Cape San Antonio, Buenos Ayres. 15 
I may here insert the following note, dated end of Feb- 
ruary :—‘‘ Saw what I took to be two young of this species, 
perched on the back of a sheep. Both were in the usual im- 
mature grey plumage; but in addition one had a dark patch 
on the back of head, another on neck, and a third on the 
back, embracing part of the wings.” I have never since seen 
a specimen with similar markings, the type being, as already 
noted, of a uniform grey in the young. 
Independent of its parasitical habits, it causes great de- 
struction among the smaller birds by puncturing and sucking 
their eggs on every possible occasion. Bitter experience has 
taught me the folly of ever leaving any nest of eggs till the 
full clutch should be laid ; for some of these black thieves are 
sure to be watching one’s actions, with a result that may be 
imagined but is too painful to describe. 
The food is very varied, as might be inferred from the 
general distribution of the bird; and nothing, either of an 
animal or vegetable nature, seems to come amiss to it. In 
company with Amblyrhamphus holosericeus, it takes a too 
kind interest in the maize-patch, and also frequently asso- 
ciates with Pseudoleistes virescens, on the principle, I suppose, 
that “ birds of a feather flock together ”—P. virescens being 
semiparasitical, worse luck to it ! 
Breeding-Notes.—M. bonariensis is parasitical on the fol- 
lowing birds :—the Sparrow (Zonotrichia pileata), Wren 
(Troglodytes furvus), Red Oven-bird (Furnarius rufus), Pseu- 
doleistes virescens, Thrush (Turdus rufiventris), Chrysomi- 
tris magellanica, Leptasthenura egithaloides, Progne tapera 
Lichenops perspicillata, Scissor-Bird (Milvulus tyrannus— 
ten species in all, though this list may doubtless be easily 
added to. 
My specimens were mostly taken in one season ; so that I 
can only state approximately the duration of the breeding- 
season—namely, from 20th October to 10th January. It is 
likely, however, that it begins to breed earlier. 
Four was the largest number taken out of one nest (that 
of a Wren) ; and these were in various stages of incubation. 
