Migrating birds seen on US radar

by Matthew Cobb

The US National Weather Service Weather Forecast Office (you could work on the title, folks!) reports that on Friday evening, shortly after sunset, their radar picked up some unusual signals in Wisconsin, near Milwaukee (insert beer joke here). Although some of these blobs may have been snow flurries, the Weather Service suggests that these are more likely to have been migrating birds. The site adds:

The loop below shows the local radar image from 4:53 pm through 5:41 pm. Notice, the strong returns that appear at 5:02 pm and how they spread out and diminish with time.

Radar loop

YouTube has this rather cool video showing

“nocturnal migrating birds, bats, and insects in the continental U.S. from sunset to sunrise Oct. 1, 2008. The blocky green, yellow, and red patterns, especially visible on the east coast, represent precipitation; but within an hour after sunset, radar picks up biological activity, as seen in the widening blue and green circles spreading from the east across the country. The birds, bats, and insects take off, fly past, and get sampled by the radar beam. Note, the black areas on the map do not represent places without birds, necessarily, but rather places where radar does not sample.”

If you want to understand the physics of it all, read this.

h/t @JacquelynGill on Twitter, who also tweeted: “A mass migration of birds is not unusual, as yesterday saw the cessation of southern winds that had made migration conditions unfavorable.”




  1. Posted November 24, 2012 at 10:33 am | Permalink

    Seems to me that this is ripe to turn into a perfect tool for birders. How cool would it be for the USNWSWFO to start making bird forecasts as well as weather forecasts!


    • SnowyOwl
      Posted November 24, 2012 at 5:46 pm | Permalink

      Ah yes grasshopper, this is happening —
      1. eBird.org started adding actual movements as seen on NEXRAD to known, decades-old, calendars of migranting species to better give a heads-up to birders ‘upstream’. Here’s an example from last Spring:
      2.Bill Evans at oldbird.org actually invented a two-part scheme for capturing and then automating, via software, the identification of night flight calls, thus we now use digital-and-human eyes and ears to look into the night for what I call ‘organic meteorology’ to not only ID but get a count. There is a listserv where this stuff is discussed:
      3. US Fish and Wildlife Service sponsored a video conference inviting those of us interested in the latest NEXRAD analysis to view and participate. Going a bit beyond just the mushrooming effect, aerecologists utilize the other radar components to measure speed, direction, and even numbers of biota taking flight. As I’ve said elsewhere in these comments, I work with diurnal raptor migration and now add NEXRAD to the numbers seen from ground observation points to better complete the picture. The bottom of the two videos on this page is that conference call:

      • Posted November 25, 2012 at 7:41 am | Permalink

        Shoulda known — thanks for the links.

        Something suggest to me that the same radar techniques should also show bat colonies and locust swarms and all the rest…talk about serendipity!



        • SnowyOwl
          Posted November 29, 2012 at 3:14 pm | Permalink

          Yes. Somewhere on a disk, from several years ago, I have a daylight flight of Green Darners (Anax junius) in a sine curve over the entire state of New Jersey. If there is a critical mass of an organism, it will show up on NEXRAD!

  2. Posted November 24, 2012 at 11:35 am | Permalink

    I grew up in that Wisconsin area. Could this really be migration in late November? Migrants would have left a long time ago, unless global warming has really messed things up. The “North American” warblers are already here with us in South America now. Maybe this is mass roosting movement of non-migratory birds like starlings and blackbirds and Canada geese.

    • Rick
      Posted November 24, 2012 at 11:56 am | Permalink

      I live in central Indiana and migrating flocks of Sandhill Cranes passed over my house all day.

      • jesse
        Posted November 24, 2012 at 2:19 pm | Permalink

        Initially, I wondered if it was Sandhill Cranes, too! But I am pretty sure they migrate only during daylight hours. At least that is always when I’ve seen them migrating over the Chicago area.

        I did see about 500 Sandhills just west of Madison, Wisconsin, two weeks ago, so some of them might be those you saw in Indiana…it’s nice to think some of us are linked by migrating birds!

        I checked some literature online and all sources verify they roost at night on the ground, in marshes.

        BTW, for anyone wishing to get a happy recharge of the spirit there are some great youtube videos of Sandhills on the Platte River in Nebraska : )

        • SnowyOwl
          Posted November 24, 2012 at 5:12 pm | Permalink

          I am interesting in diurnal migrants… and they are detected on NEXRAD! The trick is, are there enough of them in a concentration that they can be detected?! For your cranes, there are thousands of them for sure, but do they lift-off in large enough numbers? Are there radar stations close enough to the concentrations of birds taking flight to be picked up?
          For hawks in the Northeast, a midday migrant, it is the huge numbers of Broad-winged Hawks moving in a relatively brief window in April and September that can be ‘seen’ on radar. I capture these and compare the radar images to numbers being seen (or not) by hawkwatches, often with professional observers on the ground.
          Here’s a YouTube link to the first of four animations, tracking tens of thousands of Broadwings, with other “hawk” species mixed in, across upstate NY one day last April:

          • SnowyOwl
            Posted November 24, 2012 at 5:14 pm | Permalink

            I forgot… click on the YouTube logo in the lower right corner to read my description and then link to each of the other three videos to follow the hawks along the south shore of Lake Ontario.

