36 Mr. E. Gibson on the Ornithology of [Ibis, 



I have not yet observed it on the open plains, as frequently 

 occurs with Zenaida maculata. 



Only half-a-dozen nests have actually come under my 

 notice, but some o£ them present special points of interest. 

 For example, the period ranges from 23 August, when, in 

 bitter cold weather, I was amazed to find a bird sitting on 

 two eggs, up to the end of December. Further, I have 

 observed fully-tledged young, not long from their nursery, 

 on such far-apart dates as 21 November and 8 February. 

 My first nest was not obtained until 1895, or twenty-one 

 years after I took up residence at the Yngleses ; and the 

 remainder at long intervals up to 1916, when I myself was 

 only a visitor. These nests divide themselves into two 

 distinct forms — either a ^esf feathers are placed upon an old 

 nest of, say, the Mocking-bird [Mimus modulator Gould), or 

 the Guira Cuckoo {Guira piririyua Vieill.) in a thick 

 " Quebrachillo '' or " Coronillo " tree, six or eight feet from 

 the ground; or, a special structure in a small ^'Tala" or 

 other tree with no attempt at concealment, and at a similar 

 height. I transcribe the following notes regardiug one of 

 these: — ^'Placed in the fork of a stunted and isolated 

 Tala tree on the confines of a wood. So like in appearance to 

 that of the Black-headed Siskin (Chrysomitris icterica Licht.) 

 and so unlike a Pigeon\«, that, in spite of the bird flying 

 off, 1 could hardly believe in the fact until I saw the eggs. 

 The nest was small, rather deep, built of rootlets and fine dry 

 grass, and copiously lined with feathers of the parent birds. 

 By an odd coincidence, its discovery was due to my firing at 

 the moment at a fine specimen of its big congener, Columba 

 /jfcflrwo, ' the first seen for a long time.' ^' The preceding 

 incident took place in 1901, and the concluding remark in 

 my journal would seem to be a prophetic anticipation of 

 the transposition of the two species to which I have drawn 

 attention in the present paper, the spread of Columbula 

 picui and the decrease in Columba picazuro. 



The pure white and oval eggs show very little variation in 

 size and shape, averaging 24 x 17 mm. 



