148 BULLETIN 130, UNITED STATES NATIONAL MUSEUM 



Young birds probably breed the following spring and at the next 

 postnuptial molt become fully adult, when 27 or 28 months old. 



Adults have a partial prenuptial molt, involving mainly the head 

 and flanks, in March and April, and a complete molt in August. 

 There is no true eclipse plumage and no marked seasonal change. I 

 have a highly plumaged adult male in my collection, collected Octo- 

 ber 4, in which the white nuchal patch is merely indicated by a nar- 

 row, broken outline and the frontal patch by a short row of small 

 white feathers. 



Food. — The food and feeding habits of the surf scoter are prac- 

 tically the same as those of the other scoters and other diving sea 

 ducks. Their food consists almost entirely of various small mollusks, 

 such as mussels, sea clams, scallops, and small razor clams. The 

 large beds of the common black mussel which are so numerous and so 

 extensive in the tidal passages of our bays and harbors or on out- 

 lying shoals are their favorite feeding grounds. Large flocks, often 

 immense rafts, of scoters spend the winter within easy reach of such 

 beds, which they visit daily at certain stages of the tide; although 

 they can dive to considerable depths to obtain food if necessary, they 

 evidently prefer to feed at moderate or shallow depths and choose the 

 most favorable times to visit the beds which can be most easily 

 reached. Their crops are crammed full of the small shellfish, which 

 are gradually ground up with the help of small stones in their pow- 

 erful stomachs and the soft parts are digested. A small amount of 

 vegetable matter, such as eelgrass and algae, is often taken in with 

 the other food, perhaps only incidentally. Dr. F. Henry Yorke 

 (1899) says that, on the lakes of the interior, "it feeds on shellfish, 

 especially mussels, crayfish, and fish spawn; besides a few bulbs of 

 aquatic plants." 



Behavior. — The flight of the surf scoter is not quite so heavy as 

 that of the white-winged scoter; it is a smaller, lighter, and livelier 

 bird on the wing, but it so closely resembles the American scoter in 

 flight that the two can not be distinguished at any great distance. 

 It rises heavily from the surface of the water and experiences con- 

 siderable difficulty in doing so unless there is some wind, which it 

 must face in order to rise. This necessity of rising against the wind 

 is well understood by gunners, who take advantage of it to approach 

 a flock of bedded birds from the windward, forcing the birds to rise 

 toward the boat and thus come a little nearer. When once under way 

 the flight is strong, swift, and well sustained. In calm weather or in 

 light winds migrating birds fly high, but in windy or stormy 

 weather they plod along close to the waves. They often fly in large 

 flocks or irregular bunches without any attempt at regular forma- 



