Incubating time on the Blue Bird Trail

Post contributed by Sharon, volunteer Blue Bird Trail monitor:



Feather-lined tree swallow nest with 4 eggs

Two boxes are empty now after I removed small amounts of moss and grass that had been sitting untouched for two weeks. The house sparrow pair gave up and moved elsewhere after I cleared their nest last week, and that box is now occupied by bluebirds.

I could count six chickadee eggs and two cowbird eggs in the chickadee nest. Last week, I saw seven chickadee eggs. It is very possible that seventh egg is hiding out of view of my camera. I use a small camera to see into each nest in the Peterson-style boxes on the trail, because the boxes are mounted above my eye level.

The cowbird eggs may hatch as early as tomorrow. Depending on when the chickadee began incubating her eggs, it could be as late as next Wednesday before the chickadee eggs begin to hatch. That would be bad news for the young chickadees, as they would be so much smaller than the cowbirds and could easily be trampled or smothered. If the parent birds are busy feeding cowbirds before their own eggs hatch, I wonder if incubation would even be able to proceed successfully?

Tree swallows have laid seven white eggs in two boxes.

The number of bluebird-occupied nest boxes held steady this week at six, even though that new nest was made in the former house sparrow box—one nest I had identified last week as a sparsely-made bluebird nest actually belonged to tree swallows! There are now a total of 19 bluebird eggs in these boxes.