ARGENTINE COW-BIRD gI 
the entrance, into which she peers curiously, and 
when about to enter starting back, as if scared at 
the obscurity within. But after retiring a little space 
she will return again and again, as if fascinated with 
the comfort and security of such an abode. It is 
amusing to see how pertinaciously they hang about 
the ovens of the Oven-birds, apparently determined 
to take possession of them, flying back after a hundred 
repulses, and yet not entering them even when they 
have the opportunity. Sometimes one is seen follow- 
ing a Wren or a Swallow to its nest beneath the eaves, 
and then clinging to the wall beneath the hole into 
which it disappeared. 
I could fill many pages with instances of this habit 
of M. bonariensis, which, useless though it be, is as 
strong an affection as the bird possesses. That it is 
a recurrence to a long disused habit I can scarcely 
doubt ; at least to no other cause that I can imagine 
can it be attributed; and besides it seems to me 
that if M. bonariensis, when once a nest-builder, had 
acquired the semi-parasitical habit of breeding in 
domed nests of other birds, such a habit might 
conduce to the formation of the instinct which 
it now possesses. I may mention that twice I 
have seen birds of this species attempting to 
build nests, and that on both occasions they failed 
to complete the work. So universal is the nest- 
making instinct that one might safely say that the 
M. bonariensis once possessed it, and that in the 
cases I have mentioned it was a recurrence, too 
weak to be efficient, to the ancestral habit. 
