Aves, p�le ornithologique de Natagora

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Aves, 39/2 | 2002 | 105-113

  Fidelity to the wintering site of a leucistic Black-headed Gull (Larus ridibundus) in the Meuse valley around Liège
Bronne, L., Deloyer, P. & Jacob, J.-P.

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Article summary

A Black-headed Gull which totally lacks black pigments (eumelanines) was discovered in Visé (Liège) on December 8th 1990. Since then (and until end of 2003), this bird was seen each winter at the same place (within a radius of 150 m around the Haccourt bridge). Only few sightings were made at other places, including one in Oost-Maarland, the main roosting site for gulls of the Basse-Meuse. Further observations indicate thaht this bird is apparently normal except for its lack of black pigments. The moult of its head feathers perfectly follows the moult scheme of Black-headed Gulls wintering in the same area. The behaviour of the bird with respect to its congeners shows nothing special and its presence at the wintering site takes place at an usual time compared to other gulls. As the first sightings were of a bird with no brownish feathers, one can assume that the bird was already at least in its second year. It is thus at least 15 years old. Known cases of chromatic anomalies of Black-headed Gulls in Belgium are reviewed. In addition to the Basse-Meuse bird only four cases clearly implicate a lack of eumelanines, only one in addition to a lack of pheomelanines. This is a small number compared to the tens of thousands of Black-headed Gulls seen each winter in the Walloon and Brussels regions.

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Mouette rieuse
Chroicocephalus ridibundus

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