Of Slot Boxes and Wooden Eggs – Deterring the House Sparrow
The House Sparrow is perhaps the most adaptable and prolific bird species on the planet. Often called English Sparrow, its scientific name Passer domesticus is Latin for small, active bird belonging to the house. It is native to Europe and has spread to all corners of the world. Its adaptation follows human civilization. Where there are people, there are House Sparrows.
House Sparrows are about six inches in length and are cavity nesters. They are about the same size as Eastern Bluebirds and Tree Swallows. That’s why they all compete for nest boxes. Make sure your boxes have an entry hole no larger than ONE inch in diameter. If larger, another invasive, non-native, European bird, the European Starling, will invade the box.
The House Sparrow is Not Native to North America
This bird is not native to North America. It is an aggressive species that will take over the nesting sites, territories, and food sources of native birds. Therefore; it is an invasive, non-native species that is very difficult to manage. For a more detailed description of the bird go to this link at the Cornell Lab of Ornithology.
House Sparrows Attack and Kill Native Nesting Birds
Some years ago, I opened one of our nest boxes to find a House Sparrow sitting on her eggs. She quickly flew away. Something was unusual. She built her nest on top of a Tree Sparrow nest. I removed the aggressor’s nest, tossed it on the ground and crushed the eggs. Underneath the nest was a dead female Tree Swallow. Her head had been crushed in by the attacking beak of the aggressor. The Tree Swallow’s eggs were still intact. How horrible a death.
For more information on House Sparrow attacks and management of this invasive, aggressive bird, visit the Sialis website, they have much more detail.
Identification of House Sparrow Nests and Eggs
Their nests are easy to identify. They always have a “dome” or roof over the nest and they always have feathers in them.
The presence of the dome, in a nest box, is a tell-tale sign that it is the aggressor’s nest. The nest material is rather “trashy”, made up of all kinds of material including various feathers.
The eggs are dark brown and white speckled.
How to Save the Lives of Native Cavity Nesting Birds
We continue to learn . . . after decades of monitoring Blue Bird boxes, I have the following conclusions about saving the lives of our native birds from the murdering, aggressive, non-native House Sparrow. If you find the aggressors nesting in your nesting box try these techniques.
- Move the box away from House Sparrow infested areas. This is the best solution.
- Trap and destroy House Sparrows. Yes, there are some ethical issues here. Go to the Sialis website for details.
- Remove House Sparrow nests with eggs and destroy them. Very effective but time-consuming.
- Replace House Sparrow eggs with wooden ones. This may work the first year but they figure it out.
- Put up House Sparrow resistant nest boxes like the Hughes Slot Box. Details follow.
Replace House Sparrow Eggs With Wooden Ones
If you find a dome-shaped, trashy nest with eggs in your nest box, carefully take out the eggs and replace them with similar-sized eggs made out of wood. The parents will sit on them possibly the first season and never hatch a single one. However, the aggressors will eventually figure it out and one study conducted by Sparrow Swap concluded that this technique will delay House Sparrow egg-laying by about ten days.
Try a Slot Box to Deter House Sparrows
Another way to deter the aggressors from nesting is to put up nesting boxes they don’t like such as the Hughes Slot box. House Sparrows prefer a deep box because they build the dome. A shallow box prevents them from building the dome and the slot gives native birds an escape. Click here for a Hughes Slot Box design.
Hopefully, your nest boxes will be occupied by our native birds such as Eastern Bluebirds, Tree Swallows, and Carolina Chickadees.
© Robert N. Whitescarver 2017, updated April 5, 2020.