Tuesday, 11 September 2012

Autumn song

Robin in song (c. John Fox)

Autumn bird song is very unusual amongst our garden birds, with a notable exception.. Most birds sing from late winter / early spring, in order to establish a territory, attract a mate and then nest and raise young in the territory.

Robins sing in autumn, once the moult is completed.   Their sweet, controlled song is all the better to listen to with no competing song from Thrushes and Blackbirds to distract the listener. 

 The function of autumn song is presumably to establish an autumn or feeding territory.  However, the feisty defence of the feeding territory occurs at a time of plenty for food resources.  Ironically, Robins will suspend their aggression in hard weather when other birds will share what food is available before starting up singing in early spring, in advance of the breeding season. 

David Lack, a pioneer of Robin studies, writing in the classic, Life of the Robin,(1943), offered the idea that the occurrence of autumn song was a signal of the birds intention to stay the winter rather than migrate, as many other birds do at this time.  Robins do of course undertake movements: from high to low ground in winter.  The continental race of our Robin does migrate on a more regular basis and influxes of continental Robins have been noted on islands such as Cape Clear in October, leading to much territoriality from the population of indignant residents!

Robin (c. R. Martin)

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