52 



SCIENCE. 



[Vol. XXI. No. 521 



unifoitn in color no marked difference is produced by the pro- 

 cess. Theabrasion begins soon after the aiitumal moult and con- 

 tinues throughout the year, being effected by the general wear 

 and tear on the plumage and by the action of the bird itself in 

 cleaning its feathers by drawing them through its bill. The 

 margin of the feather — that is the terminal portion of the barbs — 

 seems to become brittle and break off at a slight touch, the point 

 at which the fracture occurs being on the line where the color 

 changes, in parti-colored feathers. In this -way the color of a 

 bird may be entirely changed without the loss or gain of a 

 feather, for owing to the shingled arrangement of the plumage 

 only the terminal portion of the feather is seen, and when this is 

 worn off the central and basal portion, which is frequently differ- 

 ently colored, comes into view. 



The series of snow-buntings collected in Greenland by the late 

 Peary expedition, which have passed through my hands, taken 

 in connection with winter specimens from Pennsylvania, show 

 this method of plumage change very well. Taking the feathers 

 of the back, for instance; in the winter birds we find them so 

 broadly tipped with white and brown as to give a light-colored 

 appearance to the bird; in the summer specimens, however, the 

 light tips have been entirely lost and the back becomes solid 

 black. The actual shape of these feathers has changed too, for 

 while those of the winter birds were oval, those of the summer 

 specimens are found to be pointed, with the sides somewhat con- 

 cave. This was the shape of the black central portion of the 

 feathers in the winter, and when the light margin has been worn 

 off the black portion is, of course, all that remains. This change 

 of shape in the feathers, due to abrasion, is best seen, however, 

 in the curlews and other birds in which the back and rump 

 feathers have peculiarly lobed black centres with light-re-cclored 

 margins. The breeding birds of these species will be found to 

 have these feathers deeply sinuated along the margins due to the 

 loss of the light portions, between the black lobes, in striking 

 contrast to the oblong oval feathers of the fall plumage. 



In birds which experience a loss of the tips of the feathers by 

 abrasion, but which, owing to the manner of coloration of the 

 feathers do not show any marked change in the general colora- 

 tion of their plumage, as in the common Song Sparrow, the fall 

 specimens can still be distinguished from spring ones at a glance ; 

 as the plumage in the former is long and blended while in the 

 latter the feathers have the appearance of having been clipped 

 with shears. 



As has already been said, these two methods of changing 

 plumage (1) by a complete moult, and (3) by abrasion, take place 

 in all birds, but the time and extent of the changes differ in dif- 

 ferent species. 



Our passerine birds may be grouped in three classes according 

 to the changes which take place in their plumage during the 

 year. The most usual system is (1) a complete moult in the au- 

 tumn or late summer and (2) an abrasion of the tips and margins 

 of the feathers in the spring accompanied by a more or less ex- 

 tensive renewal of the smaller body of feathers. 



In some species the acquisition of new feathers in the spring is 

 so slight that it is scarcely apparent and can only be detected by 

 careful scrutiny while in other cases considerable patches of 

 feathers are renewed. 



In the Sharp-tailed Finch, of which I have examined a series 

 of eighty specimens taken during every month of the year on the 

 New Jersey salt marshes by Mr. I. N. DeHaven and myself, I 

 And a considerable acquisition of new feathers taking place in 

 April; in some individuals even the tail feathers are being re- 

 newed, which is not surprising as owing to the habits of the bird 

 the plumage must become very much worn. Many male birds 

 which require several years to attain their full adult plumage ac- 

 quire some of the feathers characteristic of the adult plumage at 

 this spring moult. The White-throated Sparrow, for instance, ac- 

 quires additional white feathers on the throat and head, and yel- 

 low ones in front of the eye, and the Myrtle Warbler experiences 

 an increase in the yellow feathers on the sides of the breast. 



The second system of moulting consists of (1) a complete moult 

 in the autumn or late summer and another moult in the spring, 

 which is either complete or excludes the remiges and rectrices. 



Such birds as the Scarlet Tanager, Indigo bird, etc., are exam- 

 ples of this class. Owing to the fact that many of them winter 

 in the tropics it is difficult to obtain specimens showing the 

 progress of the spring moult, and we are forced to a comparison 

 of fall and spring birds. The Goldfinch, however, which can be 

 obtained throughout the year in this latitude, shows the double 

 moult very nicely, and specimens taken in April and September 

 will be found respectively to be acquiring and losing the familiar 

 bright yellow plumage, the gray feathers of winter appearing in 

 the fall birds and disappearins in the spring ones. 



The third system of moults seems the most complicated of the 

 three, and was first pointed out by Mr. Frank M. Chapman in the 

 case of the bobolink. 



This bird has a complete moult in the late summer, then another 

 complete moult in the early spring before it starts north from the 

 tropics, and between that time and the breeding season an exten- 

 sive abrasion, which again completely alters the appearance of 

 the plumage. (See The Aul, 1890, p. 120.) 



Specimens of the Rose-breasted Grosbeak which I have re- 

 cently examined, taken in South America, seem to indicate that 

 this species has a similar system of moulting to that of the Bobo- 

 link. 



So far as I can ascertain, the adult male in fall assumes the 

 striped brown dress of the female, but differs from it in having 

 bright pink under wing-coverts and a marked pink suffusion on 

 the breast. Opposed to this is the well-known black and white 

 plumage of the breeding bird with its brilliant pink breast. Now 

 the South American birds above alluded to are different from 

 either of these. They possess the full plumase of the breeding 

 bird, but every feather has a light brown or buff edging which 

 givr's the bird a " veiled " appearance and conceals to a certain 

 extent the striking markings of the nuptial dress. 



These specimpns indicate pretty clearly that in addition to the 

 annual fall moult the male Rose breast has a complete moult during 

 the winter or early spring, assuming at this time a dress which 

 differs decidedly from the breeding plumage, but which changes 

 into it by means of extensive abrasion. 



The lower orders of birds have as a general thing still morecom- 

 plicated moults than are found in the Passeres, and of most of them 

 comparatively few of the details are known. 



In consideration of these facts as well as the great interest that 

 this study possesses, I cannot but recommend to all collectors to 

 have this matter In view in making future additions to their 

 collections and to look over the material which they already pos- 

 sess with an eye to the moult, feeling sure that they will be well 

 repaid for their pains. 



LETTERS TO THE EDITOR. 



**« Correspondents are reqiiested to be as brief aft possible. The writer's name 

 is in all cases required as proof of good faith. 



On request in advance, one hundred copies of the number containing his 

 comTnunication will he furnished free to any correspondent. 



The editor willbe glad to publish any queries consotiant with the character 

 of the journal. 



Comparative Longevity. 



Among mammals the epoch of maturity is usually stated as 

 reached in one-fifth of the animal's life. Thus the ages of ma- 

 turity and periods of life of several forms are about as follows: 

 horse, bull, four to twenty; sheep, two to ten; rabbit, one to five; 

 but there are exceptions, such as the cat, which matures in one 

 year and may live twenty. 



It is assumed that man matures at twenty, and hence, by the 

 rule, should live to be one hundred, as does the elephant, which 

 matures in its twentieth year. But, I think that writers upon 

 longevity, such as Huf eland, Flourens, Quatrefages, Thoms, etc., 

 when commenting upon these relationships, have overlooked the 

 fact that the general rule holds better for the lower races of men 

 who mature sooner than the civilized, to whom the retardation 

 of early development is an advantage, as it prolongs the plastic, 

 receptive period. 



The helplessness of the human infant at birth, and the length 

 of time it needs parental care, in these respects differing from 



