312 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



7 to 10, exceptionally 14 or even 17 ; greenish-stone. Average of 

 70 eggs, 58.3x41.7. Max.: 62.3x45.1. Min. : 53x41.8 and 

 53.5x39.6 mm. Breeding -season. — Usually about mid-May in 

 central Europe, but early May in Mediterranean region. Incubation . 

 — By female alone. Period 27 days (St. Quintin), 28 days (Hein- 

 roth). Single brooded. 



Food. — Mainly roots, buds and seeds of water-weeds (Potamogeton > 

 Myriophyllum, Ceratophyllum, etc.). Also small fish, tadpoles, 

 spawn, small Crustacea, and mollusca ; also water -insects. 



Distribution. — British Isles. — Very rare vagrant. Since the first 

 in July, 1818, eight or nine Norfolk, besides flocks of thirteen and 

 four Sept., 1906. A few others recorded (all autumn or winter), 

 chiefly east coast England, as follows : — Northumberland (one), 

 Yorks. (one, Jan., 1900), Lines, (two), Cambs. (two or more), Suffolk 

 (several), Essex (one), mouth of Thames (flock of eighteen), Staffs, 

 (one), Bucks, and Herts. (Tring Reservoirs, flock), Sussex (flock of 

 14-16, Jan., 1911), Hants, (one), Dorset (one), Devon (two), Corn- 

 wall (one), Pembroke (one), Westmorland (one), Argyll (three), 

 Kerry (one). 



Distribution. — Abroad.. — Mediterranean countries to central Asia, 

 exceptionally in Germany and south Hungary, wintering in Mediter- 

 ranean, south-west Asia and in India. Accidental in Baltic Pro- 

 vinces, Germany, France, Belgium, Holland, Denmark, once in 

 United States. 



Genus NYROCA Elem. 



Nyroca Fleming, Philosophy of Zool., n, p. 260 (1822— Type by 

 tautonymy Nyroca nyroca). 



Hind-toe with wide lobe of skin. Fourth (outer) toe about as 

 long as third (middle). Bill about as long as head. Culmen slightly 

 concave, bill after tip as wide as at base or slightly wider, nail less 

 wide than half of tip of bill. Edge of feathering on sides of bill 

 forming a convex line. Nostrils much nearer base than centre of 

 bill. Tail much rounded, 14 rectrices. Wings not over long, inner 

 webs of primaries more or less whitish. Sexes different. 15 species, 

 all continents and most islands. Nests on ground, females do not 

 " quack." Dive for food. 



Key to species of genus Nyroca. 



{Chest rufous .... 

 Chest black .... 

 Chest brown with white edges 

 2 f Head and neck rufous . 



\ Head and neck black 

 o /Back black and white, no crest 



\ Back black, crest 

 . / Wing-speculum grey 

 \ Wing-speculum white 



N. nyroca $ ad., p. 318 



N. ferina 6* ad., p. 313 



N. marila, $ ad., p. 325 



N. fuligula, 6* ad., p. 321 



N. ferina, ?, p. 314, 



