La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	[Population size and breeding biology of Night Heron Nycticorax nycticorax in the Danube valley of eastern Bavaria]
Auteurs :	Franz Leibl, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (122(2) 2001)
Article en page(s) :	95-99
Résumé :	From 1981 to 1995, Black-crowned Night Herons bred only at a single location in the Danube valley of eastern Bavaria. The population varied between 2 and 7 breeding pairs. After damming of the river near Straubing, two more colonies were founded in 1996. The population rose to a maximum of 30 pairs in 1999. One factor in the population increase was the availability of safe breeding sites (willow growth on islands in the river). The breeding biology of Night Herons was studied in detail in 1998 und 1999. The earliest eggs were noticed on 2 May. Normally nestlings fledge by the end of July. Only in 1999 breeding lasted into August, because a period of flooding in June led to brood initiation of additional pairs after others had already started breeding. The average number of fledged young per initiated clutch was 2.28, successfull breeding pairs raised an average of 2.7 young (n=32). The success rate of breeding attempts rose from 56% during the period 1984-1990 to 85% during the 1990s. However, the slow die-off of flooded willows serving as nesting trees makes it uncertain for how long this population will persist.

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