BIRDS IN RELATION TO AGRICULTURE 181 
construction and size is a matter upon which taste can be 
exercised if the following directions are followed: 
If possible they should contain not less than ten to twelve 
rooms. ‘The individual chambers should measure six inches 
square and high, and they should be completely separated 
from the adjoining chambers. The entrance holes should 
measure two and one-half inches in diameter, and the 
centre of the hole should be slightly above the centre of the 
outer side of the chamber. 
2. THE DESTRUCTION OF ENEMIES 
The greatest enemy to bird life in more thickly populated 
districts is the domestic cat. After many years’ experience 
I have arrived at the conclusion which all lovers of bird life 
reach, namely, that no matter how carefully a cat is cared 
for by its owners, its bird hunting and destroying instinct 
is not greatly diminished. Naturally, stray cats will destroy 
a large number of birds, and such garden-loving species as 
robins and yellow warblers fall an easy prey. The destruc- 
tive character of the cat has been well described by E. H. 
Forbush in his book, “‘ Useful Birds and Their Protection,”’ 
and in other publications. The following evidence is given 
in his book: 
Mr. William Brewster tells of an acquaintance in Maine who said that 
his cat killed about fifty birds a year. Mr. A. C. Dike wrote of a cat 
owned by a family and well cared for. They watched it through one 
season and found that it killed fifty-eight birds, including the young in 
five nests. 
Nearly a hundred correspondents scattered through all the counties of 
the state (Massachusetts) report that the cat is one of the greatest enemies 
of birds. The reports that have come in of the torturing and killing of 
birds by cats are absolutely sickening. The number of birds killed by 
them in this state is appalling. 
Some cat lovers believe that each cat kills on the average not more 
than ten birds a year; but I have learned of two instances where more 
than that number were killed in a single day, and another where seven 
