230 BULLETIN 20 3, UNITED STATES NATIONAL MUSEUM 



and green caterpillars, but dragon flies and may-flies are the chief staples. 

 Slugs, winged ants, white cabbage butterflies and moths are also on the menu. 

 From the time the young hatch until they are five days old the parents 

 swallow the faecal sacs. After that they carry them away from the nest and 

 place them on the branches of neighboring trees — frequently using dead branches. 



She gives a detailed account of the development of the young and 

 their manner of leaving the nest naturally on the tenth day. During 

 the 6 days when she thought it safe to handle them without driving 

 them out of the nest too soon, one increased in weight from 22 grains 

 to 141, and another from 24 to 147 grains. 



Plumages. — The sexes differ slightly in the juvenal plumage. The 

 young male is olive-brown above ; the wings are blackish, the primaries 

 edged with bluish-leaden-gray; the wing coverts, secondaries, and 

 tertials are margined with olive-green, and there is a white patch near 

 the base of the primaries, as in the adult; the tail is much like that 

 of the adult ; the under parts are brownish, tinged with yellowish on 

 the throat and abdomen ; the lores and two submalar streaks are dusky, 

 and the superciliary stripe is yellowish white. The young female is 

 similar, but has dull brown wings and tail with greenish instead of 

 bluish edgings, and the white area in the primaries is smaller, more 

 dingy and sometimes obscure. 



A partial postjuvenal molt occurs in late July and August involv- 

 ing the contour plumage and the wing coverts but not the rest of 

 the wings or the tail, producing a first winter plumage in which the 

 sexes become decidedly differentiated and not very different from the 

 adults at that season. This is one of the few wood warblers in which 

 the fall plumage is very much like the spring dress. In the young 

 male the blue of the upper parts is not as clearly blue as in the adult ; 

 the feathers of the back are faintly edged with olive-green, those of 

 the black throat veiled with dull whitish, and the abdomen is tinged 

 with yellowish. The young female differs from the fall adult in 

 being greener above, without bluish tinge, and more buffy or yellowish 

 below. 



There is a limited prenuptial molt about the head, and wear has 

 removed most of the edgings and fading has made the under parts 

 clearer. At this age, young birds can be distinguished from adults 

 by the worn and dull brown wings and tail. Subsequent molts and 

 plumages, in which young and old are alike, consist of a complete 

 postnuptial molt in July and August and a limited prenuptial molt 

 about the head. The adult male in the fall is only slightlj'^ tipped with 

 greenish above and with whitish on the black throat, which may be 

 somewhat less in extent. 



Food. — No thorough study of the food of the black-throated blue 

 warbler seems to have been made, but probably all of the items men- 



