Eidereend Somateria mollissima eet vis

Eiders have hard-shelled molluscs and crustaceans as their main prey. Soft-bodied prey, such as polychaetes or fish eggs are sometimes taken; fish are only rarely reported as prey. A wounded, adult male Eider that had apparently been attacked by a seal, dog or bird, was brought for rehabilitation to Ecomare, Texel, in November 2011. Rehabilitation was considered impossible and the bird was euthanized and kept for later inspection. Its proventriculus contained 13 nearly undigested Sand Smelts Atherina presbyter, 7 more digested fish and two large Brown Shrimps Crangon crangon. The stomach and gut contained otoliths of 35 additional Sand Smelts. The various stages of digestion, from intact fish in the proventriculus to eroded loose otoliths in the stomach showed that this bird had taken several fish meals in succession. With the exception of the two shrimps, no other prey species were found, indicating that this Eider had at least temporarily specialised on eating fish. In total, (remains of) 55 fish were found (whole fish and otoliths only), varying in length between 4.5 and 7.7 cm, and equivalent to 87 grams of fish, or 635kJ. This compares to the basic metabolic rate of an Eider, estimated at 559 KJ d-1.