I learned early in bluebirding how to ID nests of different cavity-nesting species. Bluebirds are easy to ID. They build tidy, clean nests (at least those I’ve seen on my trail, which is the Eastern Bluebird) of either soft grasses or pine needles, depending on habitat close to their chosen nesting site, and create a perfect cup for the egg laying. Our other native birds have a variety of materials and nesting behaviors I have learned to look for to ID the species. After having some experience, I know the species without seeing eggs. For instance, our Carolina Chickadee (CACH) is easy to ID by using plenty of mosses first and then layering on top with more materials, including plenty of animal and plant hairs and fibers. The Tufted Titmouse (TUTI) will also use mosses as well as the Carolina Wren which intertwines mud and dead leaves in the mosses. If I’m not sure on a nest what the species is, I wait for the eggs to arrive to ID for sure, as the eggs are distinct in markings and color.
We should never allow this species to reproduce in our nestboxes designed for our native birds. To help new bluebirders to know what to look for to ID the House Sparrow nest and eggs, I’ve included a few photos below of the two nests removed. This is the ONLY sparrow species (it’s not really a sparrow–the House Sparrow is actually a Weaver Finch) that are causing havoc for our native birds. This is the only site on my trail that I HAD a House Sparrow problem starting with a 1-holed box. The 1-holed box (with an existing HOSP problem) was replaced by a 2-holed test box which (over the course of the test period) solved the problem without the need to trap out HOSP. The 2-holed box test was a success and I haven’t had any sign of HOSP for over a year. When I removed these nests and eggs of this invasive species, I conserve them for educational purposes (such as displays and for photographs). Remember, the House Sparrow is not protected by law so it is legal for me to remove those nests.