Expected nocturnal migrants flying through Clallam County on the night of April 25-26, 2023, as shown by BirdCast Migration Dashboard.
Getting to Know BirdCast
May 2023
by Bob Boekelheide
Attention OPAS members! Do you know about BirdCast? Researchers from many different institutions, particularly Cornell University, Colorado State University, and University of Massachusetts Amherst, have developed a phenomenal tool called BirdCast that revolutionizes our awareness and perception of bird migration over the United States. Bookmark it now!
These researchers have combined the nation-wide network of over 140 NEXRAD weather radars with powerful computers and citizen-science eBird observations to produce striking visions of bird movements across the United States. All birders, including those of you who simply watch backyard birds at your feeders, need to bookmark BirdCast and consult it regularly during spring and fall migrations. I guarantee that BirdCast will expand your knowledge and appreciation of birds and bird migration.
When radar first developed before World War II, it soon became obvious that radar picked up more than just flying aircraft, particularly at night. In Britain, the Royal Air Force scrambled planes at night when the radar showed incoming images, but to their surprise they found no aircraft in the area. These “angels,” as they were called, turned out to be flocks of migratory birds, bats, and insects passing by when conditions were best for migration. Modern doppler radar can filter out these spurious images, or, in the case of BirdCast, specifically highlight these images to study bird migration patterns.
Early radar and bird collisions with human structures confirmed that many migratory birds, particularly small songbirds, migrate at night. Subsequent research showed that these birds use star patterns to orient themselves while flying. Birds consequently need relatively clear skies during their long flights. Using this knowledge, Cornell and a host of computer experts sought to predict when and where large migratory flights will take place, and try to track the migratory flights as they occur using doppler radar. BirdCast is the result of their efforts.
BirdCast is not a cellphone app. It is an on-line website instantly available to any computer with web access. Do a search on your browser for https://birdcast.info/, or simply Birdcast, and you will see that there are four tabs across the top on the home page: “About,” “Migration Tools,” “Science-to-action,” and “News.” The heart of BirdCast is Migration Tools, which provides a host of information about recent and upcoming bird migration for specific areas across the United States.
The first tab under Migration Tools is called “Bird Migration Forecast Maps.” These maps provide predictions about the intensity of bird migration over the next three nights for the continental U.S. The predictions combine weather variables such as precipitation and cloud cover along with 23 years of bird movements recorded by NEXRAD radar, to produce heat maps that literally glow with bright colors in areas expected to have high bird migration.
Figure 1. Bird migration forecast for the night of April 28, 2023, showing the intensity of bird migration across the continental United States. The bright glow in Texas shows high bird migration movements, whereas the dimmer glow on the West Coast, including Washington, indicates medium movements. The dark area through the Rocky Mountains suggests few birds will migrate through that region, although, as Birdcast admits, mountainous terrain may block radar and not provide a complete picture of real conditions.
The second tab under Migration Tools is called “Live Bird Migration Maps,” which is truly amazing. These maps use real-time data from weather radars across the U.S. to show where birds are actually migrating during a given night. Once you click the start arrow, the maps glow in areas where birds are flying, as well as show the elapsed time and sunset and sunrise. It is fascinating to watch the movements of birds in areas of higher migration rates, as indicated by arrows from weather radar sites. Once again, this is real-time data, as it’s happening. Can it get any better than this? (Maybe so – see below).
Figure 2. Live bird migration map stopped at 3:50 am ET for the night of April 26, 2023. Once again, areas of higher bird migration rates glow brightly, whereas dark areas indicate low migration rates. The map shows high bird migration especially in Texas, with medium to high migration through Florida to the Great Plains, and along the West Coast, including Washington. The Rocky Mountains and New England are dark, indicating little migration.
The third tab under Migration Tools is called Local Bird Migration Alerts. At this tab, you enter the name of a town or city, such as Sequim, WA, and receive predictions about the intensity of expected bird migration at that location over the next three nights. The given prediction is either low, medium, or high, depending on the expected density of migratory birds each night.
Predictions are surprisingly specific, so on any given night the prediction for Sequim might be quite different than the prediction for Port Townsend, Neah Bay, or Seattle. Lately, it has not been unusual for the expected spring migration through Sequim and Port Angeles to be lower compared with Seattle and Port Townsend, making me wonder whether the Olympic Mountains create a “migration shadow” for Sequim and Port Angeles during spring migration, similar to its renowned rain shadow. It makes sense that small birds flying north in spring likely go around the Olympic Mountains rather than fly over them.
Local Bird Migration Alerts also gives you the option to receive an email “alert” when your chosen location expects high migration rates. There is an important conservation message to this, as well. A high migration alert stresses the importance to turn off bright outdoor lights when many birds are migrating, to prevent disorienting them and reducing the likelihood of collisions with buildings and other objects.
The fourth and last tab under Migration Tools is one of the best, called “Migration Dashboard.” This incredible tab links the migration data from BirdCast with millions of historical data points from eBird for a chosen county or state. It determines the expected species that were likely migrating on a given night, how many birds migrated during the night, what time they were flying, and what direction and altitude they used. It also shows graphs of the cumulative number of birds through the migration season, comparing them to historical data. For the last week in April, for example, it used eBird bar graphs to show that expected species ranged from Sandhill Cranes and Semipalmated Plovers to Warbling Vireos and Wilson’s Warblers.
Figure 3. Migration Dashboard data for Clallam County during the night of April 25-26, 2023, as shown on BirdCast Migration Dashboard.
Figure 4. Expected nocturnal migrants flying through Clallam County on the night of April 25-26, 2023, as shown by BirdCast Migration Dashboard.
BirdCast gets my vote as one of the best uses of powerful computers and huge data sets ever devised.
As far as recent bird sightings, spring 2023 seems to be a repeat of spring 2022, starting out with several weeks of cold temperatures and rain, then spikes in bird migration after conditions improve. Bird migration through March and April this year crawled along until the last week in April, when warmer temperatures and clear nights finally showed up on the north Olympic Peninsula. The flood gates opened! Soon the neotropical migrants will arrive – flycatchers, Black-headed Grosbeaks, Western Tanagers, flashy warblers, swifts, nighthawks, and, one of the greatest singers of all, Swainson’s Thrushes.
As I frequently say this time of year, you must get out now to hear bird songs. The nesting season for many birds peaks in May and June, but it’s over very quickly. The bird song switch gets turned off in the first half of July. This means that you have just over two months from right now to hear one of the most incredible natural events of your lifetime. Every singing bird is a priceless connection to nature.
Now is the time to prepare yourself for Birdathon. What is the best way to get ready? Go birding! We need an army of birders to hit their backyards and birding hotspots on May 13, to adequately survey the birds of Clallam County. See the article about Birdathon in the Events Calendar for more details.