_Description._--Above dull reddish brown, mottled with concealed spots and bars of ochraceous buff; scapulars with an ashy tinge; head more rufous and longitudinally streaked; whitish collar on the hind neck; wings dark brown, banded with rufous; tail dark brown, with about ten rufous bars, and tipped with whitish; cheeks and chin pure white, the latter divided by a dark brown throat-band from the white fore neck; abdomen white, streaked with dark brown: whole length 8·0 inches, wing 3·8, tail 2·9. _Female_ similar, but rather larger. _Hab._ La Plata, Patagonia, and Chili. This diminutive Owl, which barely reaches eight inches in length, and is light brown and grey in colour, was discovered by Captain King in 1827 in the neighbourhood of the Straits of Magellan. I met with it on the Rio Negro in Patagonia, but saw very little of it. It struck me that, like the Burrowing-Owl, it is not very strictly nocturnal, for I observed it in the daytime perched in exposed situations. In 1882 White met with it in Cosquin, in Cordova, and made the following important note on its habits:--"It causes the naturalist much amusement to watch the habits of this pretty little Owl, that, perched perfectly motionless on a branch, utters such a sirenic cry as to attract little birds in great numbers. They are observed to cluster round it, all the while fluttering and in great excitement, charmed by some fascination. After waiting a while the Owl suddenly pounces upon the nearest for its victim." I also observed little birds mobbing it, when it perched in a conspicuous place in the daytime, as they always mob small birds of prey, but was not so fortunate as to hear the "sirenic cry" with which the Cordova bird fascinates its victims. One has heard this yarn of a "sirenic cry" before, of other species, for it is a very common myth. That an Owl should now be fitted with the old melodious cap seems strange; and Mr. White is in error when he says that this habit in our bird "causes the _naturalist_ much amusement." Order VII. ACCIPITRES. Fam. XXXII. FALCONIDÆ, or FALCONS. The diurnal birds of prey of the family Falconidæ found in the Neotropical Region number about 110 species, of which 22 are at present known to occur within the limits of the present work. It is probable, however, that many additional species of this group will be hereafter added to the Argentine list. As is usually the case with the Accipitres, most of the species have an extensive distribution. 292. CIRCUS CINEREUS (Vieill.). (CINEREOUS HARRIER.)