House Sparrows, which are a non-native species, has done serious harm to our cavity-nesting native birds such as bluebirds, chickadees, nuthatches. These exotic species destroy nests, eggs and nestlings of these native species in order to take over nest cavities they have already occupied. They are so aggressive they even kill the adult birds.
Several websites including the Cornell Lab of Ornithology and the North American Bluebird Society explain methods, both active and passive, to control House Sparrows . But the passive methods are only really applicable to artificial nest boxes. And some are reluctant to use the active control method of trapping even though only humane methods are recommended and described.
So I was very impressed when I saw a photo showing an innovative method of keeping House Sparrows out of a natural nest cavity that Nanci St.George and her husband devised. Nanci, who posted this on the Great Backyard Bird Count facebook page, wanted to help out some chickadees that were excavating a nest hole in a tree in their yard.
I thought this was a great idea that ought to be shared widely as others. So I asked Nanci if I could use their idea and photos for this blog and she agreed.
Nanci told me, “It’s a piece of plywood with a 1 1/8″ hole (or a little less) which is what is recommended for Chickadee size. My husband guessed how deep the hole in the tree was so that he could screw the cover on below the hole as to not harm the Chickadees once inside. Two screws in the bottom, one in the top and voila!”
This is such a wonderfully simple method though it is limited to nest cavities that birds have already excavated or done a lot of excavation on. If you try it, be sure to follow her husband’s example by estimating the hole depth so you can put the screw in so that it does not project into the nest cavity where it could harm the birds or their nestlings. One idea I had would be to drop a piece of string with a small weight on the end of it into the nest cavity to help judge the depth. And be sure to check the recommended entrance hole size for other cavity nesting species
Nanci observed House Sparrows trying unsuccessfully to enter the fortified hole that was now too small for them to enter. And she was pleased that the chickadees returned to claim their ‘home’ as shown in these photos. But do understand that some birds might not return and it’s a good idea to use this only when there is a serious threat to native species from House Sparrows trying to enter a cavity being excavated or a serious problem with House Sparrow in the area.
I wonder if this will also work at excluding Starlings from natural nest cavities? If someone tries it for Starlings, please let me know.