Standing in a high-grade swamp at the height of the migration, you might be surrounded by hundreds of Soras, but you might leave without encountering a single one. As the Soras move between their breeding grounds in the north-central United States and Canada to their wintering grounds along the southern coasts, Mexico and beyond, they cross almost the whole continent. But because they hide in the reeds of wetlands to survive, Soras are rarely spotted.
Patuxent River Park Naturalist Greg Kearns in Maryland has seen his fair share of Soras and more. Over the past 35 years, part of their effort called Project Sora, he and his team have tagged over 6,000 of these elusive birds at Patuxent’s swamps and wild rice fields. “I think their secretive nature is what protects them and intrigues me,” Kearns says. “Little was known about their migration routes, chronology, and habitat use.” But now scientists like Kearns are uncovering the secrets of these birds, including their fantastic migrations.
Soras are long-distance migrants, but at first glance they hardly seem like one. Tough and stocky-winged, Soras belong to the rail family, a group of marsh birds that largely prefer walking to flying. When they fly away, Soras beats with legs dangling in an awkward, laborious motion that lasts only a short distance. But that changes during the migration seasons, when the Soras head to distant destinations and return. Some even travel to South America, as far as Ecuador or Peru, the longest migration of any North American railroad.
The Patuxent River Park acts as a pit stop for Soras on their travels, though a few winter there. Kearns uses recorded Sora calls to lure the birds into walk-in traps, then he attaches tiny radio trackers to their backs. By using the Motus Wildlife Tracking System, it retrieves data on where these birds are going and how fast they are getting there. This spring, for example, he laid out bird routes north of Patuxent to breeding grounds in the Great Lakes region. One of the most notable migrations recorded by Project Sora saw a bird fly nonstop from Maryland to the Bahamas in less than 20 hours. Another one, which the researchers named Pea, went from Patuxent River Park to Pea Island National Wildlife Refuge in North Carolina in less than 5 hours, a time that would have beaten many motorists driving between the two locations.
In addition, the migrating Soras are constantly fidgeting. Hawks, on the other hand, glide to save energy, and many small birds such as sparrows and finches break their flaps with short bobs in the air (called leaping flight). To quantify what a Sora’s flapping flight really means, Kearns took slow-motion video of one of his migratory journeys. Counting the number of beats it made in 10 seconds and multiplying that number over the bird’s nine-hour journey to North Carolina, he determined that the bird beat about 285,000 times to get there. to arrive. To reach the Bahamas, Kearns estimates that a Sora would take something like 600,000 flaps – or more, if it continues south through the Caribbean. “It’s mind-boggling,” he said.
So how does a ground-loving stilt-walker accomplish these aerial feats? On the one hand, they get a little help. When planning their migrations, the Soras seem to take weather conditions into account, says Auriel Fournier, assistant researcher at the Illinois Natural History Survey. During fall migration in Missouri, she saw masses of them arriving in an area just after a cold front. “After a front like that, there are often fairly steady winds that follow,” she says. “In many cases they jump on these winds after and after the south ones.” Using this strategy, the Soras increase their speed from around 30 to 35 miles per hour unassisted to 45 miles per hour on average, to – in exceptionally strong winds – over 75 miles per hour, according to Kearns’ observations.
But riding the wind is a double-edged sword – on the other hand, Soras is at his mercy, vulnerable to a strong gust from the wrong direction. Some, Kearns speculates, probably die above the ocean. But in extreme cases, deviated Soras have crossed the Atlantic, ending up in the the Canary Islands off North West Africa, the United Kingdom, the Azores, Portugaland even Norway.
To fuel their impressive flurries of migration, the Soras need plenty of time to refuel throughout their journey. Migratory warblers typically rest for a few days at a time, but Fournier says Soras can rest at one site for more than a month, where they grow in size by eating lots of carbohydrates. They change their diet from protein-rich invertebrates to seeds of knotweed, sedges, grasses, or wild rice. “They do a little couch potato routine out there in the swamp,” Kearns says. Soras are steadily gaining mass, and as the start approaches, they gain weight even faster. Birds range from 50 to 60 grams to 80 or 90 grams, Kearns says. Then, with their accumulated fat, the Soras begin to set off with the right winds and clear skies about an hour after sunset.
Doing such an extreme migration takes a toll on the population of Soras, and the birds a large clutch size of 10–12 eggs helps replenish their numbers. But other threats remain: In the past, hunting decimated the Sora. Now, with reduced hunting, climate change and human development causing habitat destruction that complicates Soras’ travels. In Illinois, where Fournier works, more than 80% of the state’s wetlands have already been lost, and it’s a similar story in other states. “It makes life more difficult for them during migration, which can already be a risky time of year,” says Fournier.
But when they land in high-quality habitat, like the wild rice ecosystem at Patuxent River Park, year after year, it’s a testament to the importance of the marsh, Kearns says. These are the places that will allow Soras to continue successfully navigating their death-defying migrations in the future. “That’s really the takeaway,” Kearns said. “We need to protect these wetlands.