628 



SCIENCE. 



[N. S. Vol. XI. No. 277. 



proof of moult in the shape of such feathers 

 still in their sheaths, is furnished by a couple of 

 birds in the collection of Mr. Wm. Palmer 

 (No. 3283, September 17th and No. 3655, Oc- 

 tober 2d, Washington, D. C). I am of opinion 

 that it is perhaps only southern breeding birds 

 that moult so completely at this season, for no 

 northern specimens show it. Immature birds 

 from semi-tropical localities taken during the 

 winter months have either brown edgings or 

 blue edgings to the remiges and rectrices and 

 should not be mistaken for adults which have 

 dark, blue-edged primary coverts, instead of the 

 wholly brown ones which are characteristic of 

 the young bird. It is probable that young 

 birds, when they acquire precociouslj' new wings 

 and tail at the postjuvenal moult, like adults, 

 do not again moult then until the following 

 autumn ; but we do know that most brown 

 winged birds acquire five or six distal primaries, 

 a new tail and body feathers besides at a pre- 

 nuptial moult. Two birds in the New York 

 National Museum (Nos. 107844-45 Bahamas, "W. 

 I., March 11th) prove actual growth of all these 

 feathers, the worn brown primary coverts being 

 retained and many summer specimens furnish 

 evidence of having passed through a moult be- 

 fore reaching their breeding grounds, the rela- 

 tive amount of wear the different feathers show 

 proving them to be of different ages. Very 

 little is known about the prenuptial moult in 

 most species and it appears to be in many of 

 them a somewhat irregular affair spread over a 

 number of the winter months, but there is ample 

 evidence of its occurrence, the time, however, 

 being the only puzzling feature. 



First Nuptial Plumage. — The fourth stage of 

 plumage in the Indigo Bunting results from the 

 prenuptial moult which, as in most young birds, 

 is more or less incomplete. Consequently we 

 find breeding males almost wholly bright blue 

 or with only a scattering of blue feathers mixed 

 with the brown, gray or dull blue worn ones 

 belonging to the first winter plumage. The in- 

 dividual variation is great, but all young birds 

 may be differentiated by the ragged brown 

 primary coverts. Females undergo very little 

 moult and often none. 



Second or Adult Winter Plumage. — In August, 

 after the breeding season and relatively earlier 



than the time of the postjuvenal moult, the first 

 postnuptial moult takes place. At this time 

 all feathers are renewed in both sexes and the 

 identity of young and old is lost in most cases, 

 the former now acquiring for the first time blue- 

 edged primary coverts like those of the latter. 

 It is probable that a few year-old birds do not 

 assume primaries and coverts as deeply blue as 

 older birds, for in some winter specimens these 

 are dull, but the majority do, as proved by 

 birds taken in the midst of the moult. Spec- 

 imens of adults in winter or ' autumnal ' plum- 

 age, as it is commonly called, are scarce in 

 collections chiefly because the adults migrate 

 southward as soon as the moult is completed. 

 The remiges, their coverts and the rectrices 

 now acquired are, unlike those of the ju venal 

 stage, worn for a twelvemonth ; the body feath- 

 ers, largely blue with rusty-brown tips which 

 conceal much of the blue, are, on the other 

 hand, like those of the juvenal stage, renewed 

 by a prenuptial moult, the second. I have ex- 

 amined birds in the U. S. National Museum, 

 and in the American Museum of Natural History, 

 taken in Mexico, Yucatan and elsewhere which 

 show new growing blue feathers at various 

 points on the body, such specimens bearing 

 dates of February and March. It is of interest 

 to note in passing that the bright blue feathers 

 assumed either in young or old show a differ- 

 ent structure from those of the winter plumage 

 when examined under the microscope and can- 

 not be mistaken for them. The barbs are much 

 more lanceolate than those of the winter dress. 



Second or Adult Nuptial Plumage. — As just in- 

 dicated the adult breeding dress is acquired by 

 a partial moult which does not include the 

 wings nor the tail which are renewed in the 

 young bird. Before the prenuptial moult take? 

 place the blue of the body feathers is exposed 

 more or less by the wearing away of the 

 feather tips, and birds often appear brighter 

 than they do in the fall, but the moult itself 

 is more complete upon the body than in young 

 birds and fewer old worn feathers will be found 

 upon adult summer specimens. 



It is not necessary to trace the moults and 

 plumages further for later ones are but repeti- 

 tions of those already explained, and the few 

 birds which show immaturity during their sec- 



