Thursday, June 11, 2009

So Who Is Really Living Here?

It’s not that we don’t like House Wrens. We do appreciate the male’s beautiful warbling song that lets us know there’s pride in his chosen nest site. It’s just that he has chosen a nestbox that is supposed to be for the Eastern Bluebird. The bluebird builds a tidy nest, usually with pine needles because of their availability but we’ve seen dried grass used also. However, the House Wren stuffs the box with coarse sticks, cramming them in so tightly that it’s almost impossible to check for eggs. The actual nest cup is deep inside along the back side of the box so we dutifully (and carefully) tilt the nest outward and downward in order to see into it. If there are eggs or chicks, we leave them. However, if it’s the beginning of a nest we remove it but, usually, the next week the wren has been at it again.

Now we have discovered something new – new to us, that is. There are double layer nests in some of the boxes. The House Wren is either an opportunist or is lazy but, then, there may be a fine line of distinction there and could be a subject for musing in a different venue. On the bluebird trail here at the garden, we have several nestboxes in which the bluebirds started building nests but, somehow, the wrens took over. After all, they are feisty little birds. In one there was one bluebird egg already laid and we expected to find a few more eggs the following week. Instead, we found a stick nest built on top of the pine needle nest and the bluebird egg was gone.

We know that House Wrens usually choose boxes that are near woody areas and we thought we had placed them far enough from trees and bushy areas. However, now we know these birds will use boxes that are out in open areas and, in fact, will take over the boxes already being used by the bluebirds.

Wrens are known to destroy bluebird eggs by punching holes in them, but they also will attack chicks in the nest and toss them out. They are a major problem if one is trying to have a successful bluebird trail. Obviously we are distressed when we find these stick nests, but we also know that it’s nature at work. But double layers? Oh, come on!

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