I don't like working with PT lumber, although I recently constructed a
park bench using it. You should work with it outdoors and with a
properly fitted dust mask. The splinters from PT wood are nasty and
take a long time to heal. For bird houses, I prefer pine. One pine
house is over 18 years old and still in use today--I think the tar
shingle on the roof helped preserve it. I also built a bat house,
made from pine.