The Best Tools for Forecasting Bird Movements and Migrations

If birders could have a superpower (specifically for birding), I bet most would wish to see into the future. We’re always trying to figure out the best places and times to bird. Which day is that big migration going to make landfall? Will the birds be hanging out in the woods or at the lake? Should I call out of work sick on Wednesday or Thursday? It’s important foresight. I don’t know anyone who’s gone so far to try a fortune teller, but I’m not saying it’s a bad idea, either.

Or maybe, birders can just use the internet, which now contains a bounty of sources to help them figure out where they need to be when the birds coast into town. Here are the ones I’ve found to be the most useful.

eBird. Back in prehistoric birding times, you needed to know the right people to get precise local histories, or work to write them yourself. Forecasts were based on seasonal arrival dates, built up and honed over years of observation—almanac-style. Birders in Washington D.C. knew to start looking for Yellow Warblers around the third week in April, say, because that’s when Yellow Warblers always show up.

But now, eBird makes it a whole lot easier. Just a few clicks around the website's “Explore Data” tab can reveal all kinds of information about when to expect certain species. Clicking on the “Arrivals and Departures” link from there will give you listings for every reported species, sortable by state, county, hotspot, observer . . . you name it. I’ve found that the species-specific graphs found through the “Bar Charts” selection on same page are equally useful. Clicking from there on a particular species will also get you a lovely little line graph that marks when a bird arrives, peaks, and moves out. (Turns out the third week in April was a pretty strong bet for Yellow Warblers in D.C.)

BirdCast. While eBird’s online features are great for showing you annual patterns, they don’t let you know exactly how well this year’s migration is panning out. For that level of analysis, BirdCast from the Cornell Lab of Ornithology is a one-stop shop. BirdCast uses weather reports, radar, machine learning, and a “completely automated pipeline of algorithms” (whatever that means) to produce region-specific forecasts of bird movements a week in advance.

Unlocking the goods is easy. Simply go to your region’s BirdCast to scope out dozens of migratory species and their arrival dates, which ones are peaking, and which ones will be departing from your area in the coming weeks. The forecasts also reveal how noticeable the migration will be, which in turn, tells you how easy-to-find the birds will be. Even better, BirdCast lets you know the length of the migration window for each species. Each region is fairy large, but the site does a solid job of explaining how the weather will affect migration on a more local level. Honestly, with BirdCast, all you really need to do is remember to bring your binoculars.

Winter Finch Forecast. Ontario ornithologist Ron Pittaway is birding’s Nostradamus—except that Pittaway’s predictions actually come true. He focuses his expert skills on passerines that journey between the northern boreal forests and the Eastern United States: Red and White-winged Crossbills, Evening and Pine Grosbeaks, Common Redpolls, and other species that most American birders rarely see outside of the Rocky Mountains. Some winters, though, these species can be found far south of their typical range. Pittaway knows why and when.

It’s simple, really: Birds will travel epic distances to find food. To make his highly educated guesses, Pittaway studies the chow these birds need to survive the winter —spruce cones, mountain-ash berries, and others—and determines whether there will be a big winter crop or not. A rich crop means that the birds won’t need to go far to eat, but a down year means they may fly well south, into the waiting binoculars of U.S. birders. Pittaway puts his findings online, and this winter’s forecast reports a bumper crop of food across eastern Canada. So most of us down here will just have to wait until next year for any irruptions.  

Weather Radar. If you want to take the next step and craft your own predictions, think about watching radar. As large masses of birds (and bats and insects) take off into the air to begin the evening’s migratory movement, they interact with the pulses of electromagnetic energy shot out by weather stations to identify clouds and rain. Those masses of animals can then be seen on maps as a growing circular blob, or, more eloquently, a “bloom,” around the radar base.

The keen birder can then “read” the bloom, interpreting the patterns, speed, direction, and other data to get a sense of how many migrants might be on their way that night. Combine that information with larger weather patterns (for example, any fronts in the area that may ground large flights) or geographic features (migrating birds almost always stop near the coast) and you can get an idea of how productive the birding might be the next morning. The National Weather Service has some great nightly images to get you started; but you can also follow these active forecasters on Bird Twitter for plenty of tip offs when good migrations are getting underway.