1370.] MR. HUDSON ON THE BIRDS OF BUENOS AYRES. 671 
pl. viz.). The locality there given by Dr. Gray is erroneously stated 
to be Caraceas. More recently several examples of this species have 
been brought to Europe, and shows that this Squirrel, like several 
of its congeners, is very variable in its colouring, some of them 
being nearly wholly rufous, whilst others are white except on the 
dorsal streak, as shown in Dr. Gray’s figure (cf. Gray, Synopsis of 
American Squirrels, Ann. Nat. Hist. ser. 3, vol. xx. p. 422). 
3. A pair of Daubenton’s Curassows (Crax daubentoni, G. R. 
Gray), presented on the 29th of September by James Wright, Esq., 
having been received by that gentleman from 'Tucacas, a port in 
Northern Venezuela. This addition is of importance, as the species 
has not been previously received alive by the Society, and its exact 
locality was a little uncertain. 

A seventh letter* on the Ornithology of Buenos Ayres, by Mr. 
W. H. Hudson, C.M.Z.S., was read :-— 
* Buenos Ayres, April 23, 1870. 
“In my last letter I described the common Blackbird of this 
country (Molothrus bonariensis), but omitted some interesting par- 
ticulars, which I now furnish. I have found it most common in the 
vicinity of Buenos Ayres city, becoming rarer the further we go from 
it. It is fond of cultivated districts, but is oftener met with in open 
plains than in woods. Its eggs are not often found in the nests of 
birds that breed in wild forests—never in the nests of the Cuckoos 
and Thrushes. 
*‘T have never seen it attack any bird to get into its nest, and 
believe its eggs are invariably laid in the absence of the true pro- 
prietor. The Tijereta (Milvulus violentus), that constautly attacks 
and beats off birds of prey, would not be easily driven off by a female 
Blackbird ; and yet the Tijereta is the most imposed upon of any ; 
while, on the other hand, the Blackbird’s eggs are never found in 
the nests of some species that are not at all pugnacious, such as that, 
for example, of Serpophaga nigricans. 
‘A very remarkable circumstance is that the eggs of the Black- 
bird differ as much in form, size, and colour as its habits are irre- 
gular. Some are perfectly round, others oval, pointed, or elliptical. 
The commonest colours are pure white with very small pink spots 
thinly distributed, and reddish white thickly covered with brownish- 
red spots, the form of the spots on those darkly mottled being on 
different eggs round, oblong, and irregular. 
**Can it be possible that an imperfection of the sexual organs, 
producing this diversity in the eggs, causes also that looseness in 
its breeding-habits which makes this species so different from others ? 
According to Wilson, the Molothrus pecoris of the United States of 
North America lays but one egg in a nest, and lays its eggs all alike. 
The idea is perhaps fanciful, but has occurred to me, that all the birds 
I am acquainted with that build elaborate ingenious nests lay eggs 
* See Mr. Hudson’s previous letters:—No. I., P. Z. 8S. 1870, p. 87; II., ibid. 
p. 112; IIL, ibid. p. 158; IV., ibid. p. 832; V. and VL, ibid. p. 545. 
