Know Your Enemy

Being a bluebirder isn't all about beautiful blue eggs and the loving parents who raise them. It is also about predators and parasites and bad weather and worry and work. Some of the work involved in caring for bluebirds is downright ugly. This post is about the dark side of bluebirding, and if you are particularly sensitive, you should skip it altogether.

Public Enemy Number One for a bluebirder isn't mites or cold weather or pesticides or Sharp-shinned Hawks or global warming. The worst thing a bluebirder has to deal with is the House Sparrow.

female HOSP in Florida

The House Sparrow (HOSP) is not a native North American bird. It is not even a true sparrow, but a variety of finch. It was imported, along with the European Starling, by some well-meaning but ignorant people in the late 1800's. It quickly spread throughout the USA, and can now be found anywhere there are human beings. It is a cavity nester, though it can nest in the open if there are no cavities available, and its aggressive and prolific breeding habits are what make it a bluebirder's worst nightmare.

House Sparrows overwinter, and often use bluebird boxes to roost in. They are there before the bluebirds return (in areas where bluebirds migrate for the winter) and so get the jump on prime housing. They can have three broods in a season, with an average of 5 eggs per clutch, so they reproduce at an extraordinary rate.

In their zeal for obtaining nesting sites, HOSP will intimidate and chase off native cavity nesters, or will usurp active nests, breaking the eggs, killing the young, or even killing the adult birds who are trapped inside the nest box while protecting their family. It is this behavior which earns HOSP the label of "evil," although, in fairness, they are only acting according to their own nature.

The male HOSP is pretty easy to identify, especially in breeding season, with its black bib and its incessant "cheep, cheep, cheep"ing. The female can be a challenge for some people, being a plain "little brown bird."

male HOSP, nonbreeding upper,
breeding lower right, from Sibley

female HOSP, from Sibley

House Sparrows compete with our native cavity-nesting species, like Eastern Bluebirds, Tree Swallows, chickadees and titmice, for suitable nesting sites, which already limited by human intervention. They fill up a nest box quickly, with their messy weaver finch style nests, a huge ball of grasses, feathers, and trash, with an opening on the side. Knowing the difference between the nests of native birds and House Sparrows is an important thing when you begin monitoring bluebird boxes. Go to The Birdhouse Network, a branch of Cornell's Lab of Ornithology, for everything you could ever want to know about our native cavity nesting birds.

beginning of a HOSP nest

If I let the above nest go, it will soon look like this:

So, what do we do about House Sparrows? Number one, if you can't manage them, don't put up nesting boxes or decorative bird houses and let them become infested with HOSP. If you aren't part of the solution, you are part of the problem.

Number two, alter your bird feeding habits to discourage HOSP. Stop feeding cracked corn, don't put out bread, cereal or old donuts or baked goods, which attract them. Offer black oil sunflower, Nyger (thistle) or safflower seed. While HOSP will eat anything, they are less attracted to these seeds.

Number three, if you have nest boxes for cavity nesting species like bluebirds or Purple Martins, don't let HOSP nest in them. Tear out their nests daily (throw the nesting material away in the trash; if you throw it on the ground, the HOSP will just re-use it) or block the entry holes until your desired species are back and looking for housing.

For additional protection, use a "sparrow spooker" on your bluebird box. After the female bluebird has laid her first egg, attach this device to the box to discourage HOSP from entering the box and destroying the eggs, killing the nestlings, or even killing the adult female bird as she tries to protect her young.

A "sparrow spooker" can be a homemade device, like mine below, made of wooden dowels and old Mylar banners, or you can purchase one ready-made these days. You can find more about Sparrow Spookers at the Sialis web site, here. They work because once the female bluebird is bonded to her nest site, she will continue to use that box to lay the rest of her clutch and incubate her eggs, despite the weird addition. House Sparrows, with their extremely suspicious natures, will avoid them. It will NOT work if you put it on before egg-laying, so don't try it. You will spook your bluebirds, too.

"sparrow-spooker" mounted on nest box

Looks like trash, but it works.

I have only used spookers with bluebirds, not with Tree Swallows or chickadees, so I have no idea if they would work. My Tree Swallows nest in gourds, which HOSP are less likely to use (though they will if they have to) and I find TRSW to be much more aggressive in protecting their homes from HOSP. Chickadees, being much more easily frightened, might not return to a box with a spooker attached. You can use nest boxes with smaller holes (1 1/8" diameter) to protect chickadees, since they can enter but HOSP cannot.

bluebird box, complete with
sparrow spooker and pole guard

Until a few years ago, I practiced a "live and let live" policy when it came to HOSP. I didn't let them nest in my boxes, I discouraged them from coming to the feeders, but I didn't actively pursue them. I even bragged on Purple Martin web sites about how I was "protecting my karma" and practicing "no-kill" sparrow control.*

Then, tragedy struck. A male HOSP decided he wanted the nesting box where my resident bluebird couple had just started their second clutch of the season. He entered the box and destroyed their three eggs. I cleaned out the box, and the bluebirds tried again. Again, the HOSP returned, destroying two more eggs. My bluebird couple left me. The HOSP didn't use the nest box. He just killed five potential bluebirds, without even needing the box for his own family.

That was it. I was converted. Now, I actively trap and remove HOSP, using in-box traps like the ones below:


These traps are mounted inside the front panel of the nest box, with the hole lined up with the box's entry hole. When a HOSP enters, the trigger is tripped and the HOSP is trapped in your nest box. A red or orange flag covers the hole, and signals to you that a bird is trapped inside. The wooden trap, on the right above, may not be as effective with a wary male HOSP, since it makes the entry hole thicker. The metal trap, with its slimmer profile, sometimes works better.

Sometimes, HOSP try to nest in my metal martin housing.

There is a special Spare-O-Door to use with this type of box, which works the same way as my insert traps. **



Only use nest box traps at a time when you are available to monitor hourly. You must be quick to release any native bird you catch by mistake, and you must be humane about removing the HOSP as soon as it is caught, rather than letting it suffer and die a slow death inside the trap box.

Once the trap is tripped, I put a large, clear plastic bag over the entire box and open the door. (Spare-O-Doors come with their own tool for removing the bird.) Most HOSP fly out of the box immediately and flutter around in the plastic bag. Most native birds huddle in the nest box, peering out. Once I am certain I have identified a HOSP, I euthanize it. (If you are not sure whether you have a non-native female HOSP or a native bird, RELEASE IT!) If I have caught the female, I reset the trap, since the male will still come back. If I have caught the male, I clean out the old nesting material and remove the trap, since the female will abandon the site.

Do I enjoy trapping and killing House Sparrows? No, I absolutely do not. It still makes me sick every time I do it, but it is a task I have decided I must undertake, for the sake of my bluebirds. As a bit of consolation, I turn over the bodies of my victims to RAPTOR, Inc., to feed Cooper's Hawks. It helps me to reconcile myself to this odious task.

My reward for all this trapping?

This:

female Eastern Bluebird leaves her nest,
where she has 5 lovely eggs awaiting hatching,
due in about 10 days.

* For more information on lethal vs. non-lethal House Sparrow control, including some very graphic photos of bluebird damage, go to the Sialis web site here.

** For traps, go here to the Van Ert site or here to the Purple Martin Conservation Association's Martin Market Place.