BIEDS. 61 



superior to that of any other bird which I heard in South America ; and they are 

 almost the only ones which formally perch themselves on an elevated twig for the 

 purpose of singing. They sing only during the spring of the year. I may here 

 mention, as a curious instance of the fine shades of difference in habits between 

 very closely allied species, that when I first saw the M. Patagonicus, I concluded 

 from habits alone that it was different from M. Orpheus. But having afterwards 

 procured a specimen of the former, and comparing the two without particular 

 care, they appeared so very similar that I changed my opinion. Mr. Gould, 

 however, immediately upon seeing them (and he did not then know that M. 

 D'Orbigny had described them as different) pronounced that they were distinct 

 species ; a conclusion in conformity with the trifling difference of habit and 

 geographical range, of which he was not at the time aware. 



3. Mimus Thenca. G. R. Gray. 



Turdus Thenca. Mol. 



Orpheus Thenca. B'Orb. Voy. de l'Amer. Mer. Orn. p. 209, pi. f. 3. 



This species seems to be confined to the coast of the Pacific, west of the Cor- 

 dillera, where it replaces the M. Orpheus, and M. Patagonicus of the Atlantic side 

 of the continent. Its southern limit is the neighbourhood of Concepcion, (lat. 

 37° S.) where the country changes from thick forests to an open land. The 

 Thenca, (which is the name of this species, in the language of the Aboriginal 

 Indians,) is common in central and northern Chile, and is likewise found (I 

 believe the same species) near Lima, (lat. 12°) on the coast of Peru. The habits 

 of the Thenca are similar, as far as I could perceive, to those of the M. Patago- 

 nicus. I observed many individuals, which had their heads stained yellow from 

 the pollen of some flower, into which they bury their heads, probably for the 

 sake of the small beetles concealed there. Molina describes the nest of 

 the Thenca, as having a long passage, but I was assured by the country 

 people, that this nest belonged to the Synallaxis cegithaloides, and that the 

 Thenca makes a simple nest, built externally of small prickly branches of the 

 mimosa. 



