COSTA'S HUMMINGBIRD 363 



young she would probably have been detained beyond the usual time 

 for migrating." 



Courtship). — The courtship performance of Costa's hummingbird 

 follows the same general pattern of that of other hummingbirds, con- 

 sisting of spectacular swoops, dives, and loops in the vicinity of its 

 observing mate. James B. Dixon (1912) says that for a short time 

 prior to the nesting season "they are quite noisy, chasing each other 

 up, down and around through the surrounding bushes and trees." 

 He continues: 



Their note consists of a few sharp squeaks, given out more often when in very 

 rapid flight than otherwise. During the breeding season the male has a 

 very peculiar way of disporting himself before the female. "When he locates 

 his mate sitting on a tree, or more often on a low bush, he will ascend to an 

 elevation of about one hundred feet and to one side of the female and will then 

 turn and swoop down at a fearful speed, passing perhaps within a few inches of 

 the watching female and ascending in the air to complete a half circle. This 

 he keeps up until the female becomes impatient and endeavors to escape; then 

 perhaps all that one will see is a streak, and a shai'p squeak or two is heard 

 as they flash up the hillside. The noise that the male makes in doing his 

 fancy dive is easily heard at some distance and quite often heard when the 

 bird himself is not visible on account of the extreme speed at which he travels 

 on his downward plunge. 



Mr. Woods (1927b), in comparing the performance of this hummer 

 with that of the Anna's hummingbird, says : "The Costa's Humming- 

 bird, instead of making a more or less abrupt turn, sweeps through 

 a great arc to describe an immense letter U, then passes overhead to 

 shoot downward again, either from the same direction or at a new 

 angle. A continuous shrill whistle or miniature shriek accompanies 

 most of the downward course and part of the upward — in other 

 words, that part of the circuit in which the velocity is highest. This 

 Hummingbird often ends his series of loops by darting away at high 

 speed in an erratic, zigzagging flight." 



W. L. Dawson (1923) says that the sound made by the male hummer 

 in this flight is, he believes, "the very shrillest in the bird world, 

 and one which is fairly terrifying in its intensity. This sound is 

 generically like that produced by the Anna Hummer, but it is much 

 more prolonged and more dramatic, more, in fact, like the shriek of 

 a glancing bullet, or a bit of shrapnel." 



Nesting. — Dr. T. S. Palmer (1918) has published an interesting 

 paper on the early history of Costa's hummingbird, in which he makes 

 the rather surprising statement, with the supporting facts, that "the 

 first specimen, the first eggs, and the earliest nest of the season were 

 all found in the southern part of Lower California at localities only 

 a few miles apart. Twenty years elapsed after the species was first 

 discovered before it was actually collected in California and nearly 

 fifty years intervened before the eggs were found in the state." 



