Music and Dancing in Nature. 273
bird, the first bird, on the appearance of its mate flying to join it, begins to emit loud, measured notes, and sometimes a continuous trill, somewhat metallic in sound; but immediately on the other bird striking in this introductory passage is changed to triplets, strongly accented on the first note, in a tempo vivace; while the second bird utters loud single notes in the same time. While thus singing they stand facing each other, necks outstretched and tails expanded, the wings of the first bird vibrating rapidly to the rapid utterance, while those of the second bird beat measured time. The finale consists of three or four notes, uttered by the second bird alone, strong and clear, in an ascending scale, the last very piercing.
In the melodists proper the displays, in a majority of cases, are exclusively vocal, the singer sitting still on his perch. In the Troupials, a family of starling-like birds numbering about one hundred and forty species, there are many that accompany singing with pretty or grotesque antics. The male screaming cow-bird of La Plata, when perched, emits a hollow-sounding internal note that swells at the end into a sharp metallic ring, almost bell-like: this is uttered with wings and tail spread and depressed, the whole plumage being puffed out as in a strutting turkey-cock, while the bird hops briskly up and down on its perch as if dancing. The bell-like note of the male is followed by an impetuous scream from the female, and the dance ends. Another species, the common Argentine cow-bird of La Plata, when courting puffs out his glossy rich violet plumage, and, with wings vibrating, emits a succes-
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274 The Naturalist in La Plata.
sion of deep internal notes, followed by a set song in clear, ringing tones; and then, suddenly taking wing, he flies straight away, close to the surface, fluttering like a moth, and at a distance of twenty to thirty yards turns and flies in a wide circle round the female, singing loudly all the time, hedging her in with melody as it were.
Many songsters in widely different families possess the habit of soaring and falling alternately while singing, and in some cases all the aerial postures and movements, the swift or slow descent, vertical, often, with oscillations, or in a spiral, and sometimes with a succession of smooth oblique lapses, seem to have an admirable correspondence with the changing and falling voice--melody and motion being united in a more intimate and beautiful way than in the most perfect and poetic forms of human dancing.
One of the soaring singers is a small yellow field-finch of La Plata--Sycalis luteola; and this species, like some others, changes the form of its display with the seasons. It lives in immense flocks, and during the cold season it has, like most finches, only aerial pastimes, the birds wheeling about in a cloud, pursuing each other with lively chirpings. In August, when the trees begin to blossom, the flock betakes itself to a plantation, and, sitting on the branches, the birds sing in a concert of innumerable voices, producing a great volume of sound, as of a high wind when heard at a distance. Heard near, it is a great mass of melody; not a confused tangle of musical sounds as when a host of Troupials sing in concert, but the notes, although numberless, seem to flow smoothly and separately, producing an