140 THe Orrawa NATURALIST. [October | 
In one instance, when the birds located in a dead maple 
trunk set up for them within a few feet of our own house, the 
birds worked alternately at mining or excavating the hole in 
which the nest proper was placed. The length of time one would 
work varied from a few minutes to thirty. Then it would call a~ 
few times, and the mate wouid appear upon the scene and take a 
shift at the work. Toward the last of the mining operations the 
male performed that work and the female was busily engaged in 
collecting material for the nest. This consisted of fine shreds of 
cedar bark, other fibrous material, hair and a few small feathers, — 
and the whole was well fitted together. 
The excavation had been enlarged to satisfactory dimensions, 
which were as follows : entrance oval, one inch by one and one- 
eighth in diameter, leading inward an inch and one quarter on 
lower side, then downward six inches and enlarged to nearly 
four inches across for half the lower tunnel. 
The next cavity measured about one and one-half inch in 
diameter and depth. All chinks and cracks within the excavation, 
if they lead to the outside, are tightly caulked with fibrous mate-_ 
rial of the same composition as the nest. 
Before the female had completed the nest, the male began 
carrying fir balsam, from the trees surrounding their home, and 
besmeared an area about the entrance to the nest, fully four inches 
in diameter. 
The Nuthatches we may consider our only birds which use 
artificial weapons for their protection. The entrance to the nests 
being always fortified by means of balsam, which seems to be 
applied for the purpose of keeping out the white-footed mouse, an 
omnivorous little rodent that would gladly avail himself of the 
opportunity of making a meal of the eggs or young birds, or drive 
away the old birds and use the nest for its own tenement. 
The egg of this species of Nuthatch are usually six in num- 
ber, white, with brownish spots, chiefly near the large end. Some 
sets contain eggs nearly spherical in form. ‘ 
The duty of incubation is performed by the female and covers 
a period of twelve days. The male occasionally feeds his mate 
during this period, adds more balsam about the entrance to the 
nest, and does general pickei duty about home. When hatched, the 
