6o 
British Diving Ducks 
the place of the shells of these, probably for the purpose of digestion, and it is so effectual that even 
mussel shells are so extraordinarily ground down that it is got rid of as though it were coarse sand. 
"The edible mussel {Mytihis edulis) seems to be preferred by them to all other species, and 
they swallow specimens of these which are as long as 3.5 cm. Their gullets often seem stuffed full 
of these, and places at which they can find mussel banks of this species at the bottom of the sea 
are the favourite haunts of this duck. They bring them up from the bottom of the sea at a depth 
of some fathoms, and are continually diving under for them, and busy themselves with this so often 
and for so long, apparently at the same place, and until they are scared away or leave the spot, that 
one marvels at their insatiable appetite, but probably it is the search and choosing of suitable specimens 
of these which helps to account for this. 
Birds have been fed in captivity on soaked bread, and kept alive for some time." 
An interesting piece of information from Gatke, loc. cit., proves that they sometimes 
also enjoy vegetable food : 
"A ship went aground and broke up one stormy winter night on the long southern point of 
the dunes near Heligoland, with a cargo of the smaller grey horse-beans, and the whole cargo was 
carried eastward by the current and scattered over the bottom of the sea. This undoubtedly quite 
new dish to the Common Scoter was so much appreciated by them that soon thousands of them 
had collected at the spot, and dallied for over a month at the place which offered them this obviously 
favourite food at a depth of some 10 fathoms in ample sufficiency. All the specimens which were 
obtained at that spot were literally clothed in fat, which, unlike their normal condition, was very 
white and well flavoured. These birds possess no trace of the fishy taste which clings particularly 
to adult males." 
F. S. Mitchell notes that cockles (Cardium edule) and other sand mollusca are eaten, 
and T. E. Gunn has found remains of small bivalves. Mr. G. Bolam has found chiefly 
Sandhoppers [Gammaridce), with an occasional shrimp, and quantities of sand. 
In the breeding season they must subsist almost entirely on fresh-water mollusca 
(F. C. R. Jourdain). 
The adult Common Scoters begin to migrate northwards about the end of March. 
In Denmark and North Holland they do not move much before the middle or end of 
April, whilst numbers often delay until May before they take their departure. The 
majority of the immatures also go northwards, but whether they go to the sea coasts 
near the breeding grounds or not I cannot ascertain, for no naturalist seems to have 
made observation of this point. I saw no flock of immatures in Iceland either on the 
coast or on the inland waters in summer, but under any circumstances these might 
easily have been overlooked, as the Common Scoter is only a somewhat scarce breeder 
in that island. As we have already pointed out, numbers of Scoters, both adult and 
immature, stay throughout the year on the winter resorts and do not migrate north- 
wards. Common Scoters that have spent the winter on the N. Danish coasts generally 
leave at the end of March, but birds that have wintered in the south-west arrive at 
the end of April in North Denmark, and follow the earlier birds at once throughout 
late April and early May. 
As a rule the breeding birds on the Sutherland and Caithness lochs do not arrive 
until the end of May, and this is also the case in N. Iceland. Naumann speaks of seeing 
them starting on their northern migration as late as June 13, but I think that although he saw 
large numbers of Scoters at the mouth of the Elbe at this date, it does not necessarily 
follow that these birds were migrating at all. They might only be performing a short 
