ARIZONA BLUE-THROATED HUMMINGBIRD 329 



extremes measure 16.8 by 10.0, 15.0 by 10.4, and 13.8 by 9.7 millimeters. 

 Plumages.— I have seen no naked young and no partially fledged 

 nestlings. In the young male the forehead and more or less of the 

 crown are brownish gray, with no green feathers ; the green feathers 

 of ihQ upper parts are margined with gray ; the postocular and rictal 

 stripes are less clearly defined than in adults; and the blue throat 

 is only partially developed. I have seen birds in this plumage in 

 July, August, and September. Probably the fully adult plumage is 

 not assumed until the following summer, for I have seen birds in 

 this plumage in March and April and as late as June 12. 



Food. — In Ramsay Canyon, this hummingbird feeds regularly and 

 fearlessly at the flowers in the gardens about the cottages and even 

 in the greenliouses, where it doubtless secures small insects as well 

 as the nectar from the flowers. Mrs. Bailey (1928) says that, in New 

 Mexico, its food consists of "insects from flowers of the shrubby honey- 

 suckle, gilia, agave, and other plants." 



In the summary of the contents of three stomachs, Cottam and 

 Knappen (1939) include fragments of true bugs (Hemiptera), small 

 beetles, flies, wasps, spiders, daddy-longlegs, pollen grains, and plant 

 fiber. In two stomachs 10 percent and 15 percent, respectively, of 

 the food was pollen. "One bird had made 92 percent of its meal on 

 seven specimens of a fly {Hypocera john^oni), which is rare in 

 collections." 



Behamor. — The flight of the blue-throated hummingbird seemed 

 to us to be exceedingly swift, as it whizzed by us up or down the 

 stream, uttering at intervals its squeaking note. It always seemed 

 to fly directly over or along the stream; and it was gone almost as 

 soon as it appeared. It was not at all shy and seemed to pay little 

 attention to human beings, coming into the gardens freely while 

 people were about. It would often alight within a few feet of a 

 quiet observer and seemed to spend much time perched quietly on 

 some dead twig, treetop, or other open perch. 



Voice. — The only note we heard was the squeaking note, which was 

 repeated every few minutes; Mr. Willard (1911) noted that the 

 second note is higher pitched than the first, and the third note lower 

 than either of the other two. Mr. Ray (see Rose Carolyn Ray, 

 1925) refers to it as "a rather far-reaching but not overloud alarm 

 note, 'seek'-*seek'-'seek'." Dr. Alexander Wetmore (1932) says: "The 

 birds utter sharp, squeaking calls, and the male has a simple song of 

 three or four notes, repeated at short intervals while the singer 

 perches upright with head elevated." 



Field marks. — This large hummer is not likely to be confused with 

 any other hummingbird except the almost equally large Rivoli's. 

 The most conspicuous field mark of the blue-throated is the long, 



