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Show 80 REX.UAI~ SELECTION : BIRDS. ]'.\TI.T H. 'ther retained for life or are tbe males when adult arc Cl l or and brecding-d 1 . · t 1e summ ' Periodically rcnewe c nnng b ]- cl na1wcl skin about , season. At t 1u ·s sen son the ea \. an 'th some herons, l l colour as Wl the head frequent y c lan~ell-birds' just noticed, &c. In ibises gulls, one of the e 1 .. flatable skin of the ' · · 1 1 ceh t 1e m < the white lbls, t 1e c 1 '-.' f tl e beak then become l 1 b I IlOrtwn o 1 ' throat, anc t 10 nsa. rails Gallicrex cristatus a 1a rgo crimson.n In one of the 1 l ' . tl1is same period on reel caruncle · 1 , ::.}opec c urma t lS c e' e . . o 'th a thin horny orcs . 1 So 1t 1s w1 ' · the head of the ma c. 1' p erythrorhynclws ; f f the pe 10ans, · on the Leak o one 0 . these horny crests are for I ttfter the breedmg-scason,l f taas aml the f'lwre · f the heac s o s b ' shed, like horns rom . N , cla was found covered of an island in a lake. m72 e' a ' 'th tbese curious exuvu:c. . ·d'na to the w1 • tl lumaae accor 1 o Changes of colour 1~ a c~~t~le ani~mal moult, secondly season clepencl firstly o . tl i'eathers themselves, l h a of colour m le 1 · 1 on an actua c ano.e reel marains being pcnoc-and thirdly on theu cllull-cotlho~ce I)roce~ses more or less 1 l l or on t 1esc I · y ical y s lee' d. f the dcciduary margms ~la combined. rrhe .shed m~l~eddina by very young bmls be compared with the s . . b ost cases arises from 0 f their down ; for the do" n . m m. 73 . f th fi ·st true feathe1s. the snmmits o e ~I b' ·ds ·which annually undergo a With respect to t 1e fiu. l e kinds for instance It th ·e arc rst y, som ' . double mou , er - ' 1 . 1 ) and curlews, lll 11 1 vers (G areo re ' ' snipes, swa ow-p o bl nch other and do not which the two sexes resem e ; do not know whether chanbo·e colour at any seahs~nl. d \Varmer than the the w.m ter-pl umaocr e 1•8 t 1C ~er an il 'Lo.nd n.nd \Vater,' l G7, P· ~!)4.1 Soc' l8G0 p. 58D. E 1. t . 'rroe LJ00 • • ' ;~ l\1r D G. I 10, m ·, 1.t 1 by p L Sclatcr. ;a 'Nitz;ch's Ptcrylogrnphy, Cl l CL • . · ~ 18G7, p. H. DOUDLE ANNUAL liiOULT. Sl Rummer-plumage, which -=eems, wl1en there is no chango of colour, the most probable cause of a double moult. /:)econclly, there are birds, for instance certain species of Totanns and other grallatores, the sexes of which resemble each other, but have a slightly different summer and winter plumage. ~rbe difference, howe,·er, in colour in these cases is so slight that it can hardly be an advantage to them; and it may, perhaps, be attributed to the direct nction of the differ nt conditions to which the birds are exposed during the two seasons. Thirdly, there arc many other birds the sexes of which are alike, but which are widely different in their summer and winter plumage. :Fourthly, there are birds, the sexes of which differ from each other in colour; but th~ .. females, though moulting twice, retain the same colours throughout the year, whilst the males undergo a change, sometimes, as with certain bustards, a great ehange of colour. Fifthly and lastly, there are birds the sexes of which differ from each other in both their summer and winter plumage, but the male undergoes a greater amount of change at each recurrent season than the female-of which the Huff (JJfachetes pttgnax) offers a good instance. vVith respect to the cause or purpose of the differences in colour between the summer and winter plumage, this may in some instances, as with tlle ptarmigan, 74 servo during both seasons as a protection. vVhen the difference between the t'Yo plumages is slight it may perhaps be attributed, as already remarked, to the i 4 'fhe brown mottled summer plumage of the ptarmigan is of as much importo.ncc to it, as 11 protection, as tho white winter plumnge; for in Scalldino.via, <luring tho spring, wh<:n tho snow hns <.lilmppcarcd, this bird is known to su1fur greatly from birds of prey, before it has acquired its summer dress: sec ".ilholm YOil '\Vri,.ht ill LlorLl 'Gnmo 13inls of Swcdou,' l8G7, p. 125. 0 ' • ' vo~ r~ o |
