Bird Houses
If you want a bird house I can cobble one together from some scrap or salvaged wood and hopefully gourds. At least the birds are not particular about precision considering the alternative if available is a knot hole in a tree. Beside I have seen nice fancy ones fall apart upon exposure to the elements better yet to see a wide range check with the county extension office to find out when the 4-H bird house judging is held. The size depends on what species you want to attract. A purchased bird house can be installed as well.
Bat Houses
Bat houses are a little more involved due to the internal partitions. Most bats around here seem to prefer structures such as concrete block building rather than boxes although newer designs have not been tested. If they do this would be the most effective adult mosquito control.
Butterfly Houses
These would currently be purchased items. I'm not even sure if they are effective. A better idea would be a place more attractive to ladybugs than people houses so they stay outside rather than get inside each fall and yes they do exist, but it is just a question of whether they would work to keep the beneficial bugs outside.
Toad Houses
These are little more than places such as a nook where a toad can hide. They are included with general wild life enhancement such as logs and rocks or can be purchase through specialty shops. I have seen both common and narrow mouthed toads using mole tunnels.
