ARGENTINE COW-BIRD 73 



where they are feeding seems carpeted with black, 

 and the trees when they alight appear to have a black 

 foliage. At such times one wonders that many small 

 species on which they are parasites do not become 

 extinct by means of their pernicious habit. In 

 Buenos Ayres, where they are most numerous, they 

 have a migration, which is only partial however. It 

 is noticeable chiefly in the autumn, and varies greatly 

 in different years. In some seasons it is very marked, 

 when for many days in February and March the 

 birds are seen travelling northwards, flock succeeding 

 flock all day long, passing by with a swift, low, un- 

 dulating flight, their wings producing a soft musical 

 sound; and this humming flight of the migrating 

 Cow-birds is as familiar to everyone acquainted with 

 nature in Buenos Ayres as the whistling of the wind 

 or the distant lowing of cattle. 



The procreant instinct of this Molothrus has always 

 seemed so important to me for many reasons that I 

 have paid a great deal of attention to it ; and the 

 facts, or at all events the most salient of them, which 

 I have collected during several years of observation, 

 I propose to append here, classified under different 

 headings so as to avoid confusion and to make it 

 easy for other observers to see at a glance just how 

 much I have learnt. 



Though I have been familiar with this species from 

 childhood, when I used to hunt every day for their 

 wasted eggs on the broad, clean walks of the planta- 

 tion, and removed them in pity from the nests of 

 little birds where I found them, I have never ceased 



