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Dutch Birding volume 35 (2013) no 2


Thick-billed Murre at Schiermonnikoog in October 2005

On 23 October 2005, a Thick-billed Murre Uria lomvia flew past the Wadden Sea island of Schier­monnikoog, Friesland, the Netherlands, during an exceptional mass movement of Little Auks Alle alle. The bird passed the observers at a distance of c 130 m under good observation conditions, even allowing photographs to be taken. The overlap of individual characters between Thick-billed Murre and Common Murre U aalge or Razorbill Alca torda is discussed and it is stressed that the identification of Thick-billed Murre should be based on a combination of characters. In particular, attention is paid to the spatio-temporal variation in head moult in Common Murre and Razorbill. It is concluded that Common Murres and Razorbills in head moult might very occasionally resemble Thick-billed Murre but that place and time should be taken into account (and would not apply to the Schiermonnikoog record). The apparently longer white lesser and median underwing-coverts in Razorbills compared with both murre species is highlighted, causing a larger proportion of the underside of the tertials to be concealed: two differences not mentioned in the literature. Identification of the Schiermonnikoog bird is based on the following combination of characters: structure (pot-bellied, hunch-backed and thick-necked); bill shape (too short for Common Murre, too pointed for Razorbill); head pattern (dark side of the head, well-demarcated pale throat patch and thin breast-band); upperparts coloration (jetblack); pattern of underwing (paler underwing than typical Common Murre, in particular the armpit, less white on underwing than Razorbill); and flank pattern (no streaking, white extending high upon flank). The Schiermonnikoog bird has been accepted by the Dutch rarities committee (CDNA) as the eighth record for the Netherlands and concerned the second individual to be recorded while (still) alive.

Ben Wielstra, Piet Heinstraat 31, 2231 RK Rijnsburg, Netherlands
Rob van Bemmelen, Nieuwlanderweg 28, 1793 ET De Waal, Texel, Netherlands