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Show 216 SEXUAL SELECTION : BIRDS. PART II. beauty during many years after they are fully matm:e ; this is tho case with tho train of the peacock, and w1th the crest and plumes of certain herons; for instance, the Ardea Lttdovicana ; 40 but it is very doubtful whether the continued development of such feathers is the 1·osult of the selection of successive beneficial variations, or merely of continuous growth. Most fishes continue increasincr in size, as long as they are in good health and haveb plenty of food; and a somewhat similar law may prevail with the plumes of birds. Cr;ASS V. When the adults of both sexes have a dis- . tinct winter and summer plumage, whether or not the male d~ffers from the female, the young resemble the adults of both sexes in their winter dress, or much more rarely in their summer dress, or they resemble the females alone; or the young may have an intermediate cha1·acter ; or again, they may differ greatly from the adults in both their seasonal plumages.-The cases in this class are singularly complex; nor is this surprising, as they depend on inhm·itance, limited in a greater or less degree in three different ways, namely by sex, age, and the season of the year. In some cases the individuals of the same species pass through at least five distinct states of plumage. With the species, in which the male differs from the female during the summer season alone, or, which is rarer, during both seasons,41 the young generally resemble the females,-as with the so-called goldfinch of North America, and apparently with the splendid Maluri of Australia. 42 With 40 J crdon, 'Birds of India,' vol. iii. p. 507, on the peacock. Audubon, ibid. vol. iii. p. 139, on the Ardca. 41 For illustrative cases see vol. iv. of Macgillivray's • Ilist. Brit. Birds;' on Tringa, &c., p. 229, 271; on the Machetes, p. 172; on the ChamclTius hiaticula, p. 118; on the Charadrius pluvialis, p. 94. 42 For the goldfinch of N. America, Fringilla tristis, Liun., sec <CIIAP. XVI. s EASONAL CIIANOES OF PLUMAGE. 217 the species, the sexes of which are . ,the summer and winter th alike durmg both the adults firstly in tl' . e . young may resemble which occ~rs muc'h m 1eJr wmlter dress; secondly, ore rare y in tb · dress '· thirdly' the y may be m. t'e rm d · et1 r bsu mmer these two states . and f, ·thl e Ja e etween from the adults' a~ ail om y, they may differ greatly seasons We hav . of the first of th f, · . e an mstance f I ese our cases m one of tl o ndia ( Buphtts coromandus) i . 1e egrets the adults of both ' 11 • whJCh the young and h sexes are white durin tl . t e adults becomina o·old b ff d . g 1e wmter, With the Gaper (A:ast en- u . urmg the summer . h omus oscztans) of I d' ave a similar case b t th n Ht we for the young and the :dultse o~o~ours are reversed ; ~n~. blaclhr during the winter, the adu~~~ ::~e:i::e g~·~ty uung t e summer 43 A . o w 1 e case, the young of .the r s ~nb ·~~stance of the second in an early state of 1 azOJ- l (Alca torda, Linn.), adults during th p umage, are coloured like the e summer . and the f white-crowned sparrow of N ·tl ~oung o the leucophrys ), as soon as fi d ord 1 AmerJCa ( Fringilla stripes on their heads wh. eh ge 'l have elegant white th 1 ' IC are ost by the d e o d during the winter 44 vV'th young an case, namely, that of the . ouncr I ~espect. to the third character between th Y o havmg an mtermediate e summer and · t ages, Yarrell4s insists tl t tl'. wm er a~ult plum- 1a us occurs w1th many Audubon, 'Ornith. Biograph ' . I . 'I;:ndbook.of the Birds of ~st:·~Il:·,P· ~7~· For the Maluri, Gould's I am mdebtcd to Mr Bl th ' v~ · 1. p. 3 ~8. Buphus; see also J erdon ; B' ·yd ffor l~formatwn in regard to the Ana s t omus, seA Blyth in '•I bisu' 1s8 6o7 Indta ' ' vo 1. m.. ·. JJ. 749. On the 44 On the Alca se~ 1\:I ·Ji- 'P· 173. On the Fringilla l~uco hn:c~ tvray, '!f~~>t. Brit. Birds,' vol. v. p. 347 11Crcaftor to refer to ~I y ' udubon, tbtd. vol. ii. p. 8::1. I shallltav~ wh!.tc. JC young of certain herons and egrets bcin 4" ' His tor y of Bn·t t·s h Birds ' vol g ' ·.l.. 1839 , p. lo-9. |