BirdCast

BirdCast improves birding—and bird safety

By Barb Gorges

            Last year, the folks at Cornell Lab of Ornithology improved and enhanced BirdCast, http://birdcast.info/. You can now get a three-night forecast of bird migration movement for the continental U.S. This not only helps avid birders figure out where to see lots of birds but helps operators of wind turbines know when to shut down and managers of tall buildings and structures when to shut the lights off (birds are attracted to lights and collide), resulting in the fewest bird deaths.

            The forecasts are built on 23 years of data that relates weather trends and other factors to migration timing.

            Songbird migration is predominately at night. Ornithologists discovered that radar, used to detect aircraft during World War II and then adapted for tracking weather events in the 1950s, was also detecting clouds of migrating birds.

            There is a network of 143 radar stations across the country, including the one by the Cheyenne airport. You can explore the data archive online and download maps for free.

            CLO’s Adriaan Doktor sent me an animation of the data collected from the Cheyenne station for May 7, 2018, one of last spring’s largest local waves of migration. He is one of the authors of a paper, “Seasonal abundance and survival of North America’s migratory avifauna,” https://doi.org/10.1038/s41559-018-0666-4, based on radar information.

            At the BirdCast website, you can pull up the animation for the night of May 6-7 and see where the migrating birds were thickest across the country. The brightest white clouds indicate a density of as many as 50,000 birds per kilometer per hour—that’s a rate of 80,500 birds passing over a mile-long line per hour. Our flight was not that bright, maybe 16,000 birds crossing a mile-long line per hour. A strong flight often translates into a lot of birds coming to earth in the morning—very good birdwatching conditions. Although if flying conditions are excellent, some birds fly on.

            I also looked at the night of May 18-19, 2018, the night before last year’s Cheyenne Big Day Bird Count—hardly any activity. The weather was so nasty that Saturday, our bird compiler rescheduled for Sunday, which was not a big improvement. We saw only 113 species.

            Twenty-five years ago, the third Saturday of May could yield 130 to 150 species. Part of the difference is the greater number of expert Audubon birders who helped count back then. Birding expertise seems to go in generational waves.

            But we also know that songbird numbers are down. I read in Scott Weidensaul’s book, “Living on the Wind,” published in 1999, about Sidney Gauthreaux’s 1989 talk at a symposium on neotropical migrants. He used radar records to show that the frequency of spring migrant waves across the Gulf of Mexico was down by 50 percent over 30 years. Radar can’t count individual birds or identify species, but we know destruction or degradation of breeding and wintering habitat has continued as people develop rural areas.

            But I also wonder if, along with plants blooming earlier due to climate change, the peak of spring migration is earlier. A paper by scientists from the University of Helsinki, due to be published in June in the journal Ecological Indicators, shows that 195 species of birds in Europe and Canada are migrating on average a week earlier than 50 years ago, due to climate change.

            Would we have been better off holding last year’s Big Day on either of the previous two Saturdays? I looked at the radar animations for the preceding nights in 2018, and yes, there was a lot more migration activity in our area than on the night before the 19th. Both dates also had better weather.

           As much fun as our Big Day is—a large group of birders of all skill levels combing the Cheyenne area for birds from dawn to dusk (and even in the dark)—and as much effort as is put into it, there has never been a guarantee the Saturday we pick will be the height of spring migration.

           The good news is that in addition to our Big Day, we have half a dozen diehard local birders out nearly every day from the end of April to the end of May adding spring migration information to the eBird.org database. It’s a kind of addiction, rather like fishing, wondering what you’ll see if you cast your eyes up into the trees and out across the prairie.   I recommend that you explore BirdCast.info (and eBird.org) and sign up to join Cheyenne Audubon members for all or part of this year’s Big Day on May 18. See the chapter’s website and/or sign up for the free e-newsletter, https://cheyenneaudubon.wordpress.com/newsletters/.

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