Wren fatalities

[Luger]

CObirders, I'm puzzled. Last month we hung a Wren box and got a tenant almost immediately. This week for two days I watched a wren bugging and carrying insects back to the box. Then yesterday I found a wriggling hatchling in death throws on the ground beneath the box and another hatchling dead a little further away on the ground covered with ants. The dead bird, though further from the box, still had the shell with the body. Just above my head there was a wren watching me from the house opening. The one still alive had a tiny bloody hole on the back of its head that looked like a beak pinch mark from where it was tossed from the box.

What the heck happened? Did the parent kill the hatchlings? Has anyone seen this happen before? There is still a Wren coming and going but not with food.

Perplexed,

Myrna Luger
Across from Horsetooth Mtn Pk

[Alison Kondler]

I'm guessing, competing House Wrens. House Wrens will pierce eggs and evict tiny babies of ALL species nests near their nest. I guess for less food completion. If they see a nest box hole occupied by other wrens from their nest box vantage point, one will win out. Place boxes away from the sight of one another and you might not have as much fatality.

Alison Kondler
Jefferson County

[markc...@comcast.net]

We had a situation happen this spring with this kind of behavior.  We were thrilled to have Red-breasted Nuthatches nesting in one of our boxes here in Lakewood.  I watched the activity as the birds went in and out of the box for nearly two weeks.  One morning, I heard the male calling over and over outside of the box.  The next day I noticed the wrens were inspecting the nest.  I grabbed a ladder and looked inside to find three pierced nestlings.  The nuthatches moved on and the wrens took over the box.  We also had Flickers nesting in a box to find their nestlings thrown about the yard and Starlings in the box.  We sealed up the hole with popsicle sticks to keep the Starlings out.  After much persistence the Starlings gave up but the Flickers never returned.  Nature is cruel!!

Mark Chavez
Lakewood-Green Mtn
http://jaeger29.smugmug.com/

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[Kay Niyo]

I learned the hard way in IA with my bluebird trails that both House Sparrows and House Wrens are notorious for killing Eastern Bluebirds and other birds in nest boxes.  If you run a bluebird box trail in a state east of CO (perhaps in eastern CO also), you have to pull out House Sparrow (not protected) nests weekly and House Wren sticks (pulling out sticks only that the male puts into several houses prior to nest building is legal).  Never put up a bluebird box anywhere near trees or the House Wrens will move in; keep the boxes in the grasslands.  The wrens drive the bluebirds out of the box and build sticks and a nest on top of the now cold eggs.  And they also will pitch out bluebird eggs, nestlings, and kill nestlings in the boxes.  Then they stuff the house with sticks right over the bluebird nest and the female wren builds a grass nest in the sticks.  As shown in this thread, wrens do the same thing to other species unfortunately.

 

We had many bluebird predators in IA!  When I moved to CO, I was amazed that our bluebird trail in Elk Meadow in Evergreen rarely had trouble with any predators.  A very pleasant trail to care for!

 

I tried putting up lots of boxes on my pine mt property above Evergreen to try to keep the wren pair happy and accommodate the Mountain Chickadees and Pygmy Nuthatches.  That worked.  So, maybe more boxes might be a solution.

 

Kay

 

Kayleen A. Niyo, Ph.D.

Niyo Scientific Communications

5651 Garnet St.

Golden, CO 80403

303.679.6646

K...@KayNiyo.com; www.KayNiyo.com

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[Comcast]

I would never have thought such a tiny and cute bird could be such a ruthless predator. Just a Wren eat Wren world out there I suppose.