More natural insect control. I built this little nest shelf out of scrap wood and tucked it under the pole barn. It took about 3 days before the wrens found it and built a nest. The Carolina wren is a great bird around your house and garden. They won't eat your tomatoes, but they will eat the caterpillars and other insects that want your veggies. This nest produced 3 new wrens this spring. They will nest in almost anything and don't mind being near humans.