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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.
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Moller used a play-back technique to investigate the effects of singing by the black wheatear (Oenanthe leucura) on the behaviour of both conspecifics and heterospecifics. It was found that singing increased in both groups in response to the wheateater and Moller suggested the dawn (and dusk) chorus of bird song may be augmented by social facilitation due to the singing of conspecifics as well as heterospecifics.
In some territories where bird life is extensive and birds are vocal, the sound of a dawn chorus can render early morning sleeping difficult.
International Dawn Chorus Day
An annual International Dawn Chorus Day is held on the first Sunday in May where the public are encouraged to rise early to listen to bird song, at organised events. The first ever was held at Moseley Bog in Birmingham, England in 1984, by the Urban Wildlife Trust (now The Wildlife Trust for Birmingham and the Black Country).
New Zealand
Early explorers and European settlers noted that the New Zealand forest had a loud dawn chorus. This is no longer the case due to extensive loss of forests and the introduction of bird predators and competing species such as wasps. The bellbird and the tui are two of the birds that would have formed part of the dawn chorus since they have a vocal and melodious call.
United Kingdom
In the UK the dawn chorus may begin as early as 3am in early summer. The most often heard species of birds are, in order of them beginning to sing:
In non-avian species
Several primate species vocalise early in the morning as an audible territorial display. These include the lesula (Cercopithecus lomamiensis), the black howler (Alouatta caraya) (which can be heard 5 km away) and the mantled guereza (Colobus guereza).