1870.] | MR. HUDSON ON THE BIRDS OF BUENOS AYRES. 549 
certainly would have given it a distinguished place in the ‘Origin 
of Species ;’ and he could not have found any more remarkable case 
for illustrating the ‘mistakes and imperfections to which instinct 
is liable,’ and which he considers favourable to his theory. 
«« There are few small birds here into whose nests the female 
Blackbird does not intrude; and great is the domestic confusion in- 
troduced by her visits. She does not choose nests for their size or for 
their architects being hard or soft-billed birds, but lays her eggs 
indiscriminately wherever she can. I have never found her eggs in 
the nest of the Churinche (Pyrocephalus rubineus), probably because 
that pugnacious little bird remains by it and is able to beat her off. 
I have also observed that the Blackbird never lays in domed nests, 
though parties of them are constantly seen about the ovens of the 
Oven-bird (Furnarius), climbing over, peering into, and even entering 
and examining them very curiously. It would be difficult to enumerate 
all the little birds who are compelled to rear the young Blackbirds ; 
but their favourite nests, probably because easiest discovered, and 
undefended against their intrusion, are those of the Cachila (Anthus 
correndera), the Chingolo (Zonotrichia pileata), the Jilquero (Chry- 
somitris barbata), the Tiyereta (Milvulus violentus), and the Yellow- 
breast (Pseudoleistes virescens). 
“The nests of the last two are particularly preferred; indeed I 
seldom find a nest of either of them but it contains more eggs of the 
Blackbird than of the rightful owners, while from one or two to halt 
a dozen female Blackbirds are usually to be observed near it. 
“« They frequently begin depositing their eges before the nest is 
finished, upon which it is generally abandoned ; and often so many 
eggs are laid in a nest, that, even if they are set on, few or none of 
them can be hatched. The nest of the Tyereta is usually found 
with from five or six to a dozen Blackbird’s eggs in it, that of the 
Yellow-breast, which is deeper, with from fifteen to twenty ; but 
what the nest contains are seldom all the eggs that have been laid 
in it; for, by looking on the ground under the tree or bush, many 
more will frequently be discovered, thrown down by the female 
Blackbird. Another’ destructive habit of this bird (destructive to 
its own increase as well as to that of other species) is its habit of 
pecking holes in the eggs it finds in the nest where it lays. This 
is not a fixed, invariable habit, but irregular, as are its reproducing- 
instincts. Sometimes the shells are so broken that the yelk is spilt 
in the nest ; at other times they peck small holes in the shells; and 
sometimes they strike their bill into one egg and fly away with 
it, as a Pigeon does with the shell of an egg it has just hatched. 
This I have seen them do; and I have often found an egg with a 
hole in it several feet from the nest, doubtless removed in this way. 
Some nests are found containing a dozen or twenty eggs, every one 
with holes pecked in them. In the laying-season each female is 
generally attended by one or two, and sometimes three males, who 
quietly remain near while she is on the nest. The Blackbird also 
drops its eggs on the ground; and I continually find these lost eges 
on ploughed fields, roads, and spots of barren earth. 
