Stacey Cole's Nature Talks: Bird songs, calls are their 'primary means of communication'
STACEY COLE |
May 31. 2013 8:18PM
Birds have been singing and voicing other calls for a few weeks now. Recently, the Hon. Alice Calvert of Alton, former legislative friend and column reader, requested an answer to the question: "Why do birds sing?"
Bird songs and their calls are a bird's primary means of communication. In late spring and early summer, males sing for two basic purposes: First, to attract a mate, and second, to let other birds know that the singer is announcing its claim on a particular territory. This is a warning to others to keep out! If a male believes his warning is being ignored, in defense, he frequently will "dive-bomb" the intruder by flying as close to it as possible. If that alert proves to be ineffective, his next attack will be to vigorously strike the offender. Such attacks often will end with a battle on the ground. Beating wings and pecking beaks can prove fatal at times. Throughout the years, I have witnessed several such knock-down ground fights. Such a battle can result as an ugly sight!
Generally speaking, I have found that recognizing bird songs is most helpful in bird identification. Knowledge of the sounds they make can be especially helpful when heavy foliage has arrived to make it easier for birds to conceal themselves. Actually, bird sounds are used in bird identification in more instances than one might think.
Knowledge of bird calls, chirps and songs are utilized throughout the year. For example, during Christmas bird counts that begin at midnight, owls are listed by species when each distinctive hoot or call is heard. Also, in conducting a breeding bird survey, singing males are used to indicate the territory of a nesting pair.
In the preface to his book, "A Guide To Bird Songs," published by Doubleday & Co., Inc., in 1951, Aretas A. Saunders wrote: "Every kind of bird has its own call or song. It says its name for the benefit of the bird student. If we can train our ears to know and remember the difference between species, we have a way of identifying birds under circumstances when they cannot be seen clearly enough to be identified by sight."
In my early years while attending Vermont Academy, my biology teacher, Mark Emerson, and I would take "bird walks." During those strolls he encouraged me to learn as many of their songs and calls as I could. He pointed out individual birds and commented on their songs before identifying them.
One might think that all birds of the same species sing exactly the same song, but Mr. Emerson taught me that was not always the case. It's more accurate to say that each bird of the same species really sings its individual song. Another male's song may sound similar, but it can contain subtle differences of tone and expression that makes each bird unique. It is a rarity, however, when the same species of a bird's individual song is so far off the norm that its species is unrecognizable.
My experience has been that greater success in identifying an individual song has more to do with the ability to distinguish the differences of rhythm than of sound. While some observers believe that every bird species appears to follow its own law of rhythmic time, no matter how the song may sound from birds of the same species, others disagree. For example, Maurice Thompson, in his "Sylvian Secrets" wrote: "There is no such element as the rhythmic beat in any bird-song that I have ever heard. Modulation and the fine shades of 'color' as the music critic has it, together with melodious phrasing take the place of rhythm. ..." Rhythm or not, I love to listen to the songs of birds.
In 1941, the sound spectrograph was invented at the Bell Laboratory resulting in sonar being used effectively during World War II. In 1945 this technology was released for public purposes. In the late '50s sonagrams began to be utilized as a basis of bird song identification. And it is sonagrams and their interpretation that are the key to a bird song book published by Houghton Mifflin. Written by Donald Kroodsma, "The Singing Life of Birds" is designed to "open the eyes and ears to the world of birdsong."
Sonagrams are picture voiceprints that plot a sound's frequency over time, revealing tone, rhythm, change and diversity involved in a bird's song. They appear as mostly vertical lines of various lengths and widths, occasionally horizontally joined or separated. Looking at them I was reminded of making charcoal line drawings, smudged in places to emphasize highlights and shadows.
"The Singing Life of Birds" also includes a compact disc of 98 recorded tracks of bird songs. A special section describes each numbered track so that one can select a track and easily follow the sonagram as it progresses. This, I found, was a most fascinating exercise.
Stacey Cole's address is 529 W. Swanzey Road, Swanzey.