122 PROcEEDrNGS OF THE [Sept., 1886. 



Mam'gault and C. B. Golson, was appointed to collect data concern- 

 ing tlie Earthquake of August 31st. 



The following paper was read : 



STEHIf A FLUVIATILIS AEB STERNA FORSTEHI. 



BY ELLISON A. SMYTH, JK. 



In 1831 Swainsou and Eichardsou, in their Fauna Boreali-Americana, gave 

 a description of a Tern under the well known name of Sterna Mrundo. They 

 however, notice some differences from the S. hirunclo of Linnaeus. 



In 1834, Nuttall, in a foot-note, calls attention to this Tern and pro^Doses to 

 call it Sterna forstevL 



In 1839, Audubon, on Plate 409, fig. 1, of his Ornithology, figmres the same 

 bird, in the immature or Winter phamage, however, in w^hich plumage alone 

 that Author seems to have known the bird, as Sterna JiaveUi. 



To G. N. Lawrence is due the credit of having firmly established the validi- 

 ty of Sterna forsteri, by giving complete descriptions and b^'' showing its true 

 xeXiitxon. to Sterna Mrundo, (or, we should say, Sterna fluvtatilis^ of Nauman, 

 as the American ally of Sterna Mr undo is now known). 



The object of these remarks is merel}^ to bring before the Society some of 

 the easily recognized differences between these two Terns, viz.: Sterna fluviati- 

 Us and S. forsteri. 



To the casual observer, in handling the two birds together, forsteri will 

 show up as the heavier in every way, and on comparing many examples, this 

 will be found pretty constant. 



The bill xn. forsteri wiU be found a little longer and noticeably heavier at the 

 base. Even young specimens of fluviatilis, in which stage the bill is generally 

 deeper than in the adult, scarcel}^ if ever, approach the full depth observed in 

 foi'steri. The bill ot fluviatilis \vill always show slighter proportions. 



In the Sidwlt fluviatilis the bill is coral at the base, gradually deepening into 

 black, and with a yellowish tip ; the young of the same species has only a trace 

 of yellowish near the base of the biU, and the rest of it is black, thus being 

 very hke the bill ot forsteri, but here the size is a guide, forsteri being stouter. 

 Tliis change in the bill of fluviatilis is exactly a counterpart of what occurs in 

 S. mperciliaris, ( Least Tern). 



The leaden color of the belly plumage of Sterna fluviatilis, in full plumage, 

 will easily distinguish it from, forsteri at the season when both have the black 

 of the pileum complete ; and though the white breast and belly plumage 

 shown by most Fall and Winter specimens of fiuvioMlis is hke that of forsteri, 

 the pileum will be a guide ; that oi forsteri, with the exception of a black bar 

 through the eye, almost disappears, or seems as though hidden under a layer 

 of whitewash, while Sterna fluviatilis only whitens a little on the forehead and 

 retains the black on the posterior portion of the pileum unimpaired. 



