84 OUR NATIVE BIRDS 
have to take newly sawed lumber, rub the boards with 
moist earth. Limbs and trunks may, of course, be bored 
out, or they may be ripped first, then a cavity cut out, 
and the two halves screwed together again, but these 
boxes are likely to open along the joints unless very 
carefully made. Do not nail false bark on the boxes; 
it is never quite tight and only harbors bird parasites. 
It is, however, advisable to fasten the bark on summer 
cut wood with small nails. On wood that was cut in 
late autumn or in winter, the bark adheres naturally. 
The wood of rough-barked deciduous trees is best for 
bird boxes, but any kind of wood may be used. 
The width of the entrance hole, the location of the 
box, and its height from the ground must receive 
careful attention. Birds do not like to approach their 
nests over wide open spaces. The old nesting material 
should not be removed from the boxes, the birds will 
attend to that themselves. The boxes must not be 
exposed to the noon and afternoon sun, and small 
openings should be left between top and cover to 
secure ventilation. 
It is absolutely necessary to fasten the boxes well. 
If they are shaky and are rattled by the wind, or if 
branches and twigs strike against them, the birds will 
not use them. The fastening may be done by means 
of strong wires, nails, or screws, the method depending 
somewhat on the value of the tree to which the box 
is to be fastened. 
Some of the best European observers advocate sur- 
rounding the boxes of titmice and wrens with thorns. 
