"The House Wren, a common, native bird all over the United States, is a small bird with a big voice that readily inhabits natural tree cavities and anything it can turn into a cavity (nest boxes, planters, shoes, yard art). Some people love this sweet little bird, and some people love to hate it. If you have one around your house, you'll notice that it sings incessantly. This is the male announcing and defending his territory. Even if you've never noticed the bird, you have surely noticed its nest - it fills cavities to the brim with small sticks and twigs. Male wrens will make numerous nests and the female chooses the one she likes, which leaves other filled-up cavities completely useless to other birds. They also intentionally fill other cavity-nests with sticks as a way to out-compete other birds in their territory, including bluebirds and swallows. Talk about tough guys.
For us humans, regardless of how you feel about House Wrens, if you have any nest boxes on your property, it's important that you fully clean them out each fall or winter so that cavity-nesting birds have a fresh start every spring. Otherwise, over time boxes will all get filled with "wren sticks" and be useless to all birds. Here's a plug for keeping your boxes clean!"