300 BULLETIN 113, UNITED STATES NATIONAL MUSEUM. ■ '; 



although days have been spent in the tern colonies for almost no other purpose 

 than the vain hope of seeing more of them. The bird was quite noticeable 

 among the enormous numbers of black terns; so much so that there is no spe- 

 cial need for any one to sacrifice the life of any of the common species under 

 the delusion that it may prove to be leucoptera when in hand. 



Nesting, — Yarrell (1871) says: 



The white-winged black tern nests in marshes, sometimes in company with 

 the black tern, where, as in Central Europe the latter preponderates, but in 

 large colonies of its own in southeastern Russia and Siberia, where it is the 

 dominant species. Its eggs, deposited on the floating vegetation in IMay and 

 June, are usually three in number, of an olivaceous-buff, boldly blotched, and 

 streaked with dark brown, and spotted with gray of different shades. Average 

 measurements about 1.35 by 1 inch. 



Eggs.—Movvis (1903) states: 



They arrive at their summer haunts in the month of May and disappear in 

 July and August. The eggs of this species are three or four in number, with 

 many grayish spots, and some larger blackish red ones, the ground color' 

 being dull yellowish olive. They are of a rotund form. The male and female 

 birds sit on them in turn and show much anxiety for their safety, flying at 

 and about all intruders. 



The eggs of this species seem to be indistinguishable from those of 

 the common black tern. The measurements of 42 eggs, in various 

 collections, averaged 34.9 by 24.9 millimeters; the eggs showing the 

 four extremes measure 37 by 25.1, 35 by 26, 33.5 by 24.4 and 33.5 

 by 23 millimeters. 



Plumages. — Yarrell (1871) describes the plumage changes as fol- 

 lows : 



The nestling is of a nearly uniform rufous-buff, slightly darker on the 

 throat; the crown and back streaked and mottled with blackish-brown. The 

 immature bird in August has the bill livid brown; lores and forehead white; 

 crown and nape brownish-gray ; a dark streak behind the ear-coverts. Sides 

 of the neck white, tinted with buff; upper back and scapulars slate-gray, 

 tipped or overlaid with brown, which gradually wears off; back gray, mottled 

 with brown, rump white, passing to gray on the tail-coverts; tail feathers 

 gray, dai'ker and browner at tips ; primaries darker on inner webs than in the 

 adults; under wing-coverts and under parts white. By the end of the follow- 

 ing summer the brown tips have completely passed away, leaving only a mottled 

 bar along the carpals to indicate immaturity; and in the following spring, 

 when the bird is nearly 2 years old, it assumes the black nuptial garb. The 

 tail feathers, however, do not become quite white for some years, and it may 

 be that this takes longer with the females than with the males ; otherwise there 

 appear to be no appreciable external differences between the sexes when fully 

 matured. In the autumn molt the black portions of the plumage become white 

 on the head, neck, and underparts, and slate-gray on the mantle. A specimen 

 In the editor's collection, obtained near Valencia, in Spain, on the 25th of 

 July, presents » remarkably piebald appearance. Some black is never absent 

 from the nape and ear coverts, and in mature and vigorous birds the black 

 of the under parts soon begins to make its reappearance. 



