EGGS OF BIRDS, 169 



though the kingfisher, for example, hides her shining white eggs in a 

 hole, yet that will not conceal them from the piercing- eyes of their 

 chief enemy, — the water-rat, — which, like all burrowing- animals, can 

 see with the least possible light. Many birds, also, which lay bright- 

 coloured eggs, make open nests : the thrush, for example, whose clear 

 blue eggs, with a few black blotches, are far from being concealed by 

 the plastering of clay and cow-dung, upon which they are deposited. 

 The green-bird (Fringilla chloris, Temminck) again, which builds 

 an open nest of green moss, lined with horse-hair, black or white, as it 

 can be had, lays clear white eggs, with red spots, precisely like those of 

 the common wren and the hay -bird, {Sylvia trochilus^) which build 

 covered nests, with a small side entrance ; while the house-sparrow 

 {Passer domesticus, Ray) lays eggs of a dull dirty green, streaked 

 with dull black, and always builds in holes, or under cover. These 

 objections will render it unnecessary for me to follow Darwin into ihis 

 fanciful account of the origin of the colour of eggs, which he ascribes to 

 the colour of the objects amongst which the mother bird chiefly lives, 

 acting upon the shell through the medium of the nerves of the eye ; for 

 if this were correct, we should have the green-bird and the red-breast, 

 instead of their white eggs, laying blue ones, like the hedge-sparrow 

 and the redstart. 1 



With respect to the eggs of birds, it has been remarked by Mr. 

 Knapp, 2 that in those of one hue, the colouring matter resides in the 

 calcareous part ; but where there are markings, these are rather extra- 

 neous to it than mixed with it. The elegant blue that distinguishes 

 the eggs of the firetail (Sylvia phosnicurus, Lath.) and of the hedge- 

 sparrow, though corroded away, is not destroyed by muriatic acid. 

 The blue calcareous coating of the thrush's egg is consumed ; but the 

 dark spots, like the markings on the eggs of the yellow-hammer, house- 

 sparrow, magpie, &c, still preserve their stations on the film, though 

 loosened and rendered mucilaginous by this calcareous matter, which is 

 partly taken up during incubation, the markings upon these eggs remain 

 little injured, even to the last, and are almost as strongly defined as when 

 the eggs are first laid. These circumstances seem to imply that the 

 colouring matter on the shells of eggs does not contribute to the various 

 hues of the plumage, but it is reasonable to conclude, are designed to 

 answer some particular object not obvious to us ; for though the marks 

 are so variable, yet the shadings and spottings of one species never 

 wander so as to become exactly figured like those of another family, 

 but preserve year after year a certain characteristic figuring. 



1 Insect Transformations, p. 35. 



2 Journal of a Naturalist, p. 230. 



