Yes, then clean the box.
The eggs can fall from the nest, the eggs can be eaten or crushed by something, but the means really depend on the circumstances.
Yes, both bluebirds and sparrows are cavity nesters. This means they both use birdhouses to make nests in. Sparrows are very fierce and often when fighting with bluebirds they kill its babies or break their eggs.
Usually right around 2 weeks.
Watch the bluebirds closely to make sure that they incubate them. Also watch out for sparrows and other birds that may crack bluebird eggs or take over the nest.
They la 4-6 eggs per nest.
Sakura
you decide
theres no bird on them
remove the anthers
The eggs are not any good if found underwater.
a dove is the bird that lays pale blue eggs.
If the eggs have been left untended for more than 24 hours they most likely are or will die.