Diet of Sandwich Terns Sterna sandvicensis on Juist (Germany)

In the southern North Sea, Sandwich Terns Sterna sandvicensis typically occur at the border between the Wadden Sea and the open sea (Camphuysen & Leopold 1994, Garthe el al. 1995). On a large scale, this species is therefore considered to be an 'inshore' species (Garthe 1997). At a smaller scale, however, its distribution differs substantially from the other tem species being more orientated towards the sea and occurring in much lower densities close to the mainland coast (Garthe el al. 1995, unpubl. data). Although 8000-9000 pairs breed along the German North Sea coast – the highest population size this century (Südbeck & Hälterlein 1997) only one study has focused to some extent on the diet of Sandwich Terns (Gorke 1990). We therefore investigate in this paper the diet at a well-accessible colony in the German Bight. This colony was established in 1994 with 700 pairs (Halterlein & Sudbeck 1996). Colony size increased in subsequent years: 1071 pairs in 1995 (Sudbeck & Halterlein 1997), 2370 pairs in 1996 and 1460 pairs in 1997 (P. Sudbeck pers. comm.).