78 BIRDS OF LS PLATA 
is not infrequently abandoned on account of these 
premature eggs. Some species, however, do not 
forsake their nests; and though they do not throw 
the parasitical eggs out, which would seem the 
simplest plan, they have discovered how to get rid 
of them, and so save themselves the labour of making 
a fresh nest. Their method is to add a new deep 
lining, under which the strange eggs are buried out 
of sight and give no more trouble. The Sisopygis 
icterophrys—a common Tyrant-bird in Buenos Ayres 
—frequently has recourse to this expedient; and 
the nest it makes being rather shallow, the layer of 
fresh material, under which the strange eggs are 
buried, is built upwards above the rim of the original 
nest; so that this supplementary nest is like one 
saucer placed within another, and the observer is 
generally able to tell from the thickness of the whole 
structure whether any parasitical eggs have been 
entombed in it or not. Finding a very thick nest one 
day, containing two half-fledged young birds besides 
three addled eggs, I opened it, removing the upper 
portion or additional nest intact, and discovered 
beneath it three buried Molothrus eggs, their shells 
encrusted with dirt and glued together with broken- 
egg matter spilt over them. In trying to get them out 
without pulling the nest to pieces I broke them all ; 
two were quite rotten, but the third contained a 
living embryo, ready to be hatched, and very lively 
and hungry when I took it in my hand. The young 
Tyrant-birds were about a fortnight old, and as they 
hatch out only about twenty days after the parent- 
