The Black-chinned Hummer 
arrest (at near range), it becomes of interest to note the wings of this 
tiny aircraft, and the pectoral muscles,—the engines which drive them. 
Compared with other birds’ wings, those of the hummingbird are seen to 
be very much shortened 
basally—shorter lever¬ 
age and added power. 
The breastbone, or ster¬ 
num, serving for the at¬ 
tachment of the muscles 
which actuate the wings, 
is extraordinarily devel¬ 
oped. It extends back¬ 
ward beyond the 
attachment of the legs, 
beyond the sacrum even, 
save as that is prolonged 
by processes which sup¬ 
port the no less fully 
developed tail. The 
breastbone, moreover, 
is of an extraordinary 
depth, so that the skeletal hummer is like the body of a racing yacht, 
all keel. With such an equipment, a hummingbird can reel off a course 
a thousand times the length of its own body in a single second, and per¬ 
form evolutions whose rapidity has no other near competitor in the realm 
of living nature. Or, let us say, to cap this climax, that the tip of a 
hummingbird’s wing travels further through absolute space than any 
other wing in the world. 
The Black-chinned Hummer indulges the tower-and-dive tactics in 
courtship, as do other hummers, but its performance is, perhaps, less 
spectacular. The loop of downward flight is less acute, and its altitudes 
are not so dizzy. The climax is marked by a low, musical, murmuring 
sound of considerable beauty, and there are spirited chipperings, besides, 
of so dainty a quality as to baffle the most careful student of distinctions. 
The Black-chin has, however, one fashion all his own, which makes 
him a prince among these fairy lovers. At what might be termed the 
sofa-and-low-gas stage of courtship, the male disports himself before 
his lady-love in a passionate effort which I call the rocking song. She 
is seated in the center of some bower, perhaps the tempered shade of 
a live oak tree. The lover sways violently before her through the arc 
of a small circle, like some feverish pendulum-bob; and as he sways he 
gives vent to his emotions in a dropping sound of passionate intensity. 
957 
