banjos" style, singing song after song to one another, very rapidly, often in a fixed order, in which the duelers either match one another note for note, or each jumps ahead to the next song, then the next...on through as many as four thousand songs.
Rather than grow this post to an hour's reading, I'll leave the rest for those who are interested, to check out or purchase Don Stap's quite enjoyable book.
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