Science

The Real Reason Behind This Year’s Bizarre Spoonbill Sightings

The exotic pink birds appearing up north are part of a larger wading bird wave, driven by this summer's breeding boom on the Gulf Coast.

On August 26th, the rare-bird alert went out. A Roseate Spoonbill, the first on record for Minnesota, was discovered just 30 minutes outside of the Twin Cities—nearly a thousand miles outside the species’ usual range in the Southeast. It followed on the heels of a Wood Stork in New Hampshire and a Great White Heron in Ohio, both thousands of miles away from their Florida homes as well. Between the three of them, the wayfarers racked up enough mileage to fly from the White House to Buckingham Palace.

Yup, it was an exciting August—and the excitement isn’t over yet. Spoonbills have popped up in Saint-Martin, Quebec, Sebec, Maine, and as recently as this week, Stratford, Connecticut (perhaps the same individual seen in Maine).

The sightings are sensational, but they aren’t exactly random: They represent an ongoing pattern in North American breeding cycles. Wading birds such as Wood Storks, Reddish Egrets, and spoonbills are occurring farther and wider than they have in years following an exceptional breeding season, thanks to the strongest rains the Gulf Coast has seen in 80-some-odd years. It’s a phenomenon that mirrors what we see in Snowy Owls and winter finches, when a summer-breeding boom is followed by unexpected records outside the species’ ranges.

While each vagrancy event is fascinating and exciting in its own right, one has to wonder about the broader impulses. What could possibly drive these individuals to fly so far in the “wrong” direction?

Birders and ornithologists have long speculated about what makes vagrants ticks. Some believe the birds get lost due to defective navigation systems. Others look to the weather, arguing that rarities are swept up by storm fronts and transported to parts unknown. Others still contend that some fraction of all bird populations have an inherent tendency to disperse far—in other words, that vagrancy is normal for any species. If certain individuals are born with a genetic predisposition for exploration, known as neophilia, then the pattern would be exaggerated in breeding-boom years.

These explanations are all hypothetical; it’s tough to put them to the test without a large sample of vagrants. We may never understand some truly mind-bending rarities, like this year’s Eurasian Skylark in Quebec or the Tahiti Petrel offshore from Hatteras (unless we somehow have the foresight to place GPS trackers on individuals yet-to-be famous).

That said, we can still take a step back and consider the bigger picture. Take spoonbills, which have so far been spotted in Minnesota, Iowa, Ohio, Maine, and Connecticut this year. While exciting, these out-of-character movements aren't really novel. Dr. Richard Veit, a vagrancy expert and ecologist at the College of Staten Island (City University of New York), recalls many other exceptional sightings from the past, like the “famous Roseate Spoonbill on Staten Island in 1992, as well as a probable second bird on Block Island, Rhode Island the same summer.” Rather than attributing them to unusual weather or behavior, Veit points to a “combination of large production of young, coupled with depletion of resources" that send birds seeking food in farflung places.

Still, that doesn’t account for the distance these birds have travelled. Can a spoonbill coast a thousand miles outside of its range without the asterisk of inclement weather? Sure it can. Roseate Spoonbills breed along vast stretches of coastline along the Gulf of Mexico, Mexico’s Pacific Coast, and around the Caribbean, not to mention their year-round residence across South America. A regular flight from Florida to Panama could span up to 3,500 miles of circum-Gulf migration; A journey of 1,500 miles between Florida and Maine, then, should be well within their abilities. And while most spoonbills probably have no reason to venture so far north, young and inexperienced birds—which made up most of the sightings this year—might just make the trek.

In the context of the summer of 2018, this all makes sense. The wading bird blitz on the Gulf means more individuals are competing for prey and space. This ups the chances that some individuals would opt to explore far and wide to find less-crowded habitats with ample food. “Maybe only 1 percent of birds go as far as Pennsylvania,” Veit says. “But if there are hundreds of birds dispersing, then 1 percent is a substantial number.”

Especially for daytime migrants like spoonbills, herons, ibises, and Wood Storks, these explorations may be par for the course. Indeed, ever since birders have been tracking vagrancies, the number of far-north sightings has ebbed episodically. In fact, it’s phenomena like these that help species expand their ranges or even, given enough time, establish colonies that split into new species. And while the exact details of each vagrant’s journey may be a mystery, we can temper our expectations that rare birds always come with a dramatic backstory. Sometimes, weather and behavior notwithstanding, a vagrant may just be a loner looking for a place to itself.

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