Click photos to enlarge.
date. The other three hatched the following day. My daughter and her family from Texas were here and got to see them as well as my son and his wife. Neighbors came over to look, too. It’s amazing that the bluebirds are so receptive to my showing off their babies.
Mama II and Daddy II just sit on their perch and watch, but don’t fuss or seem nervous. My original Daddy would dive bomb strangers. This pair is really not aggressive enough. They don’t do a good job of running away sparrows like my first pair. The original Daddy would chase sparrows with such zeal, most would just leave the area because they knew they were going to be under constant attack. Maybe as these birds mature they will be more protective of their nest.
When I found the first chick had hatched, the few feathers it has were not yet dry. Mama had eaten the eggshell, as females do, to replenish the calcium in their bodies. One more egg hatched the next morning and the final two later in the afternoon.
Hatching babies use an “egg tooth”, not a real tooth but a small sharp temporary
structure on the top of their bills, to cut through their shells from the inside. You can see the “egg tooth” in the photo.
Using a special muscle in the back of its neck an embryo rubs its egg tooth against the shell, which has already been thinned and weakened as the growing embryo absorbed calcium from it for its bones.
When the shell is finally cut, the hatchling works itself free of shell membranes and separates itself completely from the shell halves.
Today the work really begins for the adult bluebirds. For seventeen days it will be bugs in– poop out from daylight til dark.
See more bluebird photos on my flickr stream at http://www.flickr.com/photos/reddirtpics/sets/72157627747745082/
Total bluebirds fledged from this nest site since 2009 is 45.
Fourth Brood Summary
- First sign of nest building 12 July
- Nest completed 15 July
- First egg 16 July
- Second egg 17 July
- Third egg 18 July
- Fourth egg 19 July
- Incubation begins 20 Jul
- 1st baby hatches 02 Aug
- 3 babies hatch 03 Aug