How do you make sure the "right" animal is using your bird houses and bird feeders?

Learn all you can about the birds you want to attract and offer them a
box that opens at the top and the front or side. Monitor the nest box,
and evict starlings and house sparrows.

The safest solution to insect infestations is physical removal and
soaping the inside top of the box. If insects infest the box during
nesting, apply a light dusting of rotenone or pyrethrin. Do not use
chemical sprays.

If snakes and climbing mammals are a problem, use physical barriers to
deter them. Try a PVC pipe over your metal bird house pole, or metal
sheeting on a tree or wood pole. Smear the PVC or metal with Vaseline
laced with hot (cayenne) pepper. Avoid automotive grease, it can be
lethal to wildlife.

Put a predator guard over the nest entrance hole.

Do not use bird houses with perches below the entrance hole.

If you find birds attacking the adults, eggs or nestlings, what you can
do depends on the perpetrators. Eliminate house sparrows and starlings.
All other birds are protected by federal and state laws. You may not
harass or otherwise harm hawks, owls, falcons, crows, grackles, jays and
shrikes.