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Show 156 MR. W. H. HUDSON ON T H E [Mar. 3, prived repeatedly of their nests, lay and even hatch four times in the season, thus laying, if the full complement be four, sixteen eggs. Probably the M. bonariensis lays at least twice (perhaps four times) that number. Before dismissing the subject of the advantages this species possesses over those that are its dupes, and of the real or apparent defects of its instinct, some attention should be given to another circumstance, viz. the new conditions introduced by civilized man, and their effect on the species. The effect of these altered conditions has been to make the species more numerous, and, by the removal of certain extraneous checks, to increase excessively those irregularities that must be concomitants of a parasitical instinct like that of this Molothrus. The procreant habits of M. bonariensis do in reality appear different in wild regions (where they were formed) from what they do in cultivated ones. In the former the birds are much rarer ; and it is, in such regions, an uncommon thing to find its eggs, and nests are there probably never overburdened with them. But in cultivated regions the birds congregate in orchards and plantations in great numbers, and avail themselves of all the nests, ill concealed as they must ever be in the clean and open-foliaged trees planted by man. III. Diversity in colour of eggs.-An extraordinary circumstance in connexion with the reproduction of M. bonariensis is the diversity in the coloration of its eggs ; I have heard of no other species laying eggs so varied. Perhaps as many as half the eggs, or nearly half, are pure unspotted white, like the eggs of most birds that lay in dark holes. Others there are sparsely marked with such exceedingly smooth specks of pale pink or grey, as to appear quite spotless until very closely examined. After the entirely white, the most common variety is an egg with white ground thickly and uniformly spotted or blotched with red. Perhaps the rarest variety is an egg entirely of a fine deep red. But between this lovely marbled egg and the white one with almost imperceptible specks, there is an infinite number of varieties ; for there is no such thing as " certain characteristic markings " in the eggs of this species, though, as I have already inferred, the eggs of the same individuals closely resemble each other. I will mention two more of the beautiful varieties :-one pure white with a few large or variously sized chocolate spots ; another, not uncommon, with a very pale flesh-coloured ground, thickly and uniformly marked with fine characters, that appear as if inscribed on the shell with a pen. This summer (1872-3) I have found five nests of the Yellow-breast (Pseudoleistes virescens). The first three nests were abandoned soon after being completed, owing to the confusion caused by the M. bonariensis, that began laying and breaking eggs in the nests before the Yellowbreast had laid any. The fourth nest was in a cardoon bush, and contained nine eggs, four of the Yellowbreast and five of the M. bonariensis : two of the parasitical eggs were pure white; the others were mottled. The fifth nest, also in a cardoon bush, contained five eggs-two of the Yellowbreast, and three parasitical. These three were of the variety most thickly mottled |