NOTES ON THE OYSTERCATCHER. 205 
tents. Occasionally empty shells are found which exhibit the 
depression of a fragment at the margin of one valve. 
The simplest procedure is to shake or lever the bill violently 
from side to side, and is sometimes successful in separating the 
valves, as the Mussels are fixed securely to the ground. The 
two methods most in use may be employed independently one 
after another, or may follow the method just described, as cir- 
cumstances require. 
One method is as follows: The bill, sunk vertically between 
and in line with the valves, forms a pivot of a movement of the 
Oystercatcher to one side of the Mussel. As the Oystercatcher 
walks slowly round the bill turns through quarter of a circle and 
comes to lie with its greatest depth across the fissure, causing a 
marked separation of the valves. The same effect may be pro- 
duced without moving the feet, by rotating the head to one side 
on a vertical axis. The other method is equally simple: The 
Oystercatcher lowers its head almost to the ground on one side 
of the Mussel, and the point of the bill, being well inside the 
shell, presses on the opposite valve which is separated widely 
from its fellow. This may have to be repeated several times. 
It is curious that, as far as observation goes, the Oystercatcher 
walks round or lowers its head to its own left side, and the left 
valve suffers more often than the right, because the bird ap- 
proaches the Mussel more often from the front than from 
behind. 
Now and again another and less simple method of opening the 
shellsis seen. It may be employed from the first, or after other 
ways have been tried and have been found wanting. I have 
seen a group of Oystercatchers use it to the virtual exclusion of 
other methods for several days, and then apparently it was 
abandoned for months. This method requires that the bivalve 
be approached from behind. The bill is pushed downwards be- 
tween the valves and behind the ligament, and perhaps, after 
ineffectual attempts to open the shell by lateral and rotary 
levering, the bill is drawn slowly and firmly backwards and 
downwards between the valves, until the head almost touches 
the ground behind the Mussel, and the bill, instead of being at 
right angles to the long axis of the Mussel, lies parallel to it 
between the margins of the valves at the posterior end. From 
