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Eastern Bluebirds Nesting

4-22-16  bluebirds nesting 239

Eastern bluebirds are preparing for the first of the two or three broods they will raise this summer.  Contrary to what those of us who clean out our bluebird boxes have been led to believe, Cornell Lab of Ornithology states that experiments show preferences for nesting boxes containing old nests. In a paired experimental design bluebirds chose boxes containing old nests in 38 of 41 cases in which boxes with old nests were paired with empty ones.  Scientists conjecture that this may be because the old nests often contain wasp larvae, an easy source of food for the bluebirds.

Females build their nest over several days.  Grasses and pine needles are gathered from the ground and delivered to the nest box.  Fine grasses, horse hair and turkey feathers often provide the soft, innermost lining of the nest.  While the male enters the box during the nest-building process, perhaps to inspect, he does not actively collect material or participate in the building of the nest. Once the 3 – 7 eggs are laid, the female spends the next two weeks or so incubating them.  She then broods the young for about a week, and both parents provide them with food for up to three weeks after the young have fledged. (Thanks to Jeannie Killam and Terry Ross for photo op.)

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16 responses

  1. Cheron barton


    Sent from my iPhone


    April 22, 2016 at 9:02 am

  2. Dana

    Hi – I would love to know more about the Cornell study that found that eastern bluebirds prefer boxes with older nests. I can’t find that study – can anyone provide that info? Thanks!

    April 22, 2016 at 9:12 am

    • Here’s the info: Davis, W. H., P. J. Kalisz, and R. J. Wells. 1994. Eastern bluebirds prefer boxes containing old nests. J. Field Ornithol. 65:250-253.

      April 22, 2016 at 9:52 am

  3. Pat

    What an exquisite photo! I wonder if the metal covering on the roof is to make it more slippery for would-be predators? (Or maybe there was just a hole in the roof!)

    April 22, 2016 at 10:20 am

  4. Joan Oppenheimer

    Fabulous photo – among many many others.

    April 22, 2016 at 11:20 am

  5. Hmmm, to clean out or not to clean out… that is the question. I used to not clean out, thinking it was better to just leave it for the birds to take care of. Then I started feeling bad about having non-cleaned nest boxes, like it was somehow bad for the birds, so resumed cleaning out. Now I’m confused.

    April 22, 2016 at 12:11 pm

  6. mariagianferrari

    I love bluebirds. I didn’t see them very often when I used to live in MA, but now that I live in northern VA I see them everywhere–love them!!

    April 22, 2016 at 12:31 pm

  7. Grace Lambert

    Does the male feed the female while she incubates the eggs?

    April 22, 2016 at 4:19 pm

    • Yes, he does, and she leaves the nest for short periods to feed, as well. I’ve read that the frequency with which he brings her food effects the length of incubation.

      April 23, 2016 at 8:02 am

  8. The wasp larvae referenced in Davis’ study don’t provide food for bluebirds. They’re far too tiny, and bluebirds don’t forage inside best boxes. Rather, the presence of these parasitic wasps in used bluebird nests may favor the bluebirds because the wasps parasitize bluebird blowfly larvae, which suck the blood of nestlings and weaken them. The infestations of blowflies can run into the hundreds. I clean all boxes between each brood, changing the nests in parasitized boxes when young birds are a week old.

    April 23, 2016 at 6:40 am

    • Cindy

      One of the reasons this site is so awesome – besides MH, of course, are the folks reading and commenting and adding to, in their own way are often just as good! Thank you Julie!

      April 25, 2016 at 8:35 am

  9. Hi Mary, I’ve been trying to comment here; forgive me if you have comment moderation on. Totally thrilled with what may be the perfect nest-building photo of bluebirds! I wanted to add that the wasps that may be present in used bluebird nests are nearly microscopic, and as such are not a food source for bluebirds. Rather, the wasps parasitize the bluebird blowfly, Protocalliphora sialia, that in turn suck the blood of young bluebirds. If present in used nests, the wasps will parasitize the blowflies and reduce the infestation. That may be the ultimate reason that bluebirds prefer houses with old nests in them, as speculated by Davis in his 1994 study.

    April 23, 2016 at 7:27 am

    • Thank you so much, Julie. The source I used didn’t state why the bluebirds would choose to have the wasps present, so I assumed, erroneously, that they were a source of food. Delighted to know the real reason for their preference. Thanks so much for providing this information!

      April 23, 2016 at 7:54 am

  10. Will Simpson

    Was the study limited to only old bluebird nests? What if the box had a house wren nest from the previous year?

    April 25, 2016 at 1:51 pm

    • I honestly don’t know the answer to your questions! Here’s the source: Davis, W. H., P. J. Kalisz, and R. J. Wells. 1994. Eastern bluebirds prefer boxes containing old nests. J. Field Ornithol. 65:250-253.

      April 25, 2016 at 5:26 pm

  11. I do trust all the ideas you’ve introduced in your post. They’re very convincing and will definitely work. Nonetheless, the posts are very brief for beginners. May you please prolong them a bit from subsequent time? Thanks for the post.

    December 18, 2016 at 6:59 pm

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