Nov., 1914 
BREEDING OF THE BRONZED COWBIRD IN ARIZONA 
257 
male are seen with them. They are quite tame and get in the shade of a shed 
and eat watermelon every day. 
When the Bullock Oriole began breeding I went to work to examine all 
the nests I could find. I looked into twenty-eight but no alien eggs were 
found. Then the Hooded Orioles began nesting, and while they seem fairly 
numerous, comparatively few nests are seen and most of them hard to reach. 
June 28 I climbed to a nest of the Hooded Oriole about twenty feet from 
the ground in a big cottonwood tree. The nest could not be reached, but get- 
ting directly above it I saw a greenish white egg, and knew the long looked 
for was found. I used a pocket knife vigorously, cut the big branch off and 
secured the nest. In it were two eggs of the Bronzed Cowbird and four of the 
Dwarf Cowbird {Moloilirus ater obscurus). The nest was typical of the spe- 
cies, and made of fiber from the Washington fan palm (see fig. 73). This 
was at Sacaton, on the south side of the Gila Kiver. Both eggs of the Bronzed 
Cowbird had holes picked in them, one showing a little incubation, while the 
other was nearly fresh. Of the Dwarf Cowbirds’ eggs, three were slightly in- 
cubated, and the fourth fresh. What became of the oriole’s eggs is a problem, 
as is also the cause of the holes in the Bronzed Cowbirds’ eggs. My opinion 
is that the Dwarf Cowbird that deposited the last egg saw the nest was too full 
of alien eggs, and so picked holes in those of the other species. If such be the 
case it would explain why the Bronzed Cowbird does not increase faster, for 
the Dwarf is very numerous here. As nearly as I can estimate the number of 
the former species they remain about the same as w>’hen I first saw them five 
years ago. If the oriole picked the holes she showed rank favoritism in saving 
the Dwarf eggs. Evidently her patience was exhausted, for the eggs were cold 
when found, and the nest apparently deserted. 
At Santan, July 7, I found a Hooded Oriole’s nest with four of her own 
eggs and one of the Bronzed Cowbird. The nest was seventeen feet up in a 
cottonwood, and built of grass. Incubation was advanced, and one of the 
Oriole eggs was infertile. Another Hooded Oriole’s nest found the same day 
had three Oriole eggs and one Dwarf Cowbird egg, so the Dwarfs evidently use 
the Hooded Oriole frequently as host, though I have never found them in 
Bullock Oriole nests. July 11, not far from the nest with the one Bronzed 
Cowbird egg, I found another nest of the Hooded Oriole with two legitimate 
eggs and two of the Bronzed Cowbird, incubation begun. This nest was in a 
cottonwood tree about fourteen feet from the ground, and built of grass with 
some horse hair lining (see fig. 74). Two other Hooded Orioles ’s nests exam- 
ined this season contained only the owners’ eggs. 
A few notes on the actions of these birds as observed here may prove of 
interest. With few exceptions they show no indications of being paired, as 
do most birds. They are seen singly or in twos or threes of either sex. One 
day there were four males eating watermelon in the back yard near the door, 
and two females were out in the barnyard by themselves. Two males have 
been together in the school grounds much of the time, and nearly always when 
females are seen they are by themselves. It is not strange that they seek soli- 
tude, as the males appear so amatory as to be a nuisance. The courtship antics 
are interesting. A male will approach to within three feet of his partner, fluff 
out his feathers, stand up straight and begin to flutter his wings. He increases 
the speed and violence of the fluttering till he appears in a perfect frenzy, then 
suddenly springs into the air from three to six feet and slowly descends, body 
perpendicular, beak thrust against breast and tail thrust forward under the 
