Eastern Bluebirds Using Open Cup Nests

Photo © Jason Estep

On May 24, 2017, Jason Estep noticed something unusual. A male Eastern Bluebird was inspecting an old robin’s nest above a light fixture in an open-air facility in Franklin County, Ohio. He had seen a bluebird pair in the area on previous occasions, but did not think much of it until the male appeared to start working on this old robin’s nest. Jason then monitored the nest for eight consecutive days and found, each time, a female bluebird sitting low in the nest. She appeared to be incubating!

Eastern Bluebird At Robin Nest
Eastern Bluebird At Robin Nest

A female Eastern Bluebird sits in an old nest of an American Robin.

For the next 23 days, Jason had to be away and could not monitor the nest (sometimes life gets in the way of data collection). Unfortunately, we will never know if the nest fledged or failed, or how many eggs were in it, but we do know that it was empty on the final nest check on July 11. At 25 feet high and under a roof overhang, the nest was challenging to monitor. Jason’s notes indicate that the female would step away from the nest periodically and return to it throughout the day, ruling out the explanation that she was simply using it as an overnight roosting location. However, we cannot rule out the possibility that the pair “adopted” a nest full of blue eggs (the same color as their own eggs would be) after happening upon it within their territory. Although we have heard of birds incubating the eggs or feeding the young of other species, fostering is rare. Might this have been caused by a coincidence of timing, similarity of egg color, and/or loss of their own nest?

Stranger Things

We think that Jason probably did see Eastern Bluebirds using a salvaged nest to try to raise their own young, and there are two main reasons. (1) It is the simplest explanation, and (2) Eastern Bluebirds have been documented to occasionally use cup nests. Captain S. G. Reid, writing in 1884 in The Birds of Bermuda, states about the Eastern Bluebird that “It occasionally drives the Red Bird (Cardinalis virginianus) from its nest, even after eggs have been laid, and uses it as a foundation for its own.” Reid also noted finding nests “on the branches of trees” in Bermuda. Mr. A. Sprunt, Jr. (1946) records an instance of an Eastern Bluebird nest in South Carolina which was “saddled on the horizontal limb of an oak tree.”

An Unusual Nest Site
An Unusual Nest Site

Side view of the nest repurposed by an Eastern Bluebird.

We asked Dr. Patricia Gowaty, a Distinguished Professor of Ecology and Evolutionary Biology at UCLA who has studied bluebirds in the field for 30 years, how unusual this sighting is. According to Gowaty, the frequency of open-nesting in bluebirds is incredibly hard to know. “Almost nobody studies Eastern Bluebirds in natural nests. Focusing on nest boxes means there are a lot of variations in life history that we don’t see.” Gowaty explained that we tend to canonize what we expect from bluebirds by focusing so closely on nest box results. In the book Longleaf, Far As The Eye Can See, one can find a photo of an Eastern Bluebird nest situated within a vertical burn scar on a tree trunk, on a short projection of bark. Gowaty points out that this type of nest may have been more common in the ancestral pine forests of the southeastern United States.

Don’t Box Them In

Below Deck
Below Deck

A pair of Eastern Bluebirds nested on deck supports in June 2017.

So was Jason’s observation actually rare, or has our close study of nest boxes colored our perceptions of “normal” bluebird behavior? Jason told us that the small woodlot behind the facility was clear cut last summer. It’s possible that the pair returned to their territory that otherwise had food and resources, but now lacks sufficient nesting cavities. Perhaps they exhibited the flexibility of their ancestors, before nest boxes were backyard staples.

At the time of writing, NestWatch holds 77,729 digital records of Eastern Bluebird nests. Of these, we could only find one that was similar to Jason’s. Barbara Starr had Eastern Bluebirds nesting under the deck of her Victor, New York home in June of this year. Barbara reports that it was possible to peek between the floorboards to check the nest. Although the below-deck nest was successful, the bluebirds did not attempt a second nest in this spot (there are two nest boxes on the property, which are also used).

Have you ever seen bluebirds doing something that they “weren’t supposed to be doing”? If so, tell us about it in the comments.

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21 Comments

  1. Dawn Gallo says:

    I had a pair of Eastern Bluebirds build a mest in one of my boxes. The female laid five eggs and was incubating them. There was also a wren in a nearby box. One day I discovered all the eggs gone. I assume the wrens destroyed them. I removed the wren house, but decided to leave the clean bluebird nest. About three weeks later the bluebirds returned, took over the nest and laid another four eggs. They all fledged successfully. I ‘m guessing it was the same pair. We have had bluebirds in our houses now for nine years and they have produced over thirty youngsters. So happy to be doing our part to increase their numbers.

    • Rick Barber says:

      Dawn, larger Carolina Wrens, the ones with a white bar through the eye, will not bother Bluebirds. But the smaller House Wren will, since they compete for the same nesting boxes. There are nest cam videos showing them pecking holes in eggs, and even bodily throwing nestlings out of boxes. Would love to see such a raider encounter an angry parent at the entrance some day. I’ve seen Bluebirds run off other birds twice their size, very brave and ferocious when protecting their territory.

  2. Megan Maxwell says:

    I was greatly surprised to find a bluebird nest and one egg in one of our nest boxes in October one year. We are in East Texas. Nothing came of it– maybe they realized it was the wrong time of year? It’s a mystery.

  3. Lois Masso says:

    Two years ago we had a pair of Great Crested Flycatchers use our unused Purple Martin house to build a nest and raise young. Proud papa loved to sit on the power line a few feet away and sing. I was hoping we’d see them again but they never returned. We routinely have Catbirds and Northern Mockingbirds raise young here in Central Florida each year in addition to our year-round feathered residents.

    • Susanne says:

      I had a pair of GCF’s do the same in my Purple Martin house in RI a couple of years ago.

    • Rick Barber says:

      Lois, we’ve had both Titmouse and Chickadee families raised in our Bluebird boxes before, when they weren’t being used by the intended occupants. If I see House Sparrows building though, I remove the nest as many times as it takes. This is legal since they’re an invasive species.

  4. Claudia Cliffel says:

    Years ago I took a class at Cornell to band blue birds and tree swallows. The info was a dispersal study, but Cornell lost their funding. I had to return my bands. I still have boxes on my property and they always use the boxes each year. At present there are two being used, 5 in one box and 4 in the other box. Tree swallows have already fledged.

  5. Felicity Rask says:

    Bluebirds appeared to be nesting in a cup nest under a shelter at Brent and Becky’s Bulbs in Gloucester VA – an ebird hot spot. It was too high for me to monitor for eggs or young but I saw both male and female birds on the roof and fly out from under the shelter.
    My experience has only been with Bluebird boxes but have often wondered where and what their nests are when there is no box available.
    I will inspect again tomorrow and perhaps get a photo to show the various layers of bird nests.

  6. Hope Orr says:

    This year a pair of bluebirds out-compeated a house wren for a nest box the house wrens were considering. The nest the bluebirds built was mostly house wren sticks with a small grass platform on top. There was no nest cup. The bluebirds successfully raised 4 young.

  7. Brinda Curran says:

    Earlier in the nesting season A pair of Bluebirds nested under the eaves of a picnic gazebo used by a Radio Controlled airplane club. Apparently the Bluebirds didn’t mind all the noise and conversations taking place each morning as the club members flew their model airplanes. Also of note: There was a bluebird nesting box within close proximity but it was being used by a pair of Carolina Chickadees. I watched for several minutes as the male and female carried nesting material to the location. Two weeks later I saw the female sitting on the nest. She flew off when I approached. Unfortunately the nest was built too high for me to see inside even when standing on a picnic table.

  8. Carol says:

    Western Bluebirds in San Diego County, California have been observed nesting in open-cup nests. The San Diego Natural History Museum documented this when doing field work for the San Diego County Bird Atlas in the late 1990’s.

  9. I have not heard any cases of open nesting bluebirds from our members over the last decade. However, this doesn’t surprise me. Bluebirds, like many other species can be very adaptable and surprise us with behaviors that are not common among most others of their own kind. The fact that we don’t often look for open bluebird nests doesn’t mean they don’t exist in some numbers. Like anything in nature, there are always outliers that fall outside the parameters that are established for a species.

  10. Merna Tontat says:

    I have a bluebird box that attracts them each year. I love watching a male on top of the box trying to look handsome enough to attract the lady down from the trees. Usually there would be a successful union and eggs laid and hatched. Problem is I have never seen a fledgling outside of the box although I have a film capture or two of them poking out their heads to see where dinner was. I worry about squirrels and snakes. (We do have a big black rat snake around but I don’t think it could get its head through the hole. Yes, I know there are guards but none that fit the fat wooden post. I want so much to see a fledgling. Do they up and leave the neighborhood suddenly?
    Also, is it unusual for bluebirds to use suet blocks? In spring they are busy at the suet…more than one pair…patiently waiting for a bite even though it is so awkward for them to cling onto the container.

  11. Candace Bridgewater says:

    My son’s shed in Quitman, GA had bluebird nest with young on top of a messy nest supported by deer antlers!
    I have a photo but can’t get it to stay in this box.

    • Robyn Bailey says:

      Hi Candace. You can share photos by clicking on the “Participant Photos” button on this page. That will take you to a gallery of participant-contributed photos, where you can upload yours. Thanks!

  12. Bill Read says:

    One of our bluebird members in Ontario ( Ontario Eastern Bluebird Society ) reported a pair of bluebirds using a robins nest. This was about 10 years ago. They laid eggs and incubated them for the required length of time but they turned out to be infertile.

  13. Paula Newcomb says:

    I love reading about these Eastern Bluebird nesting experiences. Out here in Sacramento, CA we have a similar bird called the Western Bluebird. I have worked for our local wildlife rehab center for many years and only began seeing our Western Bluebird come in from time to time several years age. I also began seeing them flit by in front of my car when passing the park about a block from my suburban home. Last year I put up a Western Bluebird nest box in my back yard. Right-sized hole at the right height and facing East across a lawn but next to our red maple tree and a short distance from many other trees and shrubs. Lo and behold two Oak Titmice built a nest and raised 5 young this year. I plan to clean out the nesting material and hope for bluebirds next year.

  14. Dorothy Tompkins says:

    We also had a bluebird nest on a rafter where a phoebe has usually nested.

    • Robyn Bailey says:

      Dorothy, that’s neat. Do you have any photos to share? If so, you can upload them to our Participant Photo Gallery!

  15. Felicity Rask says:

    Today I checked the cup nest at BB&B in VA and found an EABL sitting in the nest. Current Nest is built over what appear to be old Wren and Bluebird nests. Photo is available but I can’t find the photo gallery!
    Felicity Rask

    • Paula says:

      Felicity, scroll to the top of this page. On the left side, (under the prompt to sign up for the eNewsletter), there is a picture of some tiny nestlings with pink mouths and a caption: “NOW FEATURING PARTICIPANT PHOTOS AND VIDEOS…”. Select this and it will bring you to the photo gallery.

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