niger_ is larger and of a much redder tint; the more prominent spots also are larger, the subdued grey being quite similar in both. If we were to judge from habits alone, the specific difference between these two species of Molothrus might well be doubted; they seem closely to resemble each other in general habits,—in manner of feeding,—in associating in the same flock with other birds, and even in such peculiarities as often alighting on the backs of cattle. The _M. pecoris_, like the _M. niger_, utters strange noises, which Wilson[16] describes “as a low spluttering note as if proceeding from the belly.” It appears to me very interesting thus to find so close an agreement in structure, and in habits, between allied species coming from opposite parts of a great continent. Mr. Swainson[17] has remarked that with the exception of the _Molothrus_, the cuckoos are the only birds which can be called truly parasitical; namely, such as “fasten themselves, as it were, on another living animal, whose animal heat brings their young into life, whose food they alone live upon, and whose death would cause theirs during the period of infancy.” It is very remarkable, that the cuckoos and the molothri, although opposed to each other in almost every habit, should agree in this strange one of their parasitical propagation: the habit moreover is not universal in the species of either tribe. The Molothrus, like our starling, is eminently sociable, and lives on the open plains without art or disguise:[18] the cuckoo, as every one knows, is a singularly shy bird; it frequents the most retired thickets, and feeds on fruit and caterpillars.[19] AMBLYRAMPHUS RUBER. _G. R. Gray._ Oriolus ruber, _Gmel._ Amblyramphus bicolor, _Leach._ Sturnus pyrrhocephalus, _Licht._ Sturnella rubra, _Vieill._ Leistes erythrocephala, _Swains._ Class. Birds. This bird frequented marshy places in the neighbourhood of Maldonado, but it was not common there. It is more solitary than the following allied species; I have, however, seen it in a flock. Seated on a twig, with its beak widely open, it often makes a shrill, but plaintive and agreeable cry, which is sometimes single and sometimes reiterated. Its flight is heavy. The young have their heads and thighs merely mottled with scarlet. STURNELLA MILITARIS. _Vieill._ Sturnus militaris, _Gmel._ Etourneau des terres Magellanique, Pl. enl. 113. I met with specimens of this bird on the east coast of the continent from the Falkland Islands to 31° S., and on the western coast from the Strait of Magellan to Lima, a space of forty degrees of latitude. FAMILY.—TROCHILIDÆ. 1. TROCHILUS FLAVIFRONS. Monte Video.—November. Not abundant. 2. TROCHILUS FORFICATUS. _Lath._