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Show 548 MR. HUDSON ON THE BIRDS OF BUENOS AYRES. [June 23, (No. VI.) " Buenos Ayres, April 11, 1870. " M Y D E A R SIR,-The Blackbirds, Pajaro negro (Molothrus bonariensis), with characteristic irregularity, often leaving us at the end of March, apparently for good, have again appeared this year in great numbers. When summer is over these birds congregate in vast flocks, and are then seen for many days flying north ; but it is not probable that they migrate to any very great distance. . They pass with a rapid, low, undulating flight, one flock behind the other, their wings producing a soft and agreeable sound. The Blackbirds feed on the ground, following the plough in spring to pick up the worms, and are fond of keeping round cattle in the pasture, frequently alighting on their backs. The song of the male is, when wooing, accompanied hy strange gestures and actions. Swelling and ruffling his feathers like a turkey-cock, and frequently suddenly taking wing and flying directly away from the female, and performing a wide circuit round her in the air, he sings all the time. The song begins with remarkable hollow, internal notes, ending with others loud and clear. The female is homely in appearance in her dull mouse-coloured suit, and has no song hut a low chattering, not often uttered, and always appears very indifferent to the advances of her beautiful glossy partner. In the evening, when they settle on the trees to roost, they sing until it is quite dark. From their great numbers, their singing at such times often sounds like the rushing of a strong wind among the trees. When disturbed on their roost at night the males repeat their song as they take wing ; they also settle on the trees on rainy days to sing, continuing their concert for hours. One of our marsh-Blackbirds, the Chrysomus frontalis, possesses this habit of singing while it is raining ; its song begins with a low mourning note, to which succeeds a long, soft, plaintive whistle; this is followed by others, short and in rapid succession as they rise, growing longer as they sink again, until they die away. This song heard in wet and gloomy weather has an indescribably sweet and melancholy effect. But to return to the common Blackbird ; the most remarkable thing about this bird is its manner of reproduction ; and this would be a very interesting subject of study to the philosophic naturalist. It is well known that, like the European Cuckoo, it deposits its eggs in the nests of other birds. But the Cuckoo lays hut one ee:2* in a nest, and its peculiar habit possesses one thing in common with the instincts of other animals; it is regular and definite, ensures the safety of the young, and, for all that has yet been established to the contrary, is unchangeable as are the laws of matter and force. The instinct of the Blackbird is, on the contrary, unsettled and indefinite and truly a ** monstrosity.' It is as if the true instinct had been partially eradicated or disfigured, so that its traces appear in various modes and degrees of intensity in different individuals-strong enough, though deformed, in some to secure the safety of the young, in others so dim and uncertain as to make reproduction impossible. Had Darwin been well acquainted with the habits of this bird he |