108 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



with the usual black kind, there were generally a few dull brown coloured ones, 

 {Icterus sericeus of Licht.) which I presume are the young. Azara states that 

 the brown-coloured birds are smaller than the black glossy ones, and that they 

 sometimes form one-tenth of the whole number in a flock. In the single specimen 

 which I brought home, the size, with the exception of the length of the wing, is 

 only a very little less. Sonnini, in his notes to Azara, considers the brown birds 

 as the females ; I can, however, scarcely believe that so obvious a solution of the 

 difficulty could have escaped so accurate an observer as Azara, These birds 

 in La Plata often may be seen standing on the back of a cow or horse. While 

 perched on a hedge, and pluming themselves in the sun, they sometimes attempt 

 to sing or rather to hiss : the noise is very peculiar ; it resembles that of bubbles 

 of air passing rapidly from a small orifice under water, so as to produce an acute 

 sound. Azara states that this bird, like the cuckoo, deposits its eggs in other 

 birds' nests. I was several times told by the country people, that there was some 

 bird which had this habit; and my assistant in collecting, who is a very accurate 

 person, found in the nest of the Zonotrichia i-uJicollis (a bird which occupies in 

 the ornithology of S. America the place of the common sparrow of Europe), 

 one egg larger than the others, and of a different colour and shape. This 

 egg is rather less than that of the missel-thrush, being -93 of an inch in 

 length, and '78 in breadth ; it is of a bulky form, thick in the middle. The 

 ground colour is a pale pinkish-white, with irregular spots and blotches of a 

 bright reddish-brown, and others less distinct of a greyish hue. This species is 

 evidently a very close analogue of the 31. pecoris of North America, from which, 

 however it may at once be distinguished by the absence of the glossy brown on 

 the head, neck, and upper breast, — by the metallic blueness of its plumage in 

 the place of a green tinge, and by its somewhat greater size in all its proportions. 

 The young or brown-coloured specimens of these Molothri resemble each other 

 more closely ; that of the M. pecoris is of a lighter brown, especially under the 

 throat, and the small feathers on its breast and abdomen have each an obscure 

 dark central streak. The eggs of the Molothri, although having the same 

 general character, differ considerably ; that of the M. pecoris being smaller 

 and less swollen in the middle ; it is -85 of an inch in length, and '78 in breadth. 

 Its colour cannot be better described than in the words of Dr. Richardson* — it is 

 " of a greenish white, with rather small crowded and confluent irregular spots of 

 pale liver-brown, intermixed with others of subdued purplish grey." From this 



• Fauna Borealis, Birds, p. 278. Dr. Richardson states that the egg is only seven lines and a half in length. 

 I presume the measure of eight lines, instead of twelve to the inch, must in this case have been used. I am 

 much indebted to the kindness of Mr. Yarrell for lending me an egg of the Mohthrus pecoris, forming part of a 

 collection of North American eggs in his possession. 



