252 THE DIVING DUCKS 



Gregarious, and sometimes seen in hundreds: visits inland as well as coastal 

 waters in considerable numbers. [A. L. T.] 



4. Nest and Eggs. The normal nesting-site of this species differs widely 

 from those of the other diving ducks, for it is usually found breeding in a hole of 

 a tree in its natural condition. In Lapland and Finland boxes are put up by the 

 peasants hi order to induce it to breed, and are often occupied. Some of the holes 

 used are formed by natural decay, others are old holes of the great black wood- 

 pecker, and the height from the ground varies considerably. No nesting material 

 is introduced by the duck except a plentiful supply of the beautiful light pearly 

 greyish white down with white feathers (Brit. Birds, ii., pi. 2, fig. 14). The 

 feathers are on an average rather smaller than those of Barrow's goldeneye, 

 which they otherwise resemble (P. F. Bunyard). There is some reason to 

 believe that at the northern limit of its range it occasionally breeds in holes 

 among rocks, like the Icelandic Barrow's goldeneye. Any Icelandic breeding 

 specimens must necessarily nest in this way, as there are no trees of any size 

 there. The eggs vary from 8 to 14 in number as a rule, but nests with 15 and 

 16 and even 19 have been recorded. When fresh they are a beautiful bright 

 blue-green in colour, which, however, soon fades. The shell is stout and has 

 little gloss, and the average size of 130 eggs is 2-33 x 1-67 in. [59-2 x 42-5 mm.]. 

 Incubation is performed by the female alone, and eggs placed under a hen 

 were hatched out in 20 days (F. E. Blaauw). Naumann gives the period as 

 22 days, but his remarks can hardly apply to this species, as he describes 

 it as nesting in the open in clumps of sedge and rushes ! In Germany full 

 clutches have been found as early as the middle of April, but in Lapland usually 

 from the end of May to the latter part of June and even later when the eggs 

 have been taken. Only one brood is reared in the season. [F. c. B. J.] 



5. Food. During the winter months the food of this species consists to a 

 great extent of molluscs and small crustaceans, as well as some vegetable matter. 

 When on salt water, mussels and other marine Mollusca, small Crustacea, especially 

 of the genera Palcemon and Crangon (shrimps, prawns, etc.), and sea grass, which 

 is brought to the surface after diving and devoured at leisure, are the chief articles 

 of diet. Other species of algae, as well as Zostera, are eaten at times. When visiting 

 fresh water and during the breeding season, fresh-water molluscs are eaten, also 

 fresh-water crustaceans such as Gammarus pulex (Jackel), tadpoles and small frogs, 

 small fish not exceeding two niches in length, and the larvae of various aquatic 

 insects, especially Cokoptera, Phryganece, and also Libettulce (Dragon-flies), as well 



