Date: 6/19/19 9:31 pm From: Maeve and Dick <maeveanddick...> Subject: [obol] House Wren are vicious predators
We have 41 nesting boxes on our 10 acres about 5 miles south of Eugene. I have been managing bird houses for close to 40 years, 24 years at our current location. Our target species is Western Blue Birds but we do not have the best habitat for them so we get lots of Violet-green Swallows, Tree Swallows, Black-capped Chickadees, Chestnut-backed Chickadees and of course House Wrens. House Wrens do not play well with others! Every year we have nests that have been destroyed by House Wrens. They break eggs, kill chicks, sometimes kill adults, throw eggs and chicks out of the nest and rip the nest apart and throw the materials out the hole! They also fill houses with sticks so other birds cannot use them. We have been having about 20 to 25% of our nests destroyed or houses filled with sticks by House Wrens over the past 15 to 20 years.
We checked our houses today and we have had nine houses where the eggs and chicks were killed by House Wrens and another nine filled with sticks. That is a total of 44%, much higher than any previous year!! This is discouraging to us and upsets us to see so many eggs and chicks killed. If anyone has a thought as to why the seemingly sudden increase in the number of House Wrens, let me know. We are researching for bird house modifications that seem to discourage House Wrens but still allows other small birds to use the box.