Thursday, July 03, 2008
We get lots of questions about nesting birds, especially nesting bluebirds. People cherish their bluebirds and worry about the things they see their bluebirds do. For example, here's part of a recent question to us about bluebirds — "There have been 3 eggs in the box now for going on 2 weeks. I’m guess the eggs are not viable but momma is still in the box laying on them???? What to do?? Do I remove the eggs? Remove the whole nest? Just leave things alone? I think they’ve been there too long now to hatch – yes/no/maybe so?? Please advise."
Here's some basic information about bluebirds to calm worries.
- Eastern Bluebird females build the nest out of fine grasses or pine needles and it can take as little as 2 days, but 4-5 days is the average.
- Once the nest is built, egg-laying can begin in a day or two' but may not begin until a week later or so. So don't panic if you see a built nest and no eggs right away, it does not mean the bluebirds have abandoned it.
- Females lay one egg per day in the morning and spend very little time at the box during egg-laying. The eggs can remain there at air temperature with no harm to them. So just because you see a nest and several eggs and no female, does not mean the nest and eggs are abandoned. She can lay 1-6 eggs in a clutch. If one or some of the eggs are infertile, but not the others, she may leave the infertile egg unhatched in the nest, or the parents may try and remove it. Bluebird eggs are blue but in 9% of the cases they have been found to be white.
- Only after the last egg is laid does the female do full-time incubation. She takes breaks every once in a while to go feed, preen, take a bath, take a break, etc. In warmer weather, she may leave the nest for longer periods of time. Incubation can last 12-18 days.
- After the eggs hatch both parents feed the young and remove the fecal sacs (little white diaper like sacs) from the nest. The parents feed each young about two times an hour, regardless of how big the brood.
- The length of time the young are in the nest for the Eastern Bluebird varies from 16-21 days. It is OK to look into the box once or twice a week to check on the progress of the bluebirds. Your scent on the box will not cause the birds to leave (most bird species have very little sense of smell). Do not look in the box once the young are 12 days or older as this may cause them to premature leave the box before they are ready.
For more complete information see Stokes Bluebird Book.