Bibliothèque Tour du Valat

Se connecter

Mot de passe oublié ?
Pas encore inscrit ?

La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Détail

Ajouter au panier

Ajouter au panier

Lien vers la notice

Titre :	American Black Duck Anas rubripes and Mallard A. platyrhynchos abundance, occurrence of heterospecific pairing and wetland use between 1976 and 2003 in Northeastern Nova Scotia, Canada
Auteurs :	Norman R. Seymour, Auteur ; Sean C. Mitchell, Auteur
Type de document :	Article
Dans :	Wildfowl (56 2006)
Article en page(s) :	79-93
Langues:	Anglais
Résumé :	Mallard Anas platyrhynchos abundance has increased in eastern North America with a concomitant decline in the number of Black Duck A. rubripes in some parts of their range. It has been speculated that introgressive hybridisation or competitive exclusion have been the mechanisms for the opposing population trajectories of these species. In particular, the prevailing view is that heterospecific pairs of male Mallard x female Black Duck are contributing to the hybridisation of the two species, with a combination of Mallard releases and use of urban areas increasing the frequency of these pairings. This paper reports long-term survey data documenting the relative frequency and combination of sexes of mixed pairs from two sites in eastern Canada, and the extent of movement of Mallard into habitat dominated by Black Duck from points of Mallard concentration in Nova Scotia. This study indicates no long-term decline in Black Duck, nor an increase in Mallard, in northeastern Nova Scotia between 1976 and 2003. Heterospecific pairs in Nova Scotia were rare and consisted primarily of male Black Duck x female Mallard; heterospecific pairings were more common in a St. Lawrence River study area and were mainly of the expected male Mallard x female Black Duck combination. Two clines with respect to heterospecific pairing are suggested from these data: (1) an increase in frequency, and (2) a change in male : female composition by species moving from east to west. The occurrence of Mallard appears to be limited to a 1-km to 3-km radius from discrete points of introduction or concentration. Within this radius, Black Duck abundance was low. Outside this area, at a 3-km to 15-km radius, it then increased twofold at Shubenacadie and sevenfold at Goshen. Thus, Mallard releases in this area appear to have only localised effects. This study found no evidence for Mallard or hybrid increases, Black Duck declines, the occurrence of competitive exclusion, or of introgressive hybridisation in Black Duck in northeastern Nova Scotia between 1976 and 2003.

FAQ

Infos pratiques

Heures d'ouverture et contact

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

Liens utiles

A-
A
A+