Posted by Mom on January 5, 2018
Way back as a youngster, I was fascinated by bluebirds. Well, any kind of bird, actually. I roamed about the woods, swamps, and fields searching for bird nests and built up a collection of nests, eggshells, and feathers. But bluebirds, now they were an almost mythical creature.
In hopes of attracting a pair of eastern bluebirds (Sialia sialis) to our yard, I encouraged (read: nagged) my parents to set up some nest boxes. Although we saw a male bluebird sporadically for a day each spring over the following years, no pair ever set up residence in our nest boxes. Not that the boxes were empty, house wrens and tree swallows took possession, and for a budding naturalist, provided many opportunities for observation.
Fast forward a few decades and now I am the parent with three little naturalists and another chance to attract bluebirds to a country property. While in University, and dreaming about future bluebird glory, I had picked up a book about bluebirds. I cracked it open once more to see what I could do to fulfill that dream. I followed the advice, set up the next boxes and waited. Just as happened with my parents, we had brief bluebird sightings, but none chose to stay.
We speculated, and later confirmed, that house sparrows were preventing the bluebirds from taking up residence. For me, there is no love lost for these sparrows. Native to Eurasia, house sparrows (Passer domesticus) were intentionally released in New York City to control the caterpillars of the linden moth in 1852. Now these birds occur across North America; not being confined by international borders, their range spreads from the subarctic all the way to southern Panama. The birds are so adaptable and quickly colonize new territory that of all wild birds, the house sparrow is the most widely distributed bird on the planet. In all honesty, the sparrows are not to blame, they are generalists and thrive amid human habitation. We humans introduced them to a brand new continent and proceeded to lay out the welcome mat as our farms and cities spread farther west and north across the continent.
Their success at global domination has earned the house sparrow a bad reputation. The bird is considered a pest and threat to native bird species. House sparrows prefer to use tree cavities as nest sites (though they seem to find gaps between letters in storefront signs to be a wonderful alternative) and are in direct competition with other cavity nesting birds, such as bluebirds. Neither bird actually does the excavating, they leave that to the woodpeckers, who create a new nesting cavity each year, leaving the vacant cavity of last year available. These vacant cavities are a hot commodity, and with their tenacious, bully-like qualities, house sparrows come out on top wherever they compete with native birds (you can find some gruesome images online of bluebirds and swallows pecked to death by aggressive house sparrows). Well-meaning humans erecte nest boxes to encourage wild birds, but often these boxes are suited exactly to the house sparrows taste: ready-made homes close to human habitation.
At our country home, we have neighbours with a farm and several outbuildings, including a run-down barn. This property is the source for our neighbourhood house sparrow population. Come winter, a noisy flock of house sparrows descends on our bird feeders. When the weather warmed in spring, the flock breaks up into breeding pairs, and in short order, unwanted tenants look to move into the nest boxes we’ve set up.
We have several nest boxes with the 1½ inch entrance hole that bluebirds prefer. House sparrows prefer that size of entrance hole too. My first attempt to deter the sparrows was to cover the entrance holes with duct tape. While effective, the sparrows only waited for the tape to come off, which it did when the tree swallows arrived looking for nesting sites. My next attempt was to remove a sparrow nest from the box, but this only stimulated the male to turn on his neighbours in a revengeful rampage that resulted in all the nestlings in a tree swallow’s nest being killed by the irate male sparrow. In a desperate third attempt, my husband grabbed his pellet gun and shot at the males as they sat atop the nest boxes. None of these methods succeeded in deterring the house sparrows; so I turned to the internet to show me a way to keep the house sparrows from our nest boxes.
I found the website Sialis.org to be loaded with suggestions. On it I learnt that house sparrows spook easily and an effective way to prevent them from nesting in a nest box is to use monofilament (fishing line) attached to the nest box to “scare” them off. By affixing it to the roof of a nest box in an X pattern, the sparrows will not perch on top of the box, something they do to announce that they have claimed a nest site as their own. The monofilament can also be dangled from the corners of the roof so they hang next to the entrance hole (weighed down with a nut or washer so it won’t become entangled in the entrance hole and harm any occupants) and make the sparrows too leery to enter the box. Furthermore, the monofilament can be strung around the entrance hole in a square shape that will also deter house sparrows from trying to enter the nest box.
I can testify that the monofilament worked! The first year we tried it, We did not have any house sparrows using our nest boxes. Instead, each box was the home to a family of house wrens, tree swallows, or, drum-roll, please, … eastern bluebirds! Apparently the bluebirds were waiting for us to fix the house sparrow problem.
Bluebird glory was finally achieved! Our next dream is to entice purple martins to our property. Dad is already working on their apartment complex. But a challenge awaits… house sparrows like to set up residence in the same apartments as purple martins. Sigh! The battle continues…