Azara states that several Carranchas, five or six together, will unite in chase of large birds, even such as herons. All these facts show that it is a bird of very versatile habits and considerable ingenuity. I am led to suppose that the young birds of this species sometimes congregate together. On the plains of Santa Cruz (lat. 50° S. in Patagonia), I saw in the month of April, or early autumn, between twenty and thirty Polybori, which I at first thought would form a species distinct from _P. Brasiliensis_. Amongst those I killed, there were some of both sexes; but the ovarium in the hens was only slightly granular. The plumage of the different individuals was nearly similar; and in none appeared like that of an adult bird, although certainly not of a very young one. Having mentioned these circumstances to Mr. Gould, he likewise suspected it would form a new species; but the differences appear so trifling between it and the specimens of young birds in the British Museum and in the Museum of the Zoological Society, and likewise of the figure of a young bird given by Spix, (Avium Species Novæ, vol. i. p. 3.), that I have thought it advisable merely to allude to the circumstance. In my specimen, which is a cock, the head, instead of being of a dark brown, which is the usual character of even very immature birds, is of a pale rusty brown. The bill and cere are less produced than in the adult _P. Brasiliensis_; and the cere is of a brighter colour, than what appears to be usual in the young of this species. In other respects there is such a perfect similarity between them, that I do not hesitate to consider my specimen as a young bird of the _P. Brasiliensis_ in one of its states of change;—and to be subject to great variation of plumage during growth, is known to be a character common to the birds of this sub-family. It may, however, possibly be some variety of the _P. Brasiliensis_, for this bird seems subject to variation: Azara (Voyage dans l’Amérique Méridionale, vol. iii. p. 35.) remarks, “Il y a des individus dont les teintes sont plus faibles, ou d’un brun pâle, avec des taches sur la poitrine, et d’autres qui ont des couleurs plus foncées; j’ai décrit ceux qui tiennent le milieu entre les uns et les autres.” I have myself more than once observed a single very pale coloured bird, in form like the _P. Brasiliensis_, mingled with the other carrion-feeding hawks on the banks of the Plata; and there is now in the British Museum a specimen, which may be considered as partly an albino. Spix, on the other hand, (Avium Species Novæ, p. 3.) has described some specimens from the coast of Brazil, as being remarkable from the darkness of the plumage of their wings. MILVAGO, _Spix_.