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How are people managing invasive birds at nest boxes?

Photo © Allen Wilkinson

In 2018, NestWatch circulated a survey to investigate how many people had experience with non-native birds in their nest boxes. We were interested in finding out peoples’ knowledge of House Sparrows and European Starlings, and their attitudes towards managing them, especially if people encountered these non-native birds in the nest boxes they monitor. We are pleased to report that the findings have now been published online.

Witnessing Competition

We received 871 fully completed responses from NestWatchers and other people who monitor nest boxes. Nearly one-third of the respondents (30.3%) reported having witnessed a House Sparrow or European Starling usurping the nest of a native bird in 2018. In this context, usurping means to take over an active nest, causing it to fail. The people who witnessed this reported varying levels of competition by species. The two species which were most impacted by this competition were Northern Flicker (35.3%) and American Kestrel (23.0%), both of which are experiencing widespread population declines. In our study, sample size was small for Northern Flickers, but another study of natural cavity nests found that European Starlings were the largest source of nest failure for flickers (Tomasevic & Marzluff, 2017). Multiple sources of evidence suggest that competition from invasive species is a problem for flickers in both natural nest sites and nest boxes (at least in urban populations where starlings are most abundant). American Kestrels can sometimes outcompete starlings for nest cavities (McClure et al. 2015), but our nest box data revealed that kestrels are not always the winner. Unfortunately, it is not yet possible to exclude starlings from boxes made for Northern Flickers and American Kestrels because starlings are similar in size to these two vulnerable species.

Chickadees (all species combined) were the third most-impacted species, at 16.5% usurpation. Since they do not migrate, and because they are smaller in body size, chickadees may be in direct conflict with House Sparrows as these species seek out the same size nest cavity at the same time of year. For bluebirds (all species combined), 9.3% of nests were usurped, predominately by House Sparrows (starlings not being able to fit in standard bluebird boxes). We suspect that the usurpation rate is lower for bluebirds because more people are proactively managing for bluebirds, which are a beloved and iconic species.

Nest Usurpation Varies By Species

Nest Usurpation Varies By Species

Proportion of nest attempts by native host species usurped by non-native European Starlings and House Sparrows. Asterisks above columns indicate that House Sparrows and European Starlings usurped nests at statistically different levels; no asterisks indicate similar levels of impact from starlings and sparrows. Nest samples: n = 3,156 bluebirds; n = 1,468 Tree Swallows; n = 412 Purple Martins; n = 81 American Kestrels; n = 439 House Wrens; n = 19 Northern Flickers; n = 164 chickadees; n = 37 titmice; and n = 46 Bewick’s/Carolina Wrens.

Management Behaviors

Just over a third of our survey respondents reported that they did not manage for invasive species in 2018 (36.9%). But of those who did, eviction and repelling techniques were the most popular (e.g., removing nests, removing eggs, reducing entrance hole sizes, using Sparrow Spookers, etc.). Of those who managed their nest boxes actively (as opposed to preemptively), 33.4% were willing to trap and euthanize invasive species. Because removing nests and eggs may actually increase nest site takeovers if sparrows simply relocate to the nearest occupied box, this finding highlights the need to develop more effective non-lethal management techniques.

House Sparrow Egg Management

House Sparrow Egg Management

Nest monitors may choose from several methods of managing invasive species, from removing nests and eggs to euthanasia.

Our data reflect that the biggest difference between nest monitors who manage against House Sparrows and European Starlings (using any technique) and those who don’t comes down to whether or not they witnessed the failure of a nest that was taken over by either a starling or a sparrow. That is, those who experienced a takeover were 9.6 times more likely to manage than those who did not witness this in 2018. Additionally, the higher the respondent ranked the overall threat of non-native species to native birds, the more likely they were to manage invasive species. Interestingly, NestWatch participants were nearly twice as likely to take management action as non-participants, perhaps because of the desire to avoid reporting this type of failure. Gender, age, number of nest boxes, and number of years’ experience did not influence whether or not people managed their nest boxes to avoid usurpation by non-native species.

