218 THE COMMON BIRDS 
tice a nest may often be recognized at once 
from below, but even the most experienced may 
be sometimes wrong. The locality, position 
(tree, bush, bank, etc.), and average height of 
the nest, the shape, size, markings and 
number (when the full clutch is laid) of the 
eges (and these are all fairly constant) as 
well as the birds seen to belong to the nest (if 
possible), must be taken into account before 
a decision is arrived at. 
Eggs of all birds vary somewhat (study 
museum specimens for this) in size, shades of 
colour, distribution of the spots (and even 
their contour). But those wzthout spots do 
not vary much in shade. The number of the 
full clutch is almost always constant. That of 
second and third nests may vary. Eggs are diffi- 
cult to name, even from the best coloured 
drawings, or photographs, though photographs 
show well the general appearances of nests. 
Read up all the points of the birds and familiar- 
ize yourself with the photographs of them, 
especially good ones of diving specimens, or 
veliable coloured drawings. Visit museums, 
