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Aves, 41/3-4 | 2004 | 121-134

  The Goosander (Mergus merganser) in Wallonia and Brussels Region: yesterday a scarse winter bird, tomorrow a breeding bird ?
Bronne, L.

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Article summary

From the middle of the 20th century -and probably already from the middle of the 19th centurytill 1985, Goosanders were present each winter in Wallonia or Brussels Region in very small numbers. Only hard winters sent more birds, mainly on River Meuse. From 1985 onwards the number of wintering Goosanders has considerably increased (see Fig. 1 and 2). Following the influxes of 1986 and 1987, a wintering habit was born on the lakes between the Sambre and the Meuse rivers (Barrages de l'Eau d'Heure, Roly and Virelles). 42% to 60% of Goosanders wintering in Wallonia and Brussels Region stayed in this area in mid January until the next influxes occurred in 1996 and 1997. These influxes sent birds in the areas east of River Meuse and thus created a new wintering habit on River Ourthe and its tributary River Amblève. For the first time in Belgium the species became a regular wintering bird in the grayling zone. The areas east of River Meuse (mainly Ourthe and Amblève rivers) are now the main areas occupied by wintering Goosanders. The little influx of 2003 may also have had an impact as a new area for wintering of Goosanders has been found in the southernmost part of Belgium. The summer observations of Goosanders in Wallonia since 1966 are given (Fig. 4 and 5). They become increasingly frequent and the ratio between males and females appears to be the same as in winter. The breeding range of the Goosander is known to be included between 10°C and 20°C July isotherms. Nevertheless breeding does not occur in parts of the area between these isotherms. This non-breeding area is where Europe is most densely populated (see Fig. 6). We suggest that Goosanders were eliminated by man from this area and give some non-exhaustive clues and proofs that breeding occurred in France in the 16th and 17th centuries. Since Goosander legal protection became effective in western European countries, not only wintering populations but also their breeding range are increasing. We cannot exclude that a breeding case would occur soon in Wallonia. Two isolated breeding cases have already been discovered less than 100 km from the Walloon borders.

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