Key Takeaways:

  • Although our results only reflect nests in boxes and cannot speak to natural nests, competition from non-native species was evident across nine species groups: Northern Flicker, American Kestrel, Purple Martin, Tree Swallow, chickadees, titmice, House Wren, Bewick’s/Carolina Wren, and bluebirds.
  • Nest box monitors are engaged in a variety of management tasks that can support the nesting success of native birds. Non-lethal techniques are more popular, and need to be evaluated for their long-term efficacy.
  • NestWatch staff will be updating the data entry site to better record when a nest has been taken over by another species. Participants will soon see a new outcome option, and the ability to specify which species has taken over an active nest (including instances where native birds have taken over another native species’ nest).

NestWatch staff would like to thank all of the respondents who shared their experiences with us through the survey. Your responses give valuable insight into the social aspects of current ecological issues. Thank you!


References:

  • Bailey R. L., H. A. Faulkner-Grant, V. Y. Martin, T. B. Phillips, and D. N. Bonter. 2020. Nest usurpation by non-native birds and the role of people in nest box management. Conservation Science and Practice 2020: e185. https://doi.org/10.1111/csp2.185
  • McClure C. J. W., D. M. Hilleary, and D. P. Spurling. 2015. American Kestrels actively exclude European Starlings from using a nest box. Journal of Raptor Research 49: 231–233.
  • Tomasevic J. A., and J. M. Marzluff. 2017. Cavity nesting birds along an urban-wildland gradient: is human facilitation structuring the bird community? Urban Ecosystems 20: 435–448.

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28 Comments

  1. Michele says:

    I have sparrow problems a lot of people do. I have tested many things and what works best for me is I have a wren guard on my bluebird Xbox that I don’t ever take off I just lower it down into position slowly each day and they get used to it and I also use the spooker on top and keep them kinda long and with time attach them to the bottom of wren guard after at least one egg is in nest.With my tree swallow box I just put on spooker and attach pieces on the roof also so they move a lot around the entrance hole only after a nest is built do I attach the extra pieces and placement of boxes is also very important ! And I also trap a lot or none of these things would help.

  2. Marcia says:

    Seems like a lot of work and worry. Why not just move the box to their natural habitat?

  3. Ann Knudson says:

    I have lost numerous nests, mostly tree swallows, to house sparrows. One week I’d check the nestbox, and there’d be six white eggs and a bright blue parent sitting on the eggs or swooping at my head. The next week, those eggs would be missing or smashed on the ground, and there’d be a house sparrow nest on top of the old tree swallow nest, sometimes built on top of a dead parent swallow with its head pecked to bloody ruin. Spookers didn’t work for more than a a few days. The sparrows quickly got wise to them. I now trap and kill house sparrows that invade occupied nestboxes. I also try to place nestboxes at least 200 yards from the nearest occupied building, better yet a mile or more away where possible. “Location, location, location” counts for birds as well as humans. In my experience, house sparrows are literally HOUSE sparrows. They don’t like empty fields, pastures or marshes nearly as well as they like being near buildings with people. Tree swallows, house wrens, and eastern bluebirds are perfectly happy out in the boonies. Give tree swallows flying bugs, give house wrens trees and shrubs, give bluebirds short grass (grazed or mowed), and they’re happy.

    Location is not a 100% fix.. House sparrows can and do take over nestboxes well away from any building. It does, however, improve the odds of a successful nest by native birds.

  4. tony says:

    Apologize up front if this offends anyone but, after weighing everything, I have come to terms with this process. I have 10 bluebird houses which give the birds plenty of options if their nest is taken over by HS. If a sparrow begins to nest I wait till night time to capture and euthanize the adult and feed the eggs to my dog. Sparrows killing bluebirds while they sit on their eggs is a gruesome thing to discover. I also have a sparrow trap located close to my purple martin house which I check several times a day in case a native bird gets caught.

  5. Marcia says:

    Excellent. Best practice. Couldn’t agree with you more on habitat choice. We should not be placing boxes in areas not native to the species. Now, if I have a house sparrow on a nest of eggs in a box next to a box that has a bluebird on a nest of eggs in it, I never remove the house sparrow nest without capturing the house sparrow. The sparrow is ruled by his hormones at that time of year. He will anger and fly to the bluebird box and kill the bluebird if I remove the nest. My goal is to keep the sparrow calm. If I can’t remove the sparrow, I will use any of the methods to “damage” the eggs. The female will then sit on the eggs for 2 weeks allowing the bluebird to survive. At two weeks, the house sparrow will often move on or lay more. While the house sparrow is occupied with those, now infertile, eggs, I place a sparrow spooker on the bluebird house. It has never not worked. Also, if I get a question from someone who has one box in his or her yard and a bluebird and house sparrow are fighting over it, again I want a calm sparrow. I ask them to immediately put up another box on the opposite side of the yard. The house sparrow and bluebird will split and choose their own box. They don’t want to be angry. It uses too much energy. Then, I repeat the above steps. On my trails, I’ve learned that it is best to try to understand, not fight, the birds and predators in order to be successful and the successes do come as you clearly show.

  6. Peggy Conroy says:

    what is the best sparrow trap and how do you euthanize the sparrows? Does this practice produce more sparrows? Often populations explode when stressed.
    I’ve found that leaving the sparrows a couple of nests keep them from pecking the bluebird and tree swallows to death.

    • Holly Faulkner, Project Assistant says:

      Hi Peggy, Please check out our Managing Invasive Species page for tips on how to legally manage invasive species at your nest boxes. We do not have any product recommendations, but you may want to talk to your state’s wildlife office for advice.

  7. Pat says:

    I have not put up a Flicker/Kestral box because I am concerned I would just be feeding my larger hawks, owls, and foxes. But I do have a suet feeder on a tree that the flickers usually defend from Starlings. The Flicker waits until there is a cluster of Starlings on the feeder, then the Flicker comes up below them and attacks their toes. Obviously the Flicker does not like Starlings, it does not do this to other birds at the feeder.

  8. Mark says:

    I have had good success with bluebird nesting in my yard ever since I stopped using a bird seed feeder during the winter. With no bird seed around for several years, the English sparrows have vanished. I now have re-started feeding seed, but am monitoring closely. If house sparrows appear, I will stop feeding again.

  9. TheSmiths says:

    Peggy Conroy, you may be interested in this article by the Purple Martin Conservation Association, https://www.purplemartin.org/uploads/media/27-2-humaneeuthanasi-749.pdf and this article by Elizabeth Zimmerman Smith at Sialis.org http://www.sialis.org/hospdispatch.htm .

  10. Scott says:

    Trapping is effective. If just using deterrents alone the House Sparrows will still increase in numbers. Keep up the good work removing them and please encourage others to do the same. There are plenty of videos of House Sparrow attacks to be convincing of the need,and change the minds of those who are sympathetic of these invaders.

  11. Brine Blank says:

    If an invasive species is destroying natural populations I’m no sure why every loses their minds over ‘lethal reductions’ of said species…isn’t that the only logical way to truly stop their spread and destructive behaviors…

  12. Chuck says:

    Having to find Tree Swallows with their heads pecked off and a sparrow nest built on top of the decapitated Swallows, prompted Me to purchase a Sparrow trap. Trapping, and dispatching the House Sparrows seems to Help out the native Birds. Please be advised. If You do consider trapping House Sparrows, please don’t release them someplace else. You will only help this invasive species gain a foothold elsewhere.

  13. leonard kite says:

    house sparrows have taken over my feeders in bunches of 50 or more, I never get any tufted titmouse, cardinals, or none of the favorite birds I used to get at the feeder. I must say that i have stopped feeding this winter 2019-2020 because the house sparrows eat everything as soon as I put it out. They are flying pigs.

  14. Michael says:

    Don’t forget about House Wren and Red-bellied Woodpecker. Just as “evil” if not more so!

    • Holly Faulkner, Project Assistant says:

      Hi Michael, House Wrens and Red-bellied Woodpeckers are federally protected species and so we do not recommend any of the above-mentioned management techniques. That being said, if you’re having trouble with House Wrens, we recommend placing your boxes away from wren habitat – they like the scrubby, bushy areas along the edges of forests.

  15. Leo Jones says:

    We aren’t going to get rid of house sparrows or starlings from the USA. Whilst they may compete with native species for nesting sites etc. I don’t see any evidence that they are pushing native species into extinction. I understand perhaps evicting them in individual cases, but the all out “we must kill them at all costs” attitude is misplaced and pointless. These creatures have their own lives that are just as important to them as ours is to us, and are just as beautiful and fascinating as any other bird. We may as well get used to living with them and appreciate them for what they are.

    We’d do a lot more good for bird populations by controlling the numbers of domestic and feral cats.

    I’m a biologist, bird bander, lifelong birdwatcher, and maker of thousands of bird houses.

    • Holly Faulkner, Project Assistant says:

      Hi Leo, We agree, feral cats are a large problem for birds. You might be interested in reading a paper that came out last September on the decline of nearly 3 billion birds since the 1970s, co authored by some folks here at the Cornell Lab. In the study, they cite the largest contributors to the decline in bird species, and cats are second on the list, behind habitat loss which is the top cause for bird declines.
      The research we mention in the post above studied only peoples’ self-reported knowledge of House Sparrows and European Starlings, and their attitudes towards managing them. We received a wide range of responses, including on management techniques, both lethal and non-lethal, and this led to valuable insights on the social side of this particular issue. On our Managing Invasives Species page, you’ll note we suggest several legal management techniques should our participants decide to manage their boxes.

  16. thegbird says:

    I agree.

  17. thegbird says:

    I mean I agree with Leo Jones

  18. Monty Martin says:

    I use Van Ert inbox house sparrow traps. I have six, so I can deploy several at once. I do not wait until “something bad” happens. Once a house sparrow is attached to a box, the trap goes in. Once he is captured, I place a mesh laundry bag with a drawstring over the entire box, open the door, let him fly out. I put my hand into the bag to grab him. Once he’s out of the bag, his head goes one direction, his body goes another direction. End of house sparrow. Only good house sparrow is a dead one. Not “shooed” or “scared” away. I use aggressive lethal action against them. I have too many bluebirds and tree swallows that depend on my actions to equalize the field.

  19. Betty says:

    If you are putting up a blue bird or other boxes up . I feel it’s the person’s responsibility to monitor all of the boxes.
    I use the Van Ert Sparrow trap for years. It works great.
    But you have to watch the complete time it’s up.
    I put it up when I’ve seen them go into the box .
    Use a small mesh laundry bag to catch the bird and again to make sure it’s a Sparrow .
    I’ve seen too many song birds killed no matter how many boxes are up . Or where they are

  20. I currently have 2 bluebird boxes up and have seen bluebirds going in and out of both. I too use the Van Ert Sparrow traps with good success. Unlike previous years, the bluebirds are not attentive to the boxes and not protective when I approach. One box has 5 white eggs and the other has 4 light blue eggs. I know the eggs have been there for at least 8 days. (possibly a week longer). I will remove them in another week if not hatched. If the eggs are not viable – would this be a reason for the inattentiveness and absence of the parents.

    • Holly Faulkner, Project Assistant says:

      Hi Kristin, Whenever you suspect a nest is abandoned, we recommend waiting at least 4 weeks from the last time you saw the adults. Birds can sometimes delay incubation and can also be sneaky about their incubation, and so it’s good to let a full incubation period pass plus a week or two to account for this. If after that period the eggs remain unhatched, it’s safe to consider the nest abandoned and you can clean the box out if you wish.

  21. Jenny Ferguson says:

    I also have the Van ERT trap and have killed 13 house sparrows. I could only do this after seeing a house sparrow kill a beautiful male Bluebird.
    Now we have our second successful nesting of Baby Bluebird. You do have to watch the trap closely.
    Ok this is another issue I have.
    Blue birds laid three eggs in the box. I found the eggs on the ground cracked. Then the tree swallows took over the nest. They laid 5 white eggs. The blue birds came back an sat on the eggs until they hatched and are now feeding the babies. Has anyone had this happen. Or heard of bluebirds raising tree swallow babies?

    • Holly Faulkner, Project Assistant says:

      Hi Jenny, bluebirds and Tree Swallows do occasionally have mixed nests – we’ve had reports of nests with eggs from both birds, and some eggs from one species hatched by another. Usually, not all eggs/nestlings successfully fledge, but it’s possible. Additionally, the breeding instinct is often so strong that birds have been known to feed young of other species if they hear them calling. We’d be curious to know how your nest turns out! Please consider reporting the nest to your account on NestWatch, and send us an email with any additional questions: nestwatch@cornell.edu.

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Cornell Lab of Ornithology

Cornell Lab of Ornithology