Why Do We Have a Dawn Chorus?
The song of the birds at dawn has given pleasure to millions of people and has been celebrated in poetry and prose for many years. The most usual explanation given in the Middle Ages was that the birds sang each day in praise of god and the beauty with which He had clothed the world.
More recently, there was the feeling that the birds sang joyously to welcome the rising of the sun, which meant food, warmth and activity. However, scientists now think that the dawn chorus is made up to the warning signals of each bird as he re-establishes his territory.
The establishment of a territory for courtship, nesting and food getting is the first step in the breeding cycle and the area is defended against competing birds of the same species by a warning song, although seldom by actual fighting. A robin, incidentally, has a particularly strong sense of territory.
The dawn chorus occurs when birds sing at the start of a new day. In temperate countries this is most noticeable in spring when the birds are either defending a breeding territory, trying to attract a mate, or calling in the flock. In a given location, it is common for different species to do their dawn singing at different times.
In a study of the Ecuadoran forest, it was determined that birds perching higher in the trees and birds with larger eyes tend to pipe up first. These correlations may be caused by the fact that both would also correlate with the amount of light perceived by the bird. In some territories where bird life is extensive and birds are vocal, the sound of a dawn chorus can render early morning sleeping difficult.
To the untrained human ear, the singing may be a cacophony of sounds. But, to an ornithologist or another bird, the choral explosion is a harmony of music that is much more than the rise, fall and rhythm of notes and an amazing repertoire of joyous individual songs to welcome another sunrise.
The chorus dies down as the sun starts rising because the birds, both male and female, begin moving around to forage. That doesn’t mean the singing stops, but the purpose of the singing changes from a territorial purpose to courtship and becomes less vigorous than it was at dawn.