14 Mr. E. Gibson on the Ornithology of 
sparse. The slope of the passage I have always found to be 
correctly calculated, so as not to disconcert the bird by a 
possible emergence into the open air should the ground fall 
away behind the burrow. The bird sits close, and may often 
be excavated with the nest. 
Three is the general number of eggs laid ; and I only once 
recollect taking a nest with four. ‘The colour is white. 
Twenty-four specimens give an average measurement of #5 
x 28. The variation in size is pretty considerable. 
Hirundo leucorrhoa (Vieill.) not unfrequently occupies and 
breeds in a deserted nest of Geositia cunicularia. 
20. MoLoTHRUS BONARIENSIS. 
A species but too common, as my oological experiences have 
often proved. 
- One sees it everywhere—in the plains, the woods, and the 
swamps. It is one of the most regular and abundant fre- 
quenters of the patios or courtyards, where the beautiful 
glossy black plumage of the male reflects the sunlight in all 
the metallic tints of blue, green, purple, and violet, as it runs 
about within a few yards of the observer, or gives utterance 
to its note (a peculiar gurgle, as if it had water in its throat). 
It has the Starling-like habit of craning up its head to observe 
any distant or suspicious object, and, also like that bird, may 
often be seen perched on the backs of the cattle or sheep. 
At times, generally in the winter months, as far as some 
insufficient notes bear me out, it gathers into flocks; and 
these flocks seem to consist principally of males. However, 
it is at all times semigregarious in its habits. 
Though it lays in the nests of a considerable number of 
other birds, the Sparrow (Zonotrichia pileata, Bodd.) is the 
most highly distinguished of all in that respect, and is the 
only one I have ever seen feeding the young bird. ‘The latter 
follows its foster-mother for some time after leaving the nest, 
and, with open gape, may be seen perpetually clamouring for 
food, which the unfortunate little Sparrow must find hard to 
supply in sufficient quantity. 
