On the so-called Sterna Portlandica. 203 



What then are its true affinities ? Let us take up a specimen 

 of Sterna macrura, and ignoring for the moment all discrep- 

 ancies of color, compare it carefully with Portlandica. Part 

 for part it agrees perfectly ; not a measurement of bill, feet, 

 tarsi, wings or tail, but can be exactly matched in the series 

 of -macrura before us. Undeniably then the difference is 

 'purely one of color. 



But it may be urged the Arctic tern never in any plumage 

 possesses a black bill and feet. True it has never been knoivn 

 to have these parts so colored, neither has S. hirundo ; and 

 yet we have just traced a bird of the size and proportions of 

 hirundo, but with the bill and feet black, or nearly so, 

 directly and unmistakably up through closely connecting 

 forms, into the ordinary typical plumage of that bird. Now 

 why should not S-. macrura be subject to the same variations 

 of color? It is a bird very closely allied to hirundo and 

 with — so far as is known — nearly the same seasonal changes 

 of plumage. What can be more likely than that S. Port- 

 landica bears the same relation to macrura that our black 

 billed bird does to the adult hirundo. With as good a series 

 of skins of Sterna macrura as that now at our command of 

 S. hirundo, there can be but little doubt that this point could 

 be directly established. At present we have only analogy 

 to reason by, but the indirect evidence is most strong. The 

 fact that Portlandica has the rump white is very pertinent, 

 inasmuch as Sterna macrura is the only species among those 

 we have named, whose nestlings have not that part more or 

 less washed with slate or pearly blue. Two specimens of 

 undoubted young macrura before us, though not sufficiently 

 feathered to fly at the time of their capture, still have the 

 rump of most immaculate whiteness. Our specimen of 

 Portlandica has the bill, tarsi and feet, absolutely black; but 

 in this respect it probably represents an extreme and perhaps 

 accidental limit of variation. 



The Smithsonian specimen we have never seen, but in the 

 past connection, mark the following clause taken from Dr. 

 November, 1S75. 15 Ann. Lyc. Nat. Hist., Vol. xi. 



