200 BRITISH BIRDS. 



many as 13 and 14 eggs, and reared two broods in the season 

 (see Ann. Scot. Nat. Hist., 1892, p. 219).— F. C. R. J.] 



DIMORPHISM IN YOUNG TERNS. 



In his notes on Terns (supra, p. 169) Mr. H. W. Robinson 

 remarked on the dimorphism exhibited by the downy young 

 of the Common Tern. Some time ago my brother called my 

 attention to the possibility of this, but no opportunity has 

 since occurred to either of us to investigate the point, so that 

 I was glad to see Mr. Robinson's observations, though it 

 would be of greater value if he could give us a more detailed 

 description of the two forms. During the last nesting 

 season, however, I was able to make an examination of a 

 large number of young Arctic Terns (Sterna macrura) up to 

 the age of four or five days, and I was not surprised therefore 

 to find that they were also dimorphic. In the light form 

 the general body-colour was a creamy white, in some almost 

 quite white, with a touch of rufous on the forehead. The 

 back was marked with spots and indistinct lines of black, 

 and there was a black band across the upper throat and 

 chin ; breast and upper part of belly, white with a wash of 

 pale slate- colour on the flanks and vent. In the dark form 

 the lower parts and all the black markings Mere the same, 

 but the general colour of the upper parts was brownish or 

 rufous white, the rusty tint being most marked on the 

 shoulders and humerus ; this varied in intensity a good deal 

 in different examples and in a few was almost absent, but 

 the two forms were always easily separable. In both forms 

 the legs and bill were coral-pink, but those of the pale form 

 were several shades lighter than those of the dark. In the 

 particular colony which I had under observation the dark 

 form was much the most numerous, in the proportion, I should 

 say, of quite three or four to one, and both were found in the 

 same nest. ^ N F Ticehuest. 



THE YOUNG OF TERNS. 



I have often remarked the swollen tarsi in young Terns 

 described in Mr. Robinson's note (antea, p. 169). This pecu- 

 liarity is, I believe, found in a greater or lesser degree in the 

 the young of all Limicolx. It is most conspicuous in the living 

 bird, but may be traced in some dried specimens ; in the Lap- 

 wing the thickening remains after the bird is able to fly. 

 I do not . remember seeing it except in Gulls and Plovers 

 and their allies, but the sight of the swollen ankle 



