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Show 214 DARWINISM CJIAl'. hugo goatsuckers-build very similar nests, and their white eggs are protected in the same mann~r. Some }argo and powerful birds, as the swans, herons, pehcans, cormorants, and storks lay white ecrO's in open nests ; but they keep careful watch ' over them, abnbd are able to drive away m. tru dc rs. 0 n the whole, then, we sec that, while white eggs arc conspicuous, and therefore especially liable to attack by egg-eating anima}:;, they are concealed from observation in many and various w:t.yFi. Wo may, therefore, assume that, in cases where there seem. to be no such concealment, we are too ignorant of the whole of the conditions to form a correct judgment. We now come to the large class of coloured or richly spotted eggs, and here we have a more difficult task, though many of them decidedly exhibit protective tints or markill g:=;. There arc two birds which nest on sandy shores-the lcFisrr tern and the ringed plovcr,-and both lay sand-coloured cggR, the former spotted so as to harmonise with coar"o shingle, tlJC latter minutely speckled like fine sand, which are the kin d~ of ground the two birds choose respectively for their nests. "The common sandpipers' eggs assimilate so closely with the tints around them as to make their discovery a matter of no small difficulty, as every oologist can testify who has searched for them. The pewits' eggs, dark in ground colour and boldly marked, are in strict harmony with the sober tints of moor and fallow, and on this circumst:nH·c alone their concealment and safety depend. The divers' eggs furnish another example of protective colour; they arc generally laid close to the water's edge, amongst drift and shingle, whore their dark tints and black spots coJI< " <'<~ l them by harmonising closely with surrounding objects. The Finipes and tho great army of sandpipers furnish innumerable instances of protectively coloured eggs. In a.ll 1110 instn.nces given the sitting - bird invariably ]c:wcs the r~~s uncovered when it quits them, and consequently their, af<'I.Y depends solely on tho colours which adorn them." 1 Tho wonderful range of colour and marking in tho eggs of I he guillemot may be imputed to the inaccessible rocks on which 1 C. Dixon, in Seebohm's llistm·y qf British Birds, vol. ii. Jntrodnctiou, p. xxvi. Many of the other examples here cited are taken from the same valu· able work. Vlli ORIGIN AND USES OF COLOUR IN ANLMALS 215 it breeds, giving it complete protection from enemies. Thus the pale or bluish ground colour of the eggs of its allies, tho auks and puffins, has become intensified and blotched and spotted in the most marvellous variety of patterns, owing to there being no selective agency to prevent individual variation having full sway. The common black coot (Fulica atra) has eggs which arc coloured in a specially protective manner. Dr. William Marshall writes, that it only breeds in certain localities where a large water reed (Phragmitcs arundina.cca) abounds. The 9ggs of the coot arc stained and spotted with blu.ck on a yellowish-gray ground, and tho dead leaves of the reed are of the same colour, and arc stained black by small parasitic fungi of tho Urcdo family; and these loaves form the bod on which the eggs arc laid. The eggs and the leaves agree so closely in colour and markings that it is a difficult thing to distinguish the eggs at any distance. It is to be noted that the coot never covers up its eggs, as its ally tho moor-hen usually docs. Tho beautiful blue or greenish eggs of the hedge-sparrow, the song-thrush, the blackbird, and the lesser redpolc seem at first sight especially calculated to attract attention, but it is very doubtful whether they are really FiO conspicuous when seen at a little distance among their usual surroundings. For the nests of those birds arc either in evergreens, as holly or ivy, or surrounded by tho delicate green tints of our early spring vegetation, and may thus hrmnonisc very well with the colours around them. Tho great majority of the eggs of onr smaller birds are so spotted or streaked with brown or bln.ck on variously tinted grounds that, when lying in tho shadow of the nest and surrounded by the many colours and tints of bark and moss, of purple buds and tender green or yellow folia.ge, with all tho complex glittering lights and mottled shades produced among these by the spring sunshine and by sparkling raindrops, they must have a quite different aspect from that which they possess when we observe them torn froi?- .their natural surroundings. We have here, probably, a Similar case of general protective harmony to that of tho green caterpillars with beautiful white or purple bands and spots, which, though gaudily conspicuous when seen alone, |
