Second Wren Brood

After the wrens fledged at the end of May, I left the empty nest on the shelf in the garage, thinking they might use it again.

I had been checking the nest intermittently and on June 23rd, there were two eggs in it. When I told Mary about it, she said she had seen a Carolina Wren fly out of the garage the day before and had looked in the nest and hadn't seen any eggs.

I then checked the nest every day after: June 24th, 25th, and the 26th, and every day there was another egg in the nest. The mother wren stopped laying at 5 eggs, so this brood is 1 smaller than the last one.

I've read more about Carolina Wren nesting habits. There are several resources on the web. This is a good one. There is another good one here. The wrens mate for life and typically have two broods a year. The male usually makes several nests and the female picks which one to use. The multiple nests may be to confuse predators as to where the eggs are.

We attended a talk by Dr. Peter English, who is from the School of Biological Sciences at the University of Texas in Austin, about birds at our last Hays County Master Naturalist Chapter meeting. He mentioned that bird eggs average about 20% of the mother's body mass in size and how incredible it is that she lays one a day for several days. I think when I saw the two eggs on June 23rd that she started laying the second brood on June 22nd and we just didn't notice them until there were two eggs in the nest.

This means they should hatch about 12 to 14 days after, around July 4th to 6th. One thing I'm not sure about is how they can hatch synchronously, within a day of each other, if they were laid a day apart. A day difference in a total of 12 to 14 days of development seems fairly significant. I'll keep an eye on the nest and see when they hatch.