I have not seen my bluebirds in a couple of days.
I read bluebird facts on the North American Bluebird Society web site and learned I should have been checking on the bluebirds nest every week. Today I opened the nesting box and saw 2 eggs, hopefully the mother will return to incubate the eggs. The mother can lay 4 or 5 eggs and it's possible these eggs didn't hatch. I didn't see any hatched eggs inside or outside the nest so maybe the mother went for food and will retunn to incubate the eggs.