The flight of these birds is swift and rushing; in mid air they have a habit of suddenly deviating from the straight line of their course, making a sharp doubling, and then pursuing the same direction as before. They go in flocks, usually above the trees, and utter harsh screams as they fly. The sexes are precisely alike in plumage. BLACK-BILLED PARROT.[76] _Psittacus agilis._ _Psittacus agilis_, +Gmel.+—Le Vaill. Perr. 105. ? _Psittacus æstivus_, var. α. +Lath.+ Syn. ? ” ” var. δ. Ibid. [76] Length 13¹⁄₄ inches, expanse 20¹⁄₄, flexure 6⁴⁄₁₀, tail 3¹⁄₄, rictus ⁸⁄₁₀, tarsus ⁹⁄₁₀, middle toe 1²⁄₁₀. Irides dark hazel: cere blackish ash-colour. All the Parrots are gregarious, cunning, watchful, noisy, mischievous; and thus are like the Monkeys. This and the following species are so much alike in manners and general appearance, that a description of one applies nearly to the other. Flocks varying from half-a-dozen to twenty or thirty, fly hither and thither over the forest, screeching as they go, and all alight together on some tree covered with berries. Here they feast, but with caution; on a slight alarm one screams, and the whole flock is on the wing, vociferous if not musical; and brilliant if not beautiful; particularly when the sun shines on their green backs and crimsoned wings. They generally prefer lofty trees, except when, in June, the ripe yellow plantain tempts them to descend, or when the black berry shines upon the pimento. Of the latter, the flocks devour an immense quantity, and the former they destroy by cutting it to pieces with their powerful beaks, to get at the small seeds.