434 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
other insects. Too often is this the case when trying to follow the 
flight of some small bird, the beating of the little wings being quite 
too rapid for our senses. We will here confine ourselves to those 
birds possessed of ample expanse of wing, for, generally speaking, 
the larger the wing the less rapid is the been! and therefore the 
more easily can we follow its movements. 
To gain the velocity in order to create the resistance necessary for 
the support of all heavier-than-air “machines,” some birds run or 
swim, others simply spring into the air and by the vigor of their 
flapping achieve the same result; while others, again, ence them- 
selves from some coign of vantage—a tree or rock—and in falling 
gain the desired resistance. In this article I give some aiporia 
regarding the latter method, illustrated by photographs of the 
Gannet (Sula bassana). 
Stepping to the cliff edge, ane if there is no cause for undue haste, 
having raised and partly unfolded its wings, the bird prepares to 
dive into space. This dive, it should be noted, is not directed down- 
ward, but rather as horizontally outward from the cliff as may be 
(sometimes it appears to have even an upward tendency). If the 
bird is one possessed of broad large wings not much altitude is lost, 
and it skims through the air in much the same fashion as does a 
piece of cardboard thrown horizontally. If, however, as im the case 
of auks, the wings are small and narrow and the body heavy, then 
the bird at first drops nearly vertically, only being able to gain a 
more horizontal course as its velocity increases. 
Sometimes birds of this latter class, presumably through mis- 
judgment of the space they have to work in, do not get the horizontal 
course in time, and crash into the rocks or sea at the foot of the 
cliff. This is very noticeable when a group of puffins (fratercula 
arctica) hurriedly takes flight from a steep bowlder-strewn slope. 
Under these circumstances I have frequently seen quite a number 
of birds come to grief on the rocks within 30 yards of starting. 
Most of these, though somewhat dazed by the impact, flutter and 
claw their way on to the top of some big bowlder, and after a 
moment’s pause again dive forth, but not infrequently with no- 
better result. The first failure is, I believe, often caused by their 
paying too much attention to and looking behind at whatever startled 
them, instead of gauging their proper angle. 
The raismg and unfolding of the wings is worthy of a little con- 
sideration. ‘The former usually takes place not after, but previous 
to, the diving or springing forward, while generally the whole “foot” 
is at rest upon the rock. Of course, when suddenly alarmed birds 
sometimes cast themselves from the cliff without first raising their 
wings, and in consequence fall rapidly. 
