Mrs. Bluebird has definitely started incubating her four eggs. Thursday, she sat on them most of the morning before spending most of the afternoon out of the box. She stayed in the box Thursday night, sat on the eggs Friday and again spent the night. The book says it takes 11 to 19 days for the eggs to hatch. Let’s say she started Thursday, that means they should hatch sometime between May 2 and May 10. Here’s a good look at her sitting on her  eggs.  About 11:00, you can see her turn the eggs. All birds turn their eggs while incubating them. Theories as to why include, rotating the egg helps deliver albumen – the ‘white’ of the egg that is protein – to the chick – the ‘yolk’ and that turning the egg helps warm the egg evenly and and prevents the egg’s membrane from sticking to the shell. 

We’re looking inside a nesting box with the bluebirds in West Newbury, Vermont. The camera is permanently mounted in the box and we can watch without disturbing the birds.