206 On the so-called Sterna Portlandica. 



lower mandible red as far out as the gonys, but in by far the 

 greater number of cases, where the mantle has nearly lost 

 its rusty spotting, and the forehead becomes pure white, the 

 bill is nearly and in some examples, entirely black, with but 

 a slight reddishness at the base. 



With the greater or less amount of black on the bill is 

 usually correlated a darker or lighter color of the feet and 

 tarsi, but this rule also has one or two exceptions in the 

 series. Now to return. The black-billed birds taken in 

 July and August cannot be birds hatched this season. That 

 is manifestly impossible, for they are all in perfectly devel- 

 oped plumage, and the mantle is as clear and immaculate as 

 in mature specimens. What then are they? They are birds 

 that have completed the first year only of their existence ; 

 birds that in the fall of the previous year had the mantle 

 slightly obscured by brownish blotchiugs, the bill nearly 

 black and the tarsi and feet dark : in short, birds like the 

 ones we have just been examining. The dark color of the 

 bill and legs has since spread and intensified. Indeed one 

 of the October specimens is so nearly like these summer 

 birds, that had not its age been carefully determined by dis- 

 section, we should hesitate before calling it a bird of this 

 season. Its bill and feet are quite as dark as the average of 

 the summer specimens, and the mantle has become nearly 

 immaculate. Now in this same category we would place 

 Sterna Portlandica, referring its parentage of course, as 

 before stated, to macrura instead of hirundo. Only one 

 more question remains to be answered, namely ; why are 

 these black-billed birds so rare, if they represent a regular 

 sta^e or plumage of species so common as S. macrura and 

 S. hirundo ? Here we are obliged to confess ourselves nearly 

 at fault and can offer little more than conjecture. 



It is, however, nearly certain that neither species while in 

 this plumage breeds, and this is decidedly the opinion of the 

 gentlemen to whom we are indebted for the most interesting 

 and important specimens, an opinion founded moreover on 



