156 mr. w. h. Hudson on the [Mar. 3, 



prived repeatedly of their nests, lay and even hatch four times in the 

 season, thus laying, if the full complement he 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 civi- 

 lized 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 diver- 

 sity 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 mark- 

 ings" in the eggs of this species, though, as I have already in- 

 ferred, 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 {PseudoJeistes 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 



