La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Population trends in Baltic passerine migrants, elucidated by a combination of ringing data and point- and summer-count indices
Auteurs :	Jorgen Rabol, Auteur ; Carsten Rahbek, Auteur
Type de document :	Article
Dans :	Dansk Ornitologisk Forenings Tidsskrift (96(1) 2002)
Article en page(s) :	15-38
Langues:	Anglais
Résumé :	Large numbers of migrant passerines were ringed during spring and autumn on the small Danish island of Christianso in the Baltic Sea. For the period 1976-1996 we investigated the population trends using catches (corrected for trapping effort) of 29 species as population indices. Populations of most species remained stable; only three species showed a tendency to decline in spring or autumn, and two species to increase. Seen at a finer time scale, numbers of most species increased during the first 6-9 years, decreased during the following 10-12 years, and then increased again. The spring and autumn indices of migrants on Christianso appear to reflect the variations in the populations involved, although they correlate rather poorly with the point or summer-count indices from Sweden, Denmark, or Finland. A major cause of the poor correlation probably is that point-count indices mainly track the singing, territorial males, whereas ringing of migrants monitors both sexes and all age-classes, with some over-representation of the young population segments.

Lundi , mardi et jeudi de 9h à 12h et de 13h à 17h00 : ouverture au public ...