As you start to build a bluebird nesting box trail, not all of the nests will have bluebirds. Here is some help.
- If you find little sticks in the nesting box, sometimes even over the existing nest, odds are you have a wren trying to nest in your bluebird box.
- If you find debris, instead of grass, including paper, and weeds along with the grass, more than likely you have a house sparrow living in your bluebird house.
- Mice have made a nest in your bluebird home if you find milkweed, seed and coneflower seed heads in your bluebird nesting box.
- If the eggs in the nest are blue, but larger, like a robin's eggs, you probably have a starling nesting in your box instead of a bluebird.
- Remember that starling and sparrows are invasive birds, and you can take out the nest if you'd like. Other birds, like chickadee and nuthatch are songbirds, and should be left alone to hatch and raise their brood.
- If once you have eggs, they disappear, and the nest seems undisturbed, the culprit may be a house sparrow, raccoon, snake or wren.
- If the bluebird eggs are found shattered on the ground or in the nest, it could have been a sparrow, red squirrel, chipmunk or even a wren.
- If you find tiny holes pecked in the eggs, a wren is usually the intruder.
- If you find your nest partially pulled out of the nest hole, and the eggs or chicks are gone, a raccoon or cat may have gotten to your bluebird house.
Here are more things you'll find with possible solutions:
- The nestlings are gone, but parents still around: could be cat, sparrow or snake.
- Nestlings dead outside box, sometimes 1 per day: sparrow
- Nestlings suddenly dead, stomachs full, bodies unmarked, parents still around: pesticide
- Young nestlings found dead in a wet nest: hypothermia
- Nestlings dead in nest, little blackflies all around, red welts under the birds’ wings: gnats or blackfly infestation.
- Nestlings dead in nest, large red welts on bodies, black pupae or gray maggots under nest: blowfly infestation
To prevent many of these, make sure your bluebird house is built correctly, or you buy one built correctly. It must have ventilation holes, drainage holes, it should have a predator guard, this could be incorporated in the hole or on the mounting pole, or both. The hole should be properly sized for the bluebirds in your area, and clean out the nest after each brood leaves. Check your nest boxes often.