Bird Song (and other Sounds)

By Roger Grimshaw

A light broke in upon my brain

It was the carol of a bird.

Byron The Prisoner of Chillon

Man has long been fascinated by living creatures, and there is a long history of appreciation of birds for their beautiful plumage, their bright joie de vivre, and their song. In fact song and birds are inextricably linked, celebrated by poets and composers the world over. Certainly, other groups of animals sing (whales, crickets and some monkeys, for example), but for most of us none of them can compete with birds for the loveliness of their song. Song is surely linked in our minds with birds, as much as their ability to fly and their possession of feathers.

Singing is most characteristic of birds in the order passeriformes, this group comprising about 5000 of the worlds 9000 or so bird species. The oscine passerines include most of our familiar small birds, from crows to cardinals and including warblers, sparrows and Carolina wrens. Some non-passerines sing, including hummingbirds, but their songs are generally less developed and attractive (to our ears, at least).

Birds sing for two main reasons :

1. To attract a mate and

2. To establish and hold a territory.

As might be expected from these functions, singing is mostly a male activity. Under the influence of a seasonal increase in hormones, the male is ready to breed. To raise a family, he first needs to establish a home or territory. Most larger animals defend a territory, a certain area which the individual claims for his own use (and that of his family) and from which he excludes all other individuals of his species. When a male sings, he is laying claim to his territory and sending a message to other males "this is my property, keep out". The territory may be an acre or less, or several square miles depending on the species. The bird may be able to establish and maintain his territory by song alone. If another male tries to invade his territory, he is likely to respond with increasingly vigorous song, display flight, or if necessary physical confrontation. However, song often enables the bird to repel its rival without physical contact.

Once the bird has established its territory, it needs to find a mate. Once again - for many species - song is the key. The song used to attract females may be different from the one used to establish a territory. If the bird successfully attracts a mate, and once eggs are laid, he may reduce the frequency of the female attracting song, but still keep up the territorial song. He must keep the food and cover on his territory for himself and his family.

Birds produce sounds in various ways. Not considered further here are sounds made by knocking on trees (woodpeckers) and noises made by wind passing through feathers (e.g. nighthawks and snipe), although they may serve a similar function to song in other species.

The avian equivalent of the mammals larynx is the syrinx, a hollow structure situated where the trachea splits to form the two bronchi. This location on the two bronchi enables the bird to produce different sounds from each bronchus simultaneously (or to breathe through one while singing with the other!), and makes possible a very complex song. The name Syrinx will be familiar to classical scholars, Syrinx was a nymph who was pursued by the god Pan. Running to escape his embrace, she was cornered when her way was blocked by a stream. By her wish, and to escape her pursuer, she was transformed to a hollow-stemmed reed. When the wind blew over the opening, a soft musical sound was produced. Pan tied several of these reeds together, and thereby invented the pipes that bear his name.

Singing is a potentially a risky business to a bird. The song that attracts a wife, can also attract a predator! Even a bird like a painted bunting, which usually stays well hidden in dense cover, can often be easily seen when perched high and singing. To the bird it is worth the risk. Breeding is the only chance he has to transfer his DNA to a new generation.

It has been shown that there are advantages and disadvantages to different song characteristics. For example, low frequency (pitch) sounds travel further (in part by reflection from the ground), but require more energy to produce, and may not be anatomically possible for small birds. Higher frequency sounds are more easily distorted by vegetation, but are common in birds which live in open areas. Many birds sing from the top of a tree to enhance sound propagation. Some open country birds sing while in flight to gain extra height.

As you might expect, song is most noticeable in the breeding period (roughly February to July here in Central Florida). We often hear the first northern parula song around Valentines Day, and then increasing amounts from various birds up to the peak around the end of May. However there is some singing all year round (especially this far south). You will also notice some wintering birds singing, I have noticed this in American robins later in the winter. You can buy recordings of bird sounds to help you learn their songs.

Hopefully, when our birds start their breeding cycle this spring you will be able to enjoy their song with a bit more understanding of what is going on, and why. Instead of throwing the alarm clock at that wren, youll react more like Sir Joseph Banks, naturalist with James Cook, who, while at anchor off the coast of New Zealand in 1770, wrote "This morn I was awakd by the singing of birds...their voices were the most melodious wild musick I have ever heard, almost imitating small bells...".

 

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