Dutch Birding volume 34 (2012) no 5

Sooty Tern at Maasvlakte in August 2012

On 31 August 2012 at c 09:00, an adult Sooty Tern Onychoprion fuscatus was seen and photographed by a single observer at Maasmond, Maasvlakte, Zuid-Holland, the Netherlands. The bird was seen flying west (out to sea) at c 300 m distance for c 30 sec, and six useful photographs were obtained. The bird was described as similar in size to Sandwich Tern Sterna sandvicensis. The very dark upperparts limited the identification to Bridled Tern O anaethetus or Sooty. The identification as Sooty was based on the following characters: 1 size: Sooty is almost as large as Sandwich, Bridled is visibly smaller; 2 colour of upperparts and upperwing: blackish to black in Sooty (often with brownish wash in first-year or worn adult birds), dark grey in Bridled (with black primaries); 3 head pattern: large white forehead patch with weak loral line seemingly connected to white on underside of head and not extending beyond the eye in Sooty, smaller patch extending as white supercilium beyond the eye and more prominent loral stripe in Bridled; and 4 underwing pattern: more contrasting with solidly dark (outer) primaries in Sooty, slightly less contrasting with wingtip more gradually darkening towards tip in Bridled. In addition, the tail does not look very long, which also fits Sooty better than Bridled. The brownish tinge of upperparts and the lack of a distinct black loral line may indicate an immature but the photographs show too little detail of the head pattern to establish the exact pattern and a brownish tinge also occurs in worn adults.

If accepted, this is the first record for the Netherlands; the species is a rare vagrant in the Western Palearctic, almost exclusively in the summer months. Most records in Europe are from Britain and France.

Ben van den Broek, Degerfors 3, 3123 EJ Schiedam, Nederland
(benvandegmail.com)
Enno B Ebels, Joseph Haydnlaan 4, 3533 AE Utrecht, Nederland
(ebelswxs.nl)