166 THE ZOOLOGIST. 
at first proceed by the direct horizontal mode of flight. Begin- 
ning some time before and continuing for some time after 
passing the observer, they develop a regular series of the lower 
form of movement, and then resume their ordinary flight. The 
simpler evolutions may occur at any time under the pressure of 
an immediate cause, which I believe always to be some form of 
danger. With this exception, the evolutions, and more especially 
the complex forms, are confined to the period when the tide is 
above mean water-level, with a greatest probability of display at 
or about high-water. There are at least two possible reasons 
for this circumstance. During the period between half-tide and 
high-water the supply of food gradually diminishes, following 
several hours of plentiful and rapid feeding. This would mean 
that the restlessness prevalent after half-tide is an exhibition of 
superabundant energy without the usual outlet. That the 
evolutions are not due to mere restlessness may be inferred 
from the following consideration. In places where birds of prey 
are rare or absent, and in early winter before much shooting 
has taken place, the Waders may, and often do, come in with 
the flow to the high-water mark and go out with the ebb, without 
ever leaving the ground. Under what may be regarded as ideal 
conditions of feeding and security, they prefer to exert them- 
selves as little as possible. This observation should be kept in 
mind when one attributes to an overflow of energy the extensive 
displays which occur later in the winter without any cause 
obvious to casual inspection. The other reason is that the 
period of high-water is the time of greatest danger actual or 
potential. The rise of the tide crowds the Waders together, 
and makes them a conspicuous and an attractive mark. This is 
well known to man and predatory birds. In many places the 
Waders are known to leave the foreshore at some fairly definite 
time before high-water, and go to a distant place of refuge. If 
the Waders have been much disturbed, the first flock to arrive 
usually performs more or less extensive evolutions before it 
alights. Later arrivals generally fly in directly when they see 
birds of their own kind already settled. The report of a shot- 
gun, fired at as much as six hundred yards distant from Waders 
on a refuge, makes them rise and perform their evolutions. At 
each repetition, as the birds find out that no harm results, the 