      • Posted November 25, 2012 at 6:16 am | Permalink

        Yes, could be Sandhill Cranes….

    • jesse
      Posted November 24, 2012 at 1:29 pm | Permalink

      If it were birds on the radar, then I would agree with your belief as to the species. Warblers are long gone.

      The extreme weather change might have pushed them; it was a balmy 60F on Thursday in southern Wisconsin, then 20F on Friday morning with wicked winds out of the north.

    • SnowyOwl
      Posted November 24, 2012 at 5:00 pm | Permalink

      First, in the Northeast, night flight starts showing on NEXRAD as early as late July (that is, large enough numbers to light up the radar!). At this time of the year it still continues with juncos, tree sparrows, and finches of many species moving in large enough numbers to show up… just think about other species that arrive late — as Winter kicks in — and you’ll add to my short list.
      BTW, huge movements of migrating blackbirds like Red-winged Blackbirds and Common Grackle are detected both by birders and by radar in early November (again, in eastern North America).

      • Posted November 25, 2012 at 6:19 am | Permalink

        Nonmigratory grackles and blackbirds and starlings (and Canada Geese) are much more common than Sandhill Cranes. Cold weather might push these a bit farther south.

  3. Les Kaufman
    Posted November 24, 2012 at 12:16 pm | Permalink

    Tom Kunz of Boston University formalized the study of aerial biological activity as aerecology, with many advances in image analysis and processing. His students are carrying on with this work.

  4. teacupoftheapocalypse
    Posted November 24, 2012 at 1:16 pm | Permalink

    Radar has also been used to solve mysteries regarding the migratory patterns of butterflies – much more difficult to track than birds, by technology-free means. http://www.bbc.co.uk/nature/19991550

  5. MadScientist
    Posted November 24, 2012 at 1:26 pm | Permalink

    I just can’t see it.

    • SnowyOwl
      Posted November 24, 2012 at 5:20 pm | Permalink

      Dear Mad:
      Try this one with a soundtrack…

  6. utah
    Posted November 24, 2012 at 4:16 pm | Permalink

    I just read this book ( http://www.amazon.com/Angry-Letter-God-Manifesto/dp/1481004832/ref=sr_1_2?s=books&ie=UTF8&qid=1353796429&sr=1-2 )and thought that you might find it quite hilarious especially the part with a suggestion that God would be arrested if he ever decide to come back 🙂
    Please read it! 🙂

  7. JohnnieCanuck
    Posted November 24, 2012 at 5:27 pm | Permalink

    Some of the earliest radars to pick up migratory birds in North America were the Pinetree Line sites. I remember visiting the one in Beausejour, Manitoba and being told of the phenomenon.

    We were also told the mandatory tale of the military paranoia it caused before the cause was eventually identified.

  8. Rob Bate
    Posted November 24, 2012 at 5:34 pm | Permalink

    Birders have been using the weather radar for a few years now to show generalized night time bird migration. Coupled with wind maps and weather predictions, especially rain predictions, good “fall-out” days can be reasonably well forecast making finding birds much easier than in years past.

    Some people are able to track birds with microphone pickups to tell how many birds are passing over a particular spot. Good “birders” can even pick out particular species and tell who is flying that night.

  9. Pray Hard
    Posted November 24, 2012 at 8:27 pm | Permalink

    Wow, makes me remember migrations when I was a kid in the country southwest of Fort Worth. The Canadian geese would come and eat the green oat sprouts in the large field north of our farm. Imagine being a kid on very cold, clear, moonlit nights with formations of geese flying across the moon. Life will never be better than those moments.

  10. Posted November 25, 2012 at 7:12 pm | Permalink

    Reblogged this on Sarvodaya.

  11. Ken
    Posted November 25, 2012 at 9:47 pm | Permalink

    A recent paper http://journals.ametsoc.org/doi/abs/10.1175/BAMS-D-11-00099.1

    Also see http://soar.ou.edu/

  12. Posted November 25, 2012 at 9:49 pm | Permalink

    I was in Milwaukee on Friday, and there was intermittent snow. There were no reports of migrating birds in the local media that I am aware of. It would be a bit late for most migrants in SE Wisconsin (where I live). I would lean toward snow as the explanation.

    • SnowyOwl
      Posted November 29, 2012 at 3:23 pm | Permalink

      That is a good beginner’s question.

      First, biota shows up on NEXRAD… has for several decades now.

      The earliest work in North America was by Sid Gauthreaux at LSU showing Spring and Fall movements of nocturnal songbirds over the Gulf of Mexico (one of his early journal papers is dated 1970). Next, you need to do some work: you need to learn what inorganic and organic stuff looks like on radar. That is, birds v. weather.

      And, “reports of migrating birds” doesn’t make the local news!? As this stuff happens at night and is not exactly newsworthy.

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