You look out your window around springtime and notice something very strange. It looks like two male house sparrows have gone into the nest box. They’ve got the same coloring, same beak, same patterns – it definitely checks all the boxes.
If you live in certain areas in the US, particularly St. Louis, MO, you didn’t see two male house sparrows in your birdhouse, you saw its invasive cousin, the Eurasian tree sparrow.
The Eurasian tree sparrow looks like a house sparrow and both are introduced species to the US. There are distinct features such as a dot on the cheek and a full chestnut colored cap that can help you tell the difference. And both male and females have the same patterns.
The Eurasian tree sparrow has only flourished in very isolated areas of the United States and are most abundant in the St. Louis area, but have been spotted as far north as Canada.
According to the Migratory Bird Treaty Act of 1918, the act does not apply to old world sparrows of the Passerine family. Therefore, the MBTA doesn’t apply to house sparrows and Eurasian tree sparrows, and any other old world, introduced Passerine bird (US Fish and Wildlife Service, 2020).
Even though the Eurasian tree sparrow is not covered by the MBTA, we know from people in our network that they are protected in Illinois.
How to tell the difference between Eurasian tree sparrows and house sparrows (English sparrows)
When you first get started with sparrow control, it is very hard to tell the difference between male house sparrows and Eurasian tree sparrows, and we’re often only alerted of the difference when an odd behavior happens around breeding season. But here we have a table of differences to help you differentiate house sparrows from Eurasian tree sparrows as well as a diagram pointing out the differences.
| Feature/ Location | House Sparrow | Eurasian Tree Sparrow |
| Crown | Gray top crown | Chestnut/brown top crown |
| Face | Slight mask at the eyes and chin | Slight mask at the eyes and chin |
| Face | Gray cheek, plain | Gray cheek, dot |
| Breast | Black bib | No bib |
| Sexual differentiation | Males look different from females | Males and females look the same |
Eurasian tree sparrow competition and aggression level
Because Eurasian tree sparrows are quick at claiming a birdhouse and building their nest, they are often able to outcompete native cavity nesters in that respect. In two or three days, a claimed nest box will be filled to the very top with nesting material.
Like the house sparrow, Eurasian tree sparrows aren’t terribly particular about nest box features, nor are they very particular about nesting material. Both types of sparrows will grab wads of different material types, including trash.
They also both have similar nest structural strategies, forming a tunnel in the nest rather than a normal nest cup.
In terms of aggression, Eurasian tree sparrows are very persistent about occupying a nest box, even if there are birds living in it.
We have also observed them to have attacked occupied nests, including chickadees, house wrens and bluebird nests. Literature out there is limited. Most claim they do not attack. But we have noticed them at least raid nests when parent birds are away foraging for food.
We have a more detailed article about Eurasian tree sparrow aggression and behavior.
The house sparrow, on the other hand, will enter birdhouses they’re curious about and attack nestlings and adult birds, killing them for the nest box.
Reasons the Eurasian tree sparrow is not as widespread as house sparrows
One of the most cited reasons Eurasian tree sparrows have not become as widespread as the house sparrows is because of the aggressive nature of house sparrows, which Eurasian tree sparrows cannot outcompete.
This may be partly true. However, we have observed both species colonizing an unmonitored purple martin box. Another very important observation is that we have seen house sparrows to be more human tolerant, nesting in commercial areas like store signs, and outdoor rafters.
What we believe, based on this last observation is that the house sparrow’s ability to nest in heavily populated, commercial locations is another huge contributor to their success over other birds.
Ways to deter Eurasian tree sparrows
Because Eurasian tree sparrows are so similar to house sparrows, most of the usual methods for deterring house sparrows will work on Eurasian tree sparrows:
- Monofilament line on birdhouses
- Sparrow spookers on nest boxes
- Avoiding cheap seed with millet or bread
Those are some ways to deter Eurasian tree sparrows.
However, one important thing to note is that we have observed them eating Nyjer finch seed from a finch feeder. They often come in large colonies to a finch feeder. This is unusual since house sparrows are not as interested in Nyjer seed.
Because they’ll eat Nyjer, we recommend taking down finch feeders during nesting time so that you do not attract these birds to your nesting sites.
Video Comparing House Sparrows and Tree Sparrows
References
US Fish and Wildlife Service. (2020). Final list of bird species to which the Migratory Bird Treaty Act does not apply. Federal Register, 70, 12710-12
