“Moonbird,” they call him. Or sometimes, just “B95” – the number from the band on his leg. Moonbird is the most famous, charismatic member of a group of mid-sized shorebirds called Rufa red knots, whose numbers have plummeted so dramatically in the last several decades that they just became the first bird ever listed under the Endangered Species Act with climate change cited as a “primary threat.”
Rufa red knots are among the avian world’s most extreme long-range fliers (especially in light of their relatively small size). They travel vast distances – some flying more than 18,000 miles – in the course of an annual migration that begins in Tierra del Fuego, Argentina, and extends all the way up to the Canadian Arctic (and back again).
Which brings us to Moonbird’s distinction: Because he is so old – he is at least 21 – he is believed to have flown as many as 400,000 miles in his lifetime. The distance to the moon varies, depending on where it is in its orbit, but the average distance is about 237,000 miles. Thus, Moonbird has not only flown the distance it takes to reach the moon – he also has covered the bulk of the return voyage.
We know Moonbird’s age, said nature writer Phillip Hoose (who has written an eponymous book about him), because he was originally banded in 1995. And even then, he was an adult bird, meaning he was at least 2 years old. Since then, the same bird, with the same tag, is still being spotted, most recently in May 2014 in New Jersey. That would make Moonbird at least 21 years old, a true Methuselah for his species.
As a red knot, “if you can make it past your first year, you’ll live to be 6 or 7,” Hoose said. “The idea of a bird that’s 21, or 22, or even older, is really extraordinary.”
Assuming that Moonbird is still living, there are reasons to wonder whether there will ever be another bird that is his equal. Why? Simply put, his subspecies has been devastated, and climate change will only make matters worse – making extreme survival of the sort that Moonbird has achieved that much more difficult.
“It will become harder for a Rufa red knot to have that kind of longevity,” Hoose said.
According to the Fish and Wildlife Service, there has been a 75 percent decline in numbers of Rufa red knots since the 1980s. One key reason is the birds, during their northward migration, stop off in Delaware Bay in May and dine on the buried eggs of horseshoe crabs – a food source upon which they vitally depend. But those crabs saw their numbers plummet when fishermen realized that if they chopped up horseshoe crabs and threw them in the water, the smell would draw in eels and conch. When numbers of horseshoe crabs crashed, so did numbers of the birds.
“The decline started in the ’90s, and there was a virtual collapse in 2003,” Larry Niles said, a wildlife biologist who studies the red knot in collaboration with the American Littoral Society and the Conserve Wildlife Foundation. “We went from 50,000-60,000 birds down to 20,000, and then hit rock bottom at around 12,000.”
As Niles suggests, the more you learn about the Rufa red knot, the more you also realize how vulnerable it is. Because these birds fly so far, their bodies change dramatically to allow them to complete their journeys. They’ll take on fat and build flight muscles, and then fly 1,500 miles or more at a single stretch, arriving at their destination exhausted and very vulnerable, and overwhelmingly dependent on being able to find easy food – which is what horseshoe crab eggs used to represent.
“We had actually attached small devices that tracked their migrations,” Niles said, “and they made six-day flights without stopping to