88 BULLETIN 130, UNITED STATES NATIONAL MUSEUM 



when the food supply is only a few fathoms below the surface; they 

 often dive to depths of 6 or 8 fathoms and sometimes 10 fathoms, 

 but when forced by the rising tide to too great exertion in diving, 

 they move off to some other feeding ground or rest and play until 

 tiie tide favors them again. They are usually very regular in their 

 feeding habits, resorting to certain ledges every day at certain stages 

 of the tides, as long as the food supply lasts. They seem to prefer 

 to feed by daylight and to roost on some inaccessible rock to sleep 

 at night. Many other ducks are forced to feed at night, as they are 

 constantly disturbed on their feeding grounds during the day; but 

 the eider's feeding grounds are so rough and inaccessible that they 

 are seldom disturbed. Even in rough weather these tough and 

 hardy birds may be seen feeding about the ledges white with 

 breakers; they are so strong and so expert in riding the waves and 

 in dodging the breakers that they do not seem to care how rough 

 it is. I have seen them feeding, off our eastern coasts in winter, 

 in water so rough that no boat could approach them. 



Their favorite food seems to be the common black mussel {Mytelis 

 edulis), which grows in such extensive beds as to furnish abundant 

 food for myriads of sea fowl ; the eiders devour these in such large 

 quantities that their crops are most uncomfortably distended. Peri- 

 winkles, limpets, and a great variety of other univalve and bivalve 

 mollusks are eaten; their stomachs are crammed full of such hard- 

 shelled food, mixed with pebbles, all of which is ground up by the 

 strong muscular action of the stomach, assisted by the chemical 

 action of the gastric juices; the soft parts are digested and the pul- 

 verized shells pass out through the intestines. They are said to 

 eat small fish occasionally, as well as fish roe and that of crustaceans. 

 Starfish, sea urchins, and crabs are eaten, even the great spider 

 crab and other large crabs measuring 2 inches across the carapace. 

 Mr. Millais (1913) says: 



I remember once, in Orkney, running clown to a flock of feeding eiders that 

 for the moment had vanished beneath the waves. One rose near the boat 

 with something like a thick stick projecting 5 or 6 inches from its mouth, 

 which it was unable to close. I shot the bird, an old female, and found that 

 the obstruction, when drawn out, was a razor shell {Ensis siliqua), 10 inches 

 long and 3 inches in circumference. How any bird, even with the digestion 

 of a sea duck, could assimilate so tough a morsel with a hard and thick shell 

 seemed a marvel, but it is doubtless the case that they are able to break them 

 up and eject the shells as pellets. 



Kumlien (1879) writes: 



Their food in autumn consists almost entirely of mollusks. I have taken 

 shells from the oesophagus more than 2 inches in length ; from a single bird I 

 have taken out 43 shells, varying from one-sixteenth to 2 inches in length. 



