Intense Migration Coming Thurs Night, Sep 10-11

Swainson’s thrush, western Pennsylvania, October 2012 (photo by Steve Gosser)

9 September 2020

The bird forecast for tomorrow night is GREAT in Pittsburgh. BirdCast and Aeroecolab’s Lights Out Alerts predict that 401.1 million birds will migrate over the continental United States on the night of 10-11 September 2020.

Screenshot from Lights Out Alerts, 9 Sept 2020 at

Migration will be especially intense over western Pennsylvania at 19,000 birds/km (about 12,000 birds/mile!). See the red color on Aeroecolab’s 10 September map below.

PA screenshot from Lights Out Alerts, 9 Sept 2020 at

The migrants may not stop here but if you step outdoors three hours after sunset you will probably hear them. Many will be Swainson’s thrushes, shown above, traveling at night.

“Our” Swainson’s thrushes (Catharus ustulatus) nest in Canada and spend the winter in Central and South America. Though numerous on their breeding grounds we only see them on migration, typically for three weeks in September beginning September 9.

Range map of Swainson’s thrush (image from Wikimedia Commons)

As they migrate they make contact calls that sound like spring peepers overhead in the dark.

Although Swainson’s Thrush is still considered one of the most common birds of northern spruce-fir forests, populations are declining even where abundant, particularly in Alaska and the Northeast.

Swainson’s thrush, Birds of the World

Take some time to step outdoors on Thursday night or very early Friday morning to listen for Swainson’s thrushes. Because they are in decline, it’s a privilege to hear them.

UPDATE 11 SEPT 2020, 10:30am: Migration was intense last night but this morning dawned gray and overcast. Without sun to warm the insects, birds were not very active at Frick Park at 9am and the light was so poor that I couldn’t identify the most of them. Yesterday was much better. Weather is everything!

p.s. Click here to get BirdCast local migration alerts for your hometown.

(photo by Steve Gosser, range map from Wikimedia Commons, today’s screenshots from Lights Out Alerts)

4 thoughts on “Intense Migration Coming Thurs Night, Sep 10-11

    1. Jennifer, I have noticed that there’s a cricket that makes that noise. I got excited when I heard it at home last month but no, not a thrush.

  1. Hi Kate. Does the City of Pittsburgh pay attention to this at all? Not sure how/if BirdSafe and the City communicate. I would think that, with many people working from home, a lot of buildings should be dark downtown. But I don’t think that’s the case.

    1. Melissa, I don’t know if/when/who shuts off the lights. BirdSafe Pittsburgh would know. Contact them to find out.

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