Expert: Bluebird Bob Walshaw - 7/2/2009

Question
We recently put up two bluebird houses.  Tree swallows moved into one of them and they are really cool birds.  We set up binoculars in our bedroom so we could watch them.  They had four eggs; all hatched successfully.  One began sitting in the opening to the nest -- we could see his orange beak clearly as he begged for food.  The parents came and went feeding the babies.  Today we looked in the nest, having noticed no activity for a while.  Three of the babies were in there dead.  They were perfectly formed and feathered and had no marks on them.  Do you think they didn't get fed because the fourth baby was always in the entrance?  Or is there some other hazard to box nests that we don't know about.  We are heartbroken.  Thanks,
Esther.

Answer
There are several possibilities, although nothing is certain in the bird world. !. Were all the eggs exactly the same? If one was a parasitic Brownheaded Cowbird egg their babies will block the others and get all the food. 2. Tree Swallow babies need a scored surface or wire surface to climb out of a box. They are not able to fly to the opening as baby Bluebirds do. 3. And more commonly, if predators got the parents the babies starve. My free 20 page book does not cover tree swallows as I don't have them here, but you probably have Bluebirds there too. Send your mailing address to me at walshaw1@cox.net and I will send you the book. See page 19 about having more than one box and the house sparrow trap contacts. Bluebird Bob.