FALCONID^.— POLYBOKUS THAKUS. 59 



portions of the United States. It was first observed by Mr. Audubon in Florida, 

 Avhere it is not of imcommon occurrence, and where it is supposed also occasionally, 

 though rarely, to breed. I am not aware that the Caracara has ever been observed 

 in Alabama, Mississippi, or Louisiana,' although it is quite probable that it may be 

 found not unfrequent in the more southern j)ortions of these States. In Texas, es- 

 pecially on the Rio Grande, it is a quite common bird, as it is also in Mexico and 

 Central America. Throughout South America it is one of the most abundant spe- 

 cies, its geographical range extending even to Cape Horn. Dr. Darwin found the 

 Polyhorus nowhere so common as on the grassy savannas of the La Plata, and says 

 that it is also found on the most desert plains of Patagonia, even to the rocky and 

 barren shores of the Pacific. It occurs also in the West Indies, especially in the 

 island of Cuba, where it is known to breed. The eggs represented in the drawing 

 were obtained and identified by the late Dr. Berlandier of Metamoras, in Northern 

 Mexico, on the Rio Grande. 



It is possible that two distinct species are now confoimded together under the 

 common name of Caracara Eagle. Mr. Cassin informs me that his suspicions have 

 been excited by certain variations in specimens which have fallen under his notice, 

 and Mr. Darwin states that he met with individuals on the plains of Santa Cruz 

 which he and Mr. Gou.ld were almost persuaded to be distinct species. In partial 

 confirmation of this suspicion, I may in this connection refer to the great variations 

 noticeable in the eggs of this vulturine Eagle. These are neither slight nor occa- 

 sional, but are constant, and of so radical a character as to excite the strongest 

 doubts of their belonging to birds of the same species, the differences affecting both 

 their size and their ground color. The eggs from Cuba, so far as I am aware, rep- 

 resent one variety exclusively, those from Brazil the other, while, on the other 

 hand, both varieties were obtained on the Rio Grande by Dr. Berlandier, who as- 

 signed them to a single species, which, in his manuscript notes, he called Totache. 

 In Chile the popular name of this bird is Traro, but its more common title in other 

 portions of South America is Carrancha, 



The Caracara builds a coarse, flat nest, composed of flags, reeds, and grass, usu- 

 ally on the tops of trees, but occasionally, according to Darwin, on a low cliff, or 

 even on a bush. The number of the eggs is rarely, if ever, more than three. Four 

 from the Rio Grande, in my collection, exhibit the following measui-ements : length 

 2^^^^ inches, breadth 1{|; length 2^^, breadth 1{| ; length 2^^^, breadth l^f; length 

 2j\, breadth l^f. These eggs not only present the great and unusual variation 

 in their length of nearly eight per cent (between the two extremes), but very 

 striking and anomalous deviations from uniformity are also noticeable in their 

 ground color and markings. The ground color varies in these specimens from a 

 nearly pure white to a very deep russet, or tan-color, and their markings, though 

 all of sepia-brown, differ greatly in their shades. So far as I may be justified in 

 determining from the few specimens I have seen, the eggs with the light ground are 



1 Since writing this article, I have learned that the Smithsonian Institution possesses specimens from 

 the Gulf coast of Louisiana, and from[_Ne\v Mexico and California. 



