1832-3. ORNITHOLOGY. 61 



with other birds. Several may often 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 resem- 

 bles that of bubbles of air passing rapidly from a smaU 

 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 with this habit ; and my 

 assistant in collecting, who is a very accurate person, found 

 a nest of the sparrow* of the country, with one egg in it 

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

 Mr. Swainsonf has remarked that with the exception of the 

 Molothrus pecoris, the cuckoos are the only birds which can 

 be called truly parasitical ; namely, such as '' fasten them- 

 selves, as it were, on another living animal, whose animal 

 heat brings their young into Ufe, whose food they alone live 

 upon, and whose death would cause theirs during the period 

 of infancy.^' The Molothrus pecoris is a North-American 

 bird, and is closely allied in general habits, even in such 

 pecidiarities as standing on the backs of cattle (as its name 

 implies), and in appearance, with the species from the plains 

 of La Plata ; it only differs in being rather smaller and of a 

 different colour, yet the two birds would be considered by 

 every naturahst as distinct species. It is very interesting to 

 see so close an agreement in structure, and in habits, be- 

 tween allied species coming from opposite parts of a great 

 continent. It is also very remarkable, that the cuckoos and 

 the molothri, although opposed to each other in almost 

 every habit, should agree in the one strange one of their 

 parasitical propagation. The molothrus, like our starling, is 



* A Zonotrichia ; — the chingolo of Azara. The egg is rathe-r less than 

 that of the missel-thrush ; it is of a nearly globular form, but with one end 

 rather smaller than the other. The ground colour is a pale pinkish- 

 white, with irregular spots and blotches of a pinkish brown, and others 

 less distinct of a grayish hue. The egg is now in the museum of the 

 Zoological Society. 



t Magazine of Zoology and Botany, vol. i., p. 217. 



