The Chopi, which is said to be quite common in Paraguay, is only found in the north-eastern part of the Argentine Republic, consequently I have never seen it, except as a cage-bird; nor is there anything about it in the notes of recent collectors and travellers who have visited the upper waters of the Plata. This is, however, not to be regretted, since Azara gave a very full and spirited account of this species in his 'Apuntamientos;' although it certainly does seem strange that the Chopi should have had two careful observers of its habits fully a century ago, namely, Azara and his friend and fellow-naturalist the priest Noseda, and not one since. Evidently Azara was very familiar with this bird, for he describes it lovingly and at great length, his history of it being one of the most charming things in his work. According to him the Chopi is a highly sagacious bird, and although a frequent visitor to courtyards and verandahs of houses in Paraguay, too shy and suspicious to be caught with snares. It has a strong and easy flight, and readily attacks any large bird passing near, following it persistently in the air, or, pouncing down, fastens itself on its enemy's back. If the Caracara Eagle (_Polyborus_) alights in order to shake off its persecutor, the Chopi perches at a distance of a few feet, where it assumes an indifferent manner; but no sooner does the Caracara allow its attention to wander from its adversary, then it is again subjected to fresh insult. These attacks on so large and powerful a species may be regarded as mere impertinences, but by practising them the Chopi is soon able to rid himself of the presence of any unwelcome bird. From a long distance he recognizes an enemy, by its figure, or even its shadow, and warns all birds of the coming danger with a loud whistle, which at once sends them into hiding, while the Chopi goes bravely out to the encounter; and the result is invariably a victorious song on his part, beginning with the sound of his own name, and running through a variety of whistled notes. He also sings well in captivity and when his mate is incubating; and his voice is first heard welcoming the dawn from the eaves and tiled roofs of houses where he roosts. The pairing-season is in November; and, Noseda adds, the breeding-place is a hole in a bank, or tree-trunks, or in a wall under the eaves, and occasionally the nest is made in the small branches of an orange or other close-leafed tree, and is built of sticks and straws carelessly disposed, with a few feathers for lining. The eggs are four, and white.