What about ants?

Ants can be a really big deal to birds. They can kill both eggs and any young in the nest, so it is important to get to them quick.

Many pesticides have chemicals that are severely harmful to birds.  The chemicals can also leach into the wood and stay there for years. So you should be exceedingly careful with any pesticide you choose. However, one available option is borax. It is a odor-free, non-toxic chemical that you can mix with water to make a good pesticide. You can spray borax around the base of the nest box pole, spray it on the pole, and also soak q-tips in it and duct tape them to the bottom of the box. Borax is usually available at any drug or hardware store.

Another option for the wasps is also using soap on the roofing instead of vaseline. Soap provides a waxing coating that does not get as sticky as vaseline. Using a scent-free soap will also not be a detriment to the birds. However, you may have to apply several coats for it to be effective.
(Answer provided by Kenyon Stratton, NestWatch Project Assistant)

Clean or leave nestbox alone?

I have a nest box that Eastern Bluebirds have nested in previously. A pair has been hanging around the box again this year. Should I clean out the old nest that's still in it or leave it alone?
Look in the box. If it looks like the old nest from last year, remove it. If only one nest from last year is in the box and the pair have started nesting, leave it be. It would not be unusual for the bluebirds to start nesting in mid February in Alabama. If it is the old nest, the nesting material (if grass) will be a slight brownish color much like silver tarnish. The grass may also be matted down if babies fledged last summer with bird fecal matter strewn about. If this is the appearance of the contents of the box, then go ahead and remove the old nest.
The most prevalent school of thought is that nests should be cleaned out each time the young fledge. One advantage is that removing the old nest keeps the next nest that is built at a safe (from predators) distance from the entry hole. 

Do Eastern Bluebirds Migrate?

Do Eastern Bluebirds Migrate in Alabama? I seem to see more during the winter months.
Resident Bluebirds migrate short distances looking for a better source of food but generally stay pretty close to where they were raised. Bluebirds are insect feeders so we do have an increased population during winter when northern birds come south looking for food.

At What Temperature Can Bluebirds Eggs Survive in a Nestbox?

We asked Cornell Lab of Ornithology and this is their reply: The optimal range for egg incubation is 96.8° F to 104.9° F  [36° C to 45.5° C] Once those box temperatures increase into the 90s the heat itself will start incubation. Higher than 104.9° F and the eggs or nestlings are unlikely to survive.