Just because eggs are blue doesn't mean they were laid by a bluebird. Bluebirds are cavity nesters, and VERY rarely lay their eggs outside of a cavity. (When desperate, they may use a ledge.)
Some people who report finding bluebird eggs in odd locations (in a potted plant for example) are really seeing eggs of another species, like the American Robin. House Finches are the only small cavity nester I can think of that lays eggs that are bluish-green. About 4-5% of bluebirds actually lay white eggs.
Robin hatchlings are much larger than bluebird hatchlings, and have longer tufts of white fuzz along their spines and forehead.
Bluebirds have taught me a few things. First, the more you think you know, the more you have to learn. Second, never say never because they will fool you every time! Third, they have taught me to stop sweating details in my life and learn to enjoy the simple things. There are things far greater than ourselves out there, going on unnoticed right before our eyes.
- Malinda Matsuko, Bluebirder, 2005
