1874.] MOLOTHRI OF BUENOS AYRES. 161 



bird that laid the additional five eggs before had gone away on find- 

 ing herself robbed. The birds still remained ; and when I had reason 

 to believe that they had commenced to lay the fourth time, I visited 

 the nest and found two eggs in it ; I left them, and returned in three 

 days expecting to find five eggs, but found seven ! Certainly more 

 than one female had on this occasion laid in the nest. I have in- 

 vented several theories to account for the additional eggs ; but they 

 are not satisfactory, and it is useless to record conjectures. After 

 taking the last eggs, the Bay-wings left ; and though the Molothri ru- 

 foaxillares continued to make rather frequent visits to the nest, to my 

 great disappointment they did not lay in it. Last summer (18/1-2) I 

 found one nest of the Bay-wings ; it was deep and nicely made of long 

 dry grass and fibrous roots. All the other pairs I observed bred in 

 nests of other birds, most of them in Lenateros' nests. This summer 

 (1872-73) all the pairs of Bay-wings I have observed have laid in 

 the nests taken from other birds. 



VI. Habits of Molothrus rufoaxillaris. — This species is by no 

 means rare, though not so abundant as the others ; probably its close 

 resemblance to the If. bonariensis kept it so long unknown to orni- 

 thologists. Like the 1£ . badius, it remains with us the whole year. 

 The M. rufoaxillaris is never seen alone ; nor are they strictly 

 gregarious, but in winter go in parties never exceeding five or six in 

 number. One of its most noteworthy traits is an exaggerated hurry 

 and bustle it throws into all its movements. When passing from one 

 branch to another it goes by a series of violent jerks, smiting its 

 wings loudly together ; and when a party of them return from the 

 fields they rush wildly and screaming to the trees, as if pursued by a 

 Falcon. Their language is as abrupt as are their motions. They are 

 not singing birds ; but the male sometimes, though rarely, attempts a 

 song, and utters, with considerable effort, a few brief and unmelodious 

 notes. The chirp with which he invites his mate to fly has the sound 

 of a loud aud smartly given kiss. His warning or alarm note when 

 approached in the breeding-season has a soft and pleasing sound ; it 

 is his only mellow expression. This most common as well as re- 

 markable vocal performance is a cry beginning with a hollow-sound- 

 ing internal note, and swelling into a sharp metallic ring ; it is uttered 

 with tail and wings spread and depressed, the whole plumage raised 

 like that of a strutting turkey-cock, whilst the bird hops briskly up 

 and down on its perch as if dancing. From its manner of puffing 

 itself out, and from the peculiar nature of the sound it produces, I 

 believe that, like the Pigeon and other species, it has the faculty of 

 filling its crop with air, using it as a " chamber of resonance." The 

 note I have described is quickly and invariably followed by a scream, 

 harsh and impetuous, uttered by the female, though both notes always 

 sound as if proceeding from one bird. Frequently, when the flock is 

 on the wing, these screaming notes without the prelude are uttered 

 by all the birds in concert. The plumage of this species has a strong 

 musky smell ; the oesophagus is remarkably wide. It lives almost 

 exclusively on seed ; but sometimes a large caterpillar or spider is 

 also found in the stomach. 



