74 British Diving Ducks 
like other ducks, but when in large companies they generally hold together in a solid 
phalanx, or in one long unbroken line massed in several places. 
By nature Scaup are somewhat unsuspicious and very gregarious. In their winter 
homes they keep strictly apart, and are not found associating with other species. Even 
single birds on migration will keep apart from other ducks, although they may temporarily 
find themselves in their company. 
At other seasons, except the breeding time, Scaup are very silent birds, their only call, 
generally uttered by the female, being a deep " Karr-karr-karr." A wounded male will 
also utter the same note. 
In the winter months Scaup feed little on vegetable food, unless they are regularly 
frequenting freshwater lakes. On the sea I have never seen them touch the soft roots of 
Zostera marina, so dearly loved by the Wigeon and Brent Geese, although they eat the 
seeds freely. Even in summer they only live partly on the ripe and unripe seeds of float- 
ing or submerged water plants, for in the contents of the stomachs of Scaup at this season 
are always found quantities of water insects and small fish. Their principal food is small 
shell-fish of all kinds. On the Baltic they seem to live exclusively on small single-shelled 
animals {Littorina littored). Thompson [Birds of Ireland, iii. p. 139) found in the contents 
of their stomachs single-shelled mussels such as Littorina littorea, Littorina retusa, lacnna 
quadrifasciata, rissa ulvce, cerithium reticulatum, and nassa maculata, also pieces of the 
bivalve 7tucula margaritacea, the remains of Crustacea and the seeds of Zostera marina. I 
have noticed that in very cold weather Scaup seem to prefer to frequent estuaries rather 
than the open sea, where food seems more difficult to obtain at such times. In Iceland,, 
during the breeding season. Scaup eat quantities of flies of various kinds, young trout, and 
the small freshwater snails, as well as the succulent growths of several water plants I could 
not determine. 
The majority of Scaup that have wintered in Britain leave us early in March, before 
pairing commences. Various authors have thought it necessary to record the fact that they 
have seen individual Scaup in Germany and Britain in the summer months, but any field 
naturalist who has travelled much in the summer in Scotland and the northern islands is 
certain to see one or more Scaup frequenting lakes that have been their winter home, and 
I have seen many Scaup in summer, both in Orkney and Shetland, in the months of May, 
June, and July. In some cases these birds were paired, but more often they were single. 
It is no unusual thing to find a single or pair of any sea diving ducks "out of season," 
and I have a note to the effect that I have shot a Velvet Scoter in Orkney in every month 
of the year. 
Faber and Thienemann have stated that Scaup arrive in March on the southern coast 
of Iceland, and that they work north gradually to the freshwater streams and lakes of 
Myvatn, 250 miles north, in April, and this was confirmed by natives living in Iceland. As 
soon as they arrive in big flocks on the great Lake of Myvatn, they split up into smaller 
parties and at once commence their courtship. 
The mating show of the male Scaup is not very demonstrative, and is as a rule only 
commenced by the attentions asked for by the female. In fact it seems that in ducks, as 
in most birds, the sexual desire is only fairly aroused in the male when some female has 
made repeated advances so as to arouse his passions. One female being in better condition 
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