67 [Vol. xliii. 



Argentine Cowbird to approach or enter the nest, which is 

 generally an appropriated one — often of previous seasons — 

 of the Firewood-Gatherer (^Anumbius acuticaudatus) or 

 Common English House-Sparrow [Passer domesticus) . There 

 were only two pairs of Bay-winged Cowbird and one of 

 Screaming Cowbird occupying the very limited area of 

 small, recently planted trees surrounding the Administration 

 House at "Los Alfalfares/' so tliat it was a very easy 

 matter to keep all the birds under the closest and most 

 accurjite observation. Incidentally the two females of the 

 two pairs of Bay- wings laid, respectively, the two contrasting 

 types of eggs described by Mr. Hudson in 'Argentine 

 Ornithology,'' vol. i. pp. 92, 97, and although the eggs of 

 the Screaming Cowbird approximate closely to the ordinary 

 or common brown type (especially referred to by Mr. Hudson, 

 as he was unable to distinguish them one from the other) 

 they practically contrast with the rarer bluish-green type. 

 I only personally collected the eggs of the Screaming Cow- 

 bird from the two nests taken on the 5th December, 1907 — 

 three eggs in the nest of the Bay-wings laying the usual 

 brown type of egg, and one egg in the nest holding the 

 clutch of five eggs of the rare bluish-green type. 



These nests of the Bay-wings were nearly 100 yards apart, 

 and it is worthy of note that the parent Screaming Cowbirds, 

 both male and female, were most solicitous while the eggs 

 were being collected and flew closely around me, exhibiting 

 the same anxiety and concern as that displayed by the 

 Bay-wings themselves. 



The last clutch of eggs containing two of the Screaming 

 Cowbird was collected after my departure by a relative to 

 whom I had shown the nest, and sent to me hy him ; and it 

 is probable that, had a proper search been made, other eggs 

 would have been found in the sixth laying of the other pair 

 of Bay-wings. As will be seen, five sets of eggs were laid 

 in the one season by one pair of Bay-wings and six sets by 

 the other, at intervals of about thirteen days^ a proof of the 

 persistency of this species to procreate its kind when previous 

 efforts have been frustrated. 



