Bluebird nesting numbers strong despite worrisome winter

Birdhouse monitor shares observations from Wild River State Park in wake of deadly migration last spring.




3 minute read

Originally published by Wild River Audubon:

Eastern bluebird nestlings at Wild River State Park. (Gloria Peterson)

Last spring thousands of bluebirds were lost when they encountered wet, freezing weather while migrating north through the central states. As the monitor of the bluebird trail in Wild River State Park, I wondered how many of “my” bluebirds would return to the park’s nesting boxes.

This is my fifteenth year as the monitor of bluebird boxes in Wild River State Park. I do it for the park and the Bluebird Recovery Program of Minnesota.  I check nineteen pairs of boxes on a weekly basis, looking for nests and counting eggs and nestlings. I clean out the boxes after the nestlings have fledged. Frequently the birds nest a second time. 

The boxes are in pairs spaced about ten feet apart so Tree Swallows can use one box and Eastern Bluebirds can use the other. I had fifteen Tree Swallow nests this year.  I don’t count their eggs and hatchlings for two reasons: they use found feathers in their nests, making it hard to count without reaching in and moving feathers; and I report to the Bluebird Program, not the Tree Swallow Program.

In the spring I was concerned because I didn’t see any eggs during the month of April. In the previous five years all the first eggs of the season were laid in April.  The earliest, in 2020, was laid on April 15th.  This year I first had eggs on May 4th.

At that point I feared the worst. This was a late start. But then eggs started showing up in other nests, and although I didn’t expect to end up with the 102 fledglings of the previous year, I knew this year wouldn’t be a bust.

Bluebirds lay one egg a day and don’t start incubating them until the last one is laid. Then they all hatch the same day.  Eggs hatch about fifteen days after the last one is laid. The hatchlings grow quickly and are ready to fledge at about eighteen days old.

The end of the season was interesting. Usually all of the babies have fledged by the end of July or during the first week in August. This year I found a new clutch of eggs on July 18th and two new clutches on July 25th. One was a third nesting. Very unusual!  The other two were first nests in those locations. Maybe they were second year birds that needed time to find mates and boxes before starting.

Another fear this summer was the hot weather.  Would nestlings become overheated and die in the nest?  No.  A couple of times I found a nest or two with babies that looked slightly lethargic, but they were fine the next time I checked. In my experience the heat does not kill baby birds.  I’ve had more trouble in years when eggs hatch in the early spring, and then we have cold rain. Sometimes newly hatched babies don’t survive that.

When I checked the boxes on August 9th, all three of the late nests had hatchlings in them. I was struck by the fact that in all three nests, the babies were lying with their tails in the center of the nest and their heads going outward.  I’ve seen this many times before, but I never thought about about it beyond the beautiful radial symmetry they produce (Art Teacher here). But then I thought about the heat. Their radial design is good for dealing with the heat. It keeps their vital organs away from each other’s body heat. Cool! (In more ways than one)

Oh, I suppose you want to know the final fledgling count:

  • 2021 – 74
  • 2020 – 102
  • 2019 – 73
  • 2018 – 65
  • 2017 – 67
  • 2016 – 89

This year’s count bettered three of the previous five years’ counts!


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8 responses to “Bluebird nesting numbers strong despite worrisome winter”

  1. Mark Hove Avatar
    Mark Hove

    Informative, personal, delightful

  2. Claire L McCarty Avatar
    Claire L McCarty

    Loved this article. Thanks for your work!

  3. Barb Wetzel Avatar
    Barb Wetzel

    Informative & engaging article. I liked your personal perspective, not just the facts.

  4. Anita Martin Avatar
    Anita Martin

    Do you happen to know what happened to other species this year? I usually have at least 12 varieties who visit my feeders and prairie garden every summer, but I had absolutely 0 during this summer. I live in Afton right next to a nature conservancy. Finally got a few crows in September and a few Blu-Jays are back. There are a few small variety and a mom and baby Pilliated also visited. I really missed the birds!

    1. Peggy Boike Avatar
      Peggy Boike

      I normally have a pair of house wrens nesting in a box in my garden. I love having them because they eat lots of insects. This year a male wren arrived, filled the box with sticks and sang his little heart out for weeks, trying to attract a mate. A female never joined him, and he finally gave up.

      I did not notice fewer birds at my feeder, however.

  5. Pat Meyer Avatar
    Pat Meyer

    Very interesting and informative. I monitor 60 bluebird house at a golf course in Wausau, WI. Last year we had over 150 bluebirds fledge. This year we did not have one bluebird nest at the course. It was quite disappointing.

    1. Peggy Boike Avatar
      Peggy Boike

      Sorry to hear that. Very disappointing, indeed. I have 10 pairs of boxes on a golf course in Lindstrom, MN. Typically around 35 bluebirds fledge. In 2021, there were only 20.

  6. Mark White Avatar
    Mark White

    Your “my” bluebirds have a special survival instinct thanks to you. Doubt any other Minne EABLers had any where near the fledging success in ’21 that you’ve achieved. Really believe those that returned were motivated by love to make it back. Do you affectionately sing “Zippity Doo Daa” to endear them to you ?


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Bluebird nesting numbers strong despite worrisome winter