La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Why does the Song Thrush Turdus philomelos furnish its nestcup with a smooth lining?
Auteurs :	Josef H. Reichholf, Auteur
Type de document :	Article
Dans :	Ornithologischer Anzeiger (42(3) Oktober 2003)
Article en page(s) :	235-242
Résumé :	The Song Thrush normally provides its nest cup with a smooth lining of wood pulp and mud or dung, but the function of this time and energy consuming activity is obviously not known. Contrary to some earlier results concerning the insulating properties of the Song Thrush nests compared with that of Blackbirds, the effects described are in fact not only much too slight to explain such sophisticated behaviour but also no thermal function is derived from them. But older publications on the amount of botfly larvae Protocalliphora sp. and the more destructive nestfly maggots of Neottiophilum praeustum indicate another explanation, i.e. the firm and smooth lining makes the nest unsuitable for the fly larvae. The high losses of Song Thrush nests under construction or containing eggs can be compensated, therefore, to some degree by a better survival of the nestlings before leaving the nest. In accordance with these conclusions Song Thrushes show a better fledgling rate than Blackbirds and a greater variance in population fluctuations from year to year. The function of the smooth lining of the Song Thrush nests, therefore, is the enhancement of nestling survival by creating unsuitable conditions for dangerous fly parasites in the nest.

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