Last year I remember reading about how vicious wrens can be, but until today, I hadn't really witnessed it.

First off, I like wrens. These are the common everyday house wren I'm speaking of. They have such a melodic call.

They nest in either or sometimes both of my 2 nest boxes each year, although in recent years, I've had bluebirds who occasionally get to nest in one of them, like last year. I would say 80% of the time its wrens that end up with the boxes and 20% of the time its bluebirds. (Once I had an English sparrow but I took the box down rather than have them nest there.)

I have a decent view of the box in the backyard from my sunroom. I was just out there when I noticed a wren popped inside and kept sticking its head up and out the hole, with a small piece of straw in its bill, which it unceremoniously dumped each time. It was clearly trying to clear out another bird's nest, something that didn't surprise me as I had seen a male bluebird hanging out around that box just yesterday.

However, I know that many male birds begin building more than one nest to entice the female; the female will ultimately choose which one she wants. I figured the bluebirds could still take the box in in the front yard.

Then I saw the wren fly down to the ground below the box and raise its head up and down rapidly in a staccato movement. I saw a flash of blue. I jumped to my feet and ran out to scare it off. But it was too late. The wren had pierced a bluebird egg with its bill. I saw the shell of what must have been a second egg on the ground.

The male bluebird was by minutes later; it must have seen the broken shells on the ground because I heard a distressing, chattering call as it flew away.

I chased the wren away twice more when it returned to the box, but obviously I can't keep that up and if the wren wants to nest there, I guess it will.

Very sad. I have no shortage of wrens around here, but it is a pure pleasure and a privilege to see flashes of brilliant, indigo blue around my yard all summer when the bluebirds are nesting.

As for the front box, I had noticed bluebirds in that area quite early on but I wanted to insert some fine mesh wire on the bottom of the box to prevent a certain kind of flying insect from laying its larvae there. The larvae crawl up and attach themselves to the baby bluebirds' legs and are parasitic, sometimes causing the death of the baby bluebird. The wire mesh prevents the larvae from crawling upward to the nest. When i went to insert the wire mesh, I was surprised to see an already half-built bluebird nest, and I'm afraid I partially destroyed it when I inserted the wire mesh. I haven't seen bluebirds there since. So inadvertently, I may have scared off the bluebirds from that box.

I was thinking of moving the nest in back so its further away from the scrubby, brushy areas that wrens favor, and more in an open area, which bluebirds favor. But there aren't many open areas of my yard where i don't have to mow weekly, so that would represent a disturbance to the bluebirds. And, I'm not sure if there are any more eggs in that box. If so, I don't want to move the box as the bluebirds might not return to it, but as it is, the wren will likely dispatch of it anyway.