78 BIRDS OF LA 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- 



