Just the mention of the House Sparrow (Passer domesticus) in the world of Bluebird nest monitoring sends shivers down the back of some trail monitors, and rightfully so. There is plenty of documentation of House Sparrows attacking Bluebirds and other cavity nesting species, killing both young and adult birds (see my friend Bet Zimmerman’s page here).
You see, the House Sparrow is a non-native species, introduced in North America from England in 1851. Being a non-native species, it is not protected by the Migratory Bird Treaty Act and yet this bird has become the most widely distributed bird on the planet1.
Native range in dark green and introduced range in light green
The problem is that House Sparrows are cavity nesters and compete with native cavity nesting birds in North America for breeding sites. Luckily, I have not had a problem with them on my bluebird trails but many monitors have, especially in the mid-west and Eastern U.S. (see the North American Bluebird Society’s page on House Sparrow control).
Crossing a bridge over the Sacramento River recently, I saw a flock of birds on the railing out of the corner of my eye as I drove over the bridge. They didn’t look like the Cliff Swallows that always nest under this bridge.
I pulled off the road and parked below the bridge where I found a rather large colony of House Sparrows nesting under the bridge in Cliff Swallow nests. House Sparrows are known for using and even usurping nests of Bluebirds, Purple Martins, Barn, Bank and Cliff Swallows.
It certainly surprised me to see these Cliff Swallow nests with House Sparrow heads sticking out of them and females feeding their young.
This video shows the females feeding young in several of the Cliff Swallow nests under the bridge and the male claiming nests by sitting in them.
The irony of the whole thing is that now the House Sparrow is declining in it’s native home of Europe and Great Britain1.