Comox Valley Naturalists Society

April, 2003
Frank Hovenden

As the days lengthen it is often difficult to ignore the chorus of bird song that greet the coming of light to our neighbourhoods. For some this amounts to “Will that darn robin ever shut up”. For others, enjoyment of birds and their song are inextricably linked, to be celebrated both by music lovers and naturalists alike.

Why do birds sing and how do they do it? Singing is most prevalent in the order of birds known as the passeriformes and more specially in the sub-order oscines, commonly known as the songbirds.
Humans have a larynx, which produces sound when air is forced over it. In birds the equivalent organ is known as a syrinx. It is located further down the windpipe where it has two branches. This allows birds to make two separate sounds at the same time. It is also far more efficient that the human equivalent. The human larynx uses only 2% of the air which passes over it while a bird make use of nearly all the air which passes over it. This is why a little bird has a great big voice.

The vocalisations that birds make can be divided into calls and songs. Calls are generally short and are innate rather than learned. Examples are alarm calls, which may alert all other birds to the presence of a danger such as a predator. Another example of a call would be the vocalisations known as contact calls. These let other members of a flock keep in touch. Listen to the constant calls between a group of chickadees or kinglets as they travel though treetops. This calls helps to keep the flock together without any bird getting lost.

Bird songs, unlike the calls, are well-developed vocalisations that must be learned. It is generally the male of the species that sings for two somewhat related reasons. He sings to attract a mate, and to establish his territory in order to keep the mating completion away.

When the male sings he is putting up a fence of sound around his turf telling other males to keep out. If another male shows up, the singing may increase in intensity and duration. Rival males are often sent packing without any physical contact but by merely being out-sung. What a civilised way to settle a territorial dispute!

With its territory established, a bird now must get down to the business of finding a mate. It again turns to song. The song may be similar or entirely different from the one used to establish territory. Males of most songbird species have several songs in their repertoires. It is thought that females may judge a potential mate by the size and the complexity of his repertoire. Thus a young bird with a small repertoire may be passed up for an older more experienced singer.

Learning to recognize bird sounds is literally like learning a new language. It take practise and just when you think you are getting somewhere, the birds depart and the skies are silent for another a year. To add to the difficulty, birds have distinct dialects. The late Doug Innes, a local birder, spent many years studying the vocalisations of the Townsend’s warbler, a colourful little bird found in our conifer forests. He found many dialects among the populations on Vancouver Island. The birds on Denman Island sang quite differently from those in the Sayward forest.

Learning to recognize the bird songs can be difficult. Remember, you see more birds when you know what to listen for, so don’t get discouraged. There are some excellent bird sound CD’s around to help in bird recognition. John Neville, a naturalist from Saltspring Island, has made several CD’s for the various regions of British Columbia including the Coast. These are readily available and highly recommended.

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