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Mr. Darwin then read some notes upon the Rhea Americana, and upon the newly described species,¹ but principally referring to the former.

This bird abounds over the plains of Northern Patagonia and the United Provinces of La Plata; and though fleet in its paces and shy in its nature, it yet falls an easy prey to the hunters, who confound it by approaching on horseback in a semicircle. When pursued it generally prefers running against the wind, expanding its wings to the full extent. It is not generally known that the Rhea is in the habit of swimming, but on two occasions Mr. Darwin witnessed their

¹ Named by Gould Rhea Darwinii, however it had already been named Rhea pennata by Orbigny [1834]-47, vol. 2, p. 67 note 2 [now called Pterocnemia pennata (Orbigny, 1834)]. This report of CD's notes followed Gould's original description Gould 1837a.

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crossing the Santa Cruz river, where its course was about 400 yards wide and the stream rapid. They make but slow progress, their necks are extended slightly forwards, but little of the body appears above water. At Bahia Blanca, in the months of October and September, an extraordinary number of eggs are found all over the country. The eggs either lie scattered about, or are collected together in a shallow excavation or nest; in the former case they are never hatched, and are termed by the Spaniards Huachos. The Gauchos unanimously affirm that the male bird alone hatches the eggs, and for some time afterwards accompanies the young. Mr. Darwin does not doubt the accuracy of this fact, and states that the cock bird sits so closely that he has almost ridden over one in the nest. Mr. Darwin has also been positively informed that several females lay in one nest, and although the fact at first appears strange, he considers the cause sufficiently obvious, for as the number of eggs varies from 20 to 50, and, according to Azara, even 70 or 80, if each hen were obliged to hatch her own before the last was laid, the first probably would have been addled; but if each laid a few eggs at successive periods in different nests, and several hens, as is stated to be the case, combine together, then the eggs in one collection would be nearly of the same age. Mr. Burchell¹ mentions that in Africa two females are believed to lay in one nest.

Mr. Darwin then proceeds to notice the other species of Rhea, which he first heard described by the Gauchos, at River Negro, in Northern Patagonia, as a very rare bird, under the name of Avestruz Petise. The eggs were smaller than those of the common Rhea, of more elongated form, and with a tinge of pale blue. This species is tolerably abundant about a degree and a half south of the Rio Negro, and the specimen presented to the Society was shot by Mr. Martens² at Port Desire in Patagonia, (in latitude 48). It does not expand its wings when running at full speed, and Mr. Darwin learned from a Patagonian Indian that the nest contains fifteen eggs, which are deposited by more than one female. It is stated in conclusion that the Rhea Americana inhabits the country of La Plata as far as little south of the Rio Negro, in lat. 41°, and that the Petise takes its place in Southern Patagonia.

¹ William John Burchell (1781-1863), explorer and naturalist. Burchell 1822, vol. 1, p. 280.

² Conrad Martens (1801-1878), draughtsman on the Beagle from 1833-1834.