234 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. 



buffy edgings in the shape of transverse bars ; a partial molt of the 

 body plumage also takes place at this time. Young birds, in their 

 first winter plumage, may be distinguished from adults by their 

 shorter and less deeply forked tails with some brownish mottling, 

 and by their darker primaries, which are less silvery and have the 

 white spaces more sharply contrasted with the black. 



x\. complete prenuptial molt in February and March produces 

 the first nuptial plumage, which is usually indistinguishable from 

 the adult. Some young birds in nuptial plmnage have wings some- 

 what like those of the first winter plumage; others renew the first 

 winter plumage of the head ; but, as a rule, young birds become in- 

 distinguishable from adults when 9 or 10 months old. 



Adults have two complete molts — a prenuptial in February and 

 March and a postnuptial in August — and two distinct plumages. 

 The adult winter plumage, which Audubon described as Sterna ha- 

 velli, is quite different from the well-known spring plumage. The 

 crown is usually largely and sometimes wholly white, though dusky 

 spots are often scattered through it, and there is a more or less dis- 

 tinct nuchal crescent of dusky tipped feathers; there is a distinct 

 black space, including the eye and the ear coverts; the lateral tail 

 feathers are shorter than in the spring, and the primaries, when 

 freshly grown, are beautifully silvered. 



Food. — Being so largely a bird of the marshes, Forster's tern feeds 

 less on fish and has a more varied bill of fare than the other terns. 

 It maj'^ be seen catching insects on the wing, as well as hovering over 

 the pools, its bill pointing straight downward, looking for tiny mor- 

 sels of food on the surface. It sometimes makes a diving plunge 

 into the water, but more often it drops down lightly or swoops grace- 

 fully along the surface, picking up its food without wetting its 

 plumage. Rev. P. B. Peabody (1898) notes that "the first apparent 

 spring-time food consists of dead fish and frogs and other aguafica 

 that have perished in the winter ice, and are being revealed as the 

 latter melts beneath the sun." Mr. W. L. Dawson (1909) says: 



When the insects are flying well the terns prefer to hawk. Dragon flies and 

 caddis flies are favorite quarry, and in pursuit of the latter the birds will often 

 rise to a height of several hundred feet. 



The birds shot in Louisiana by Audubon (1840) " wore engaged in 

 picking up floating coleopterous insects." 



Behavior. — I have never been able to discover anything distinctive 

 in the flight of Forster's tern ; it is as light and graceful as that of the 

 common tern, which it closely resembles in every particular. Al- 

 though quite different in the fall, the two species can not be easily 

 distinguished in the spring ; the white breast of the former is often 

 obscured by shadow, the slight difference in size inappreciable, and 



