Sunday, May 13, 2012

Bird Song, Borror, Thoreau, and Traveling in Place


I used to think birds of the same species were genetically programmed to sing the same song. And so when I began listening carefully to bird song, I was surprised to find slight variations. I assumed these were accidental, the result of a bird's genetic defects or my inexperience in listening. Curious, I began reading what the ornithologists had to say about it. It turns out that, on the contrary, some young male birds must "learn" their species song from their elders. And very occasionally one does not get it quite right--and when that happens, the offspring may learn that slightly different melody.

Today on my walk in the woods, after three days of heavy rain, I heard a bird singing three of the five notes of the black-throated green warbler's song--the first, second, and fourth only. I concluded that it must be a youngster learning his song. Within a half-mile radius, a couple of other adult birds of that same species were singing all five, so it won't be long before this youngster likely has it right.

But one of the consequences of birds having to learn their songs is that songs of the same species may vary a bit, according to geographical region. The black-throated green warbler's five-note song on this island in East Penobscot Bay, where I spend time when not teaching at Brown or traveling, is typical for Maine. But black-throated green warblers who take up their spring and summer residences outside this region of northern New England sometimes feature a four-note song--that is, only four of the five heard around here. And some have a six-note song, even here.

Novice bird watchers often have difficulty recognizing songbirds by sight--they are small, shy, and do not care to be close to humans. Moving targets, they are not easy to bring up close with binoculars until the novice has practiced with them. In the spring and summer when they are singing, mating, and nest-building they are easier to recognize by sound than sight. Besides, anyone with an interest in the soundscape will pay attention to bird song.

About fifteen years ago I made tape recordings of bird songs on the island where I spend time when not teaching at Brown or traveling. In hopes of identifying them, I compared my recordings to the standard ones on CDs from the Audubon Society and other authoritative sources. But some of the identifications were difficult or impossible, due, I realized, to differences in regional bird song dialects.

To proceed, I needed to find recordings of the birdsong dialects I was hearing. After some searching, I found that Donald Borror (1907-1988), of the Ohio State University, made the recordings that most closely matched the bird songs I was hearing in Maine, and for an obvious reason: he recorded them in Maine. (A brief and informative biography of this bioacoustics pioneer may be found at http://elibrary.unm.edu/sora/Auk/v106n02/p0321-p0323.pdf). 

Borror used a top-of-the-line Nagra reel to reel tape machine with a very sensitive microphone inside of a parabolic cone. (He was also a pioneer in recording techniques.) As a result, his recordings are technically excellent even by today's digital standards. Some of his recordings were issued on LPs in the 1960s, with his commentary aimed at bird watchers interested in identifying birds and bird behavior by sounds. Dover Publications reissued them as cassettes, in the early 1970s, with lengthy accompanying booklets. Borror understood about song dialects and on these recordings aimed at the general public he was careful to say where he made each recording. Today, thousands of Borror's recordings are available for listening on the Ohio State website at http://drc.ohiolink.edu/handle/2374.OX/30658 but this huge database is useful primarily for the scientist and advanced birder wanting to compare songs from the same species according to geographic area and over a forty-year time period. There are, for example, more than fifty separate recordings in the database for the black-throated green warbler. 

Interestingly, Borror also released an LP (Bird Song and Bird Behavior), later reissued by Dover on cassette, which took up various topics of interest to anyone curious about bird song, including how to make recordings of bird songs (and the problems in doing so), classifying bird sounds, types of songs, singing habits, song development in a particular bird, geographic variation in songs, duet singing, differences between songs and calls, making sound spectrograms of bird songs, and so forth. Borror's biographer, his colleague Sandra Gaunt, wrote that he "was a private and retiring person. He preferred to spend his time in the field collecting or in the laboratory organizing, analyzing, and describing his collection." 

Like Thoreau, Borror observed natural sounds by returning seasonally to the very same locations, year after year. Like a bird, Borror migrated annually from southern Ohio to the state of Maine, recording in both places. Gaunt writes, "I once asked Borror if he did not wish that he had traveled more broadly in his years of collecting. He allowed that his participation in the Pacific Theater [in World War II] was all the world travel he cared to experience and, more seriously, that there was more than enough to document at home." Emerson criticized Thoreau for staying close to his home in Concord, Massachusetts most of his life. Thoreau fashioned his reply: "I have traveled much in Concord." Indeed, Thoreau walked every afternoon (and on moonlit nights) to observe the changes in the natural world and, occasionally, his neighbors. Ecologists, of course, study small area ecosystems intensively today. Gaunt concluded, "For many of [Borror's] locations he obtained recordings of many species for nearly 40 consecutive years. These repeated samples supported the research effort of one man, and today they are a valuable, if not unique, resource for future studies, especially studies of song pattern variation in time." 

Bird song presents an interesting contrast with music; that is, with music as humanly organized sound. We have no problem calling bird vocalizations "song" even though they do not meet the scientific criteria for music. Nor do they meet the criteria for language, because they lack language's recursive qualities. Music composers throughout history and in many different cultures have been inspired by the melodies of bird song, sometimes directly imitating it, and sometimes transforming it. One ethnomusicologist, Steve Feld, wrote a book about the complex cultural ramifications of the belief, among the Kaluli people of Papua New Guinea, that bird song is a signal from departed ancestors.

What are the songs of birds telling us about sound and communication, the uses of sound as signal (territory, mood, danger, location, etc.)? What do they tell us about sound and place, about sound and movement, about the ecology of the acoustic niche? And finally, what can we learn from birds about music, sound, and sustainability? Thoreau and Borror both were struck by the seasonal, the calendrical, the cyclical repetitions of bird song and sound in the natural world. Thoreau's last great (and unfinished) project was his cyclical "Kalendar" of the seasonally changing natural world around Concord; his journal observations were made to that end, as were Borror's recordings--longitudinal studies, intensively rather than extensively, of sound and sustainability, by traveling in place.

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