BLACK DUCK 169 



with olive or brownish feet and olive bill; more difference in size between 

 sexes than in the Red-leg. RED-LEGGED BLACK DUCK: Larger 

 bird, with a yellowish bill and coral-red feet; more rugged and with 

 heavier feathering; more prominent white tipping to feathers of the 

 greater coverts, which feature is either entirely lacking or very much less 

 evident in the Common Black; females more nearly the size of males 

 than in the Common Black. 



The differences in habits and behaviour claimed to exist between 

 the two Blacks are: COMMON BLACK DUCK: (a) Earlier migrant, 

 with a more southerly breeding range, (b) migrates as early as mid-Sep- 

 tember, or at least shifts from breeding grounds to better feeding 

 grounds, (c) less shy, (d) decoys more readily to live decoys, (e) more 

 loquacious, (f) less nocturnal in feeding habits, (g) on the coasts in winter 

 less inclined to spend the day on open ocean, (h) prefers fresh and 

 brackish water food, (i) feeds in both fresh water ponds and salt 

 meadows. RED-LEGGED BLACK DUCK: (a) Late migrant, with a 

 more northerly breeding range, (b) shows greater resistance to cold 

 weather, (c) more wary, (d) more silent, (e) seldom decoys even to live 

 decoys, (f) when flocks do decoy, they alight at a safe distance and ap- 

 proach very cautiously with necks erect, and keep less closely together 

 than Common Blacks, (g) on the coasts in winter more frequently sit 

 offshore in rough seas, (h) seldom resorts to small ponds, but chooses 

 the larger sheets of open water near the ocean to which it resorts to 

 drink but not to feed, (i) prefers marine food. 



ARGUMENT AGAINST 



On the other hand, many prominent ornithologists and some sports- 

 men maintain that the Black Duck should not be divided into two sub- 

 species for the following reasons: 



(a) The differences which exist between the two forms are exactly 

 those which distinguish old birds from young, (b) They point to the 

 case of the closely related Mallard of which two kinds are recognized: 

 the later migrant, a larger bird, heavier feathered and having orange 

 coloured feet and yellow bill, and the earlier migrant, a smaller bird, 

 with red feet and darker bill. It is conceded that the later migrant is 

 merely the older bird, better fed and more fully recovered from the effect 

 of the summer eclipse moult. From this parallel it is inferred that the 

 same holds good in the case of the Blacks, (c) They point to many 

 other instances among the ducks where young birds habitually migrate 

 earlier than the old. (d) On the question of the darker feet and bill of 

 one variety it is claimed that all juvenile Blacks have dark feet, includ- 

 ing those from points farthest north which are supposed to lie within the 

 breeding range of the Red-leg; and that all adults after the breeding 

 season and during the eclipse moult also assume the duller colour of feet 

 and bill, which parts progressively become more vivid in colour coinci- 

 dent with the development of the full plumage late in the autumn, 



