444 LIFE HISTORIES OP NORTH AMERICAN BIRDS. 



tion going south in winter. Those that remain gather in large flocks with the 

 Long-tailed Grackles, common Cowbirds, and Brewer's, Red-winged, and Yellow- 

 headed Blackbirds; they become very tame, and the abundance of food about 

 the picket lines attracts them for miles around. Callothrus robustus is readily 

 distinguishable in these mixed gatherings from the other species by its blood-red 

 iris and its peculiar top-heavy appearance, caused by its habit of puffing out the 

 feathers of the head and neck. This habit is most marked during the breeding 

 season and in the male, but is seen throughout the year. 



"About the middle of April the common Cowbird and Brewei-'s and the 

 Yellow-headed Blackbirds leave for the north; the Long-tailed Grackles have 

 formed their colonies in favorite clumps of mesquite trees; the Redwings that 

 remain to breed have selected sites for their nests; the Dwarf Cowbirds, Molothrus 

 pecoris obscurus, arrive from the south, and Callothrus robustus gather in flocks by 

 themselves and wait for their victims to build. The males have now a variety 

 of notes, somewhat resembling those of the common Cowbird, Molothrus pecoris, 

 but more harsh. During the day they scatter over the surrounding country in 

 little companies of one or two females and half a dozen males, returning at 

 nightfall to the vicinity of the picket lines. While the females are feeding or 

 resting in the shade of a bush the males are eagerly paying their addresses by 

 puffing out their feathers, as above noted, strutting up and down, and nodding 

 and bowing in a very odd manner. Every now and then one of the males rises 

 in the air, and, poising himself two or three feet above the female, flutters for a 

 minute or two, following her if she moves away, and then descends to resume 

 his puffing and bowing. This habit of fluttering in the air was what first 

 attracted my attention to the species. In other respects their habits seem to be 

 like those of the eastern Cowbird (Molothrus pecoris). 



"My first egg of Callothrus robustus was taken on May 14, 1876, in a Car- 

 dinal's nest. A few days before this a soldier brought me a similar egg, saying 

 he found it in a Scissors-tail's (Milvulus) nest. Not recognizing it at the time, I 

 paid little attention to him, and did not keep the egg. 1 soon found several 

 others, and have taken in all twenty-two specimens the past season. All but two 

 of these were found in nests of the Bullock's, Hooded, and Orchard Orioles. It 

 is a curious fact that although Yellow-breasted Chats and Red-winged Black- 

 birds breed abundantly in places most frequented by these Cowbirds, I have but 

 once found the latter's egg in a Chat's nest, and never in a Redwing's, though I 

 have looked in very many of them. Perhaps they feel that the line should be 

 drawn somewhere, and select their cousins, the Blackbirds, as coming within it. 

 The Dwarf Cowbirds are not troubled by this scruple, however. Several of 

 these parasitic eggs were found under interesting conditions. On six occasions 

 I have found an egg of both Cowbirds in the same nest. In four of these there 

 were eggs of the rightful owner,^ who was sitting. In the other two the Cow- 

 bird's eggs were alone in the nests, which were deserted. But I have known the 



'It would be interesting to know what would liave become of the three species In one nest, and had the 

 latter been near the fort, where I could have visited them daily, I should not have taken the eggs. It is 

 probable, however, that Callothrus rohuatua would have disposed of the young Dwarf Cowbird as easily as 

 of the young Orioles. 



