Ah ha! So that’s Why My Female Bluebird is not Incubating…

eggs5-1000950So our bluebird family now has 5 eggs in the box and very rarely in the past 5 days have we observed the female actually IN the box. In fact for the most part, there’s been no sign of her. (For those of you who may not have been following along, we have a bluebird box in our yard with a camera inside it that transmits the video onto our TV) I have wondered about this, especially since it has been fairly cool for the past few nights. Why isn’t she sitting on the eggs, I wondered. How can they survive uncovered in the cold nest?

Well this afternoon I was visiting with my friends Laura and Hal Mahan, owners of a wonderful store in Biltmore Village called The Compleat Naturalist and was discussing it with them. What I learned is that most birds don’t start incubating the eggs until ALL of the eggs have been laid. This way, the eggs will hatch at the same time and one baby won’t be 5 days older than the other babies. If one baby is older and then bigger, it may take all the food from its siblings or may even kill its siblings. To avoid this, the female waits until she is done laying all the eggs. This is called synchrony.

The crow is an exception to this rule, as the female begins incubating as soon as she lays the first egg. Why does this work for crows? What makes these chicks not kill their siblings? What other species of birds practice asynchronous incubation? I don’t know the answers! But in the coming days, I will try to learn it and publish a future post about it. So, as always, stay tuned!

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