1920] Cape Son Antonio, Btionos Ayres. 51 



Hudson, in 'Argentine Ornitliology/ when dealing with 

 the inollusk whicli forms its subsistence, evidently refers to 

 a bivalve which is unknown to rae. The exclusive food of 

 the Courlan in our district is the abundant and large water- 

 snail {Ampullaria canaliculata Lamarck), already mentioned 

 by me as similarly constituting the sole sustenance of a 

 bird of a very different family, namely, the Sociable Marsh- 

 Hawk (Rostrhamus socio bills Vieill.). 



From the beginning of the great flood in the middle of 

 1913, and during all its continuance, the Courlan was 

 extraordinarily abundant. Though not gregarious in the 

 strict sense of the word, certain situations in which the 

 food-supply was evidently particularly favourable seemed to 

 draw large numbers together in grou|)s up to half a score. 

 In a small submerged " durasnillal " between the head- 

 station woods and the Canada i)ropei', I put up some fifty or 

 sixty one day in March of 1913. These "rose like a flock 

 of Ibises, but sombre and uncouth in appearance; about 

 twenty of them perched on the very tops of adjacent Tala 

 trees, where tliey looked if possible even more ungainly and 

 weird than when on the wing." Only a week previously, 

 when riding out at sunrise near the above locality, I found 

 about thirty Courlans still roosting in a clump of willow 

 trees at a bridge, in company with a large number of the 

 Dark Night-Heron (Nycticora.v obscurus Bp.) and the 

 Sociable Marsh-Hawk {Rostrhamus sociabilis Vieill.); the 

 first-named slowly abandoned their perches and flew down 

 the Canada, whilst their associates scattered generally iu a 

 similar leisurely manner. The same afternoon, returning 

 home lower down, I put my horse through the so-called 

 "Estancia pass" (myself atop the '^ Chaja's " nest), and 

 found a Courlan's nest amongst the rushes at the very edge 

 of the pass, midway. The young, jet black, were hatching 

 out, and as I endeavoured to steady my horse for a moment 

 they proceeded at once to scram l)le over the edge of the nest, 

 which was low down in the water. The date, 2i Fcbruarv, 

 seemed very late ; corresponding to the end of summer. The 

 perchiug-habit of the Courlan is. so far as our district is 



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