Seabirds at sea, June – August 1991

MV Navicula sailed to, from, and around Helgoland 29 May-5 June (MFL, HO). Guillemots were numerous around Helgoland. Concentrations of Common Scoters near Texel (3300) and off Terschelling (36,000). Migrating Brent were seen regularly in the German Bight. On its survey in the eastern half of the North Sea (IJmuiden-Skagen), 3-12 June, MV Tridens II was manned (CJC). During this cruise, being part of the International Bottom Trawl Survey, the German Bight and Danish waters were well studied. The only species occurring in numbers was the Fulmar. Interesting were mass-feedings of Fulmars, up to 5000 individuals together, picking small particals (probably zooplankton) from the surface. High densities were also encountered in places in the German Bight and off Noord-Holland. Coloured specimens were seen quite frequently (though <1%). Auks were extremely rare. Gannets, Kittiwakes, and Larus-gulls were seen frequently, but in very small numbers. June’s aerial survey was delayed well into July due to bad weather technical improvements which were being made on the plane. It is now equipped with a GPS navigation system, probably the most precise position indicater to date. On July 3rd the coastal flight (for routes and details see Sula 5: 16-23) again proved to be useful for mapping foraging gulls and terns. North of the Waddensea islands several groups of scoters were found, totaling up to 13,600 Common Scoters and 200 Velvet Scoters. Hardly any birds with male plumage were seen in any of the groups. This could mean that they were largely non-breeding subadult birds spending the summer on the Dutch coast. Fair weather on July 8 and 9 enabled us to survey the Dutch sector of the Continental Shelf (DCS) further offshore with the Texelflight on 8th and the Borkumflight on 9th. On both flights few birds were seen once we got further offshore which is normal for this season, with only 2 Great Skuas, few Gannets, Fulmars and Kittiwakes and low numbers of Herring Gulls and Lesser Black-backed Gulls. Only 20 large auks (Guillemot or Razorbill) were seen. A Great Northern Diver in winter plumage seen 30 nm west of Europort may have been a summering immature bird (HB).