By Rob Thorn
The mud made a crunching sound underfoot, with some parts of it frozen for the first few inches. It was a freezing December day as we walked around the mudflats at the upper end of Hoover Reservoir, mostly looking for waterfowl and gulls. Some of the shallow pools had iced over, but the main part of the reservoir was open, and had lots of birds. What we weren’t expecting were shorebirds. Sure, a few Killdeer wasn’t surprising; these hardy plovers can survive well away from the shore, even in cold areas like Ohio. But we also had a few yellowlegs and a flock of Dunlin. I might expect these in Chesapeake Bay, but central Ohio in winter?
Turns out, this wasn’t a mirage. Several species of shorebirds have started to hang out in Ohio in late Fall and early winter…in small numbers, mind you, but they’re still here. Greater Yellowlegs, Wilson’s Snipe, Dunlin, Pectoral Sandpiper, Least Sandpiper – all now have regular records in Ohio in November and December. Like many of our dabbling ducks, they appear to hang around until their wetlands absolutely freeze. This extends a pattern noted almost 2 decades ago, where many migrating shorebirds started to linger in Ohio through October (see https://www.bsbo.org/timing-of-fall-shorebird-migration.html ). Looking at their distribution maps, you can see that many of these birds winter in the southern states and up along both seacoasts to our latitude or even higher. Dunlin winter regularly north to New England and British Columbia (see https://www.allaboutbirds.org/guide/Dunlin/maps-range ). Wintering Greater Yellowlegs reach up to Ohio’s latitude on both coasts (see https://www.allaboutbirds.org/guide/Greater_Yellowlegs/maps-range ). So the cold isn’t much of a deterrent for these birds.
Still, to stay in Ohio in these months must offer some advantages and require some tricks. One obvious advantage is a shorter migration. Why spend all that time and energy migrating south to Mexico if you can short-stop in the Midwest? Another is lack of predators. Until recently, Ohio had no real shorebird predators outside of migrant raptors. After nearly two decades of watching winter shorebirds in Washington State, I can vouch for the fact that Peregrines and Merlin were constant attendants anywhere that had large shorebird flocks. This BirdNote podcast explores this predator-prey relationship: https://www.birdnote.org/podcasts/birdnote-daily/peregrine-shorebird-interaction . Ohio wintering shorebirds are not numerous enough yet to attract the attention of bird-specific predators. Ohio has a few wintering Merlin now, but they seem to focus on urban starlings and doves.
But there is one major disadvantage. How can these birds find food in the cold months? Well, firstly, the months are not so cold anymore. Global warming has made lakes in the Midwest anywhere from 1-3 degrees warmer in the past decades. This allows a number of fairly cold-tolerant insects like midge and mayfly larvae to maintain activity deep into fall and even winter. Midge numbers have been on the increase around northern Ohio already (see https://www.youtube.com/watch?v=IP5II_nAaOY ). There are also a number of exotic invasives, like the spiny water flea (see https://www.youtube.com/watch?v=7yDuwqkTu6Q ), that are active longer into the cold months, offering yet more food options.
So it looks as if two human-caused changes – warming temperatures and invasive food organisms – may help play a role in these species’ decision to linger around Ohio into winter. There’s another human-derived change that probably also plays a role here. We’ve created a lot more shallow wetlands for these birds to stop at. Three decades ago, people mourned about the steep loss of Ohio wetlands. In the intervening decades, however, stronger protection for wetlands and the development of mitigation wetlands have cause an expansion of these habitats. Locally, we now have wetlands in Pickerington Ponds, Slate Run Metro Park, Battelle Darby Metro Park, Taylor Farm Park, and Dawes Arboretum, just to name a few. None of these were here 30 years ago. New foods, new climate, new habitat: It would probably be surprising if we didn’t get more lingering shorebirds. Keep that in the back of your mind when you venture out to the shore this winter.