Moreover, I have a note to the effect that near Eyam, in 1887, some Jackdaws were nesting among the branches, after the manner of Rooks. In the 'Naturalists' Journal' (vol. vii. No. 72, June, 1898) a similar occurrence is recorded.
III. When birds build covered nests the eggs are white, spotted finely with red, black, or brown, e.g. the Wren's, Chiffchaff's, Swallow's; or pure white, e.g. the Dipper's. The House- and Tree-Sparrows are exceptions.
IV. Nocturnal birds lay white eggs, as the Short-eared Owl; or nearly white, as the Nightjar. Protective colouring is not needed in such cases, as the birds sit on their eggs throughout the day.
V. The eggs of the Accipitres are safe under the parental guardianship. They are pure white, white slightly spotted with red, or boldly blotched with red, or in some cases the ground colour is entirely hidden by the overlying red.
Here again the exceptions to the rule present great difficulties. Some of them are interesting enough to have attracted the attention of Dr. Wallace and Prof. Poulton.
(a) All the breeding habits of the Cuckoo are strange and abnormal. Until more is known about them we cannot hope for a satisfactory explanation of the variability of its eggs.
(b) It is a surprising fact that the Wood-Pigeon, which makes an open nest, lays pure white eggs. Dr. Wallace[1] and Prof. Poulton[2] give the following explanation:—They suggest that the egg is white as a protection from below; that the Wood-Pigeon builds a flimsy wicker nest, through the bottom of which the eggs can be seen; but that, being white, they are inconspicuous against the blue sky. [Dr. Wallace expresses it rather differently. After remarking that light may be seen through the nest from below, he says:—"It is a difficult matter to discover, from beneath, whether there are eggs in the nest or not, while they are well hidden by the thick foliage above."] It seems hardly possible that this is the true explanation. Wood-Pigeons' nests are not always of the wicker type; and, if it is an advantage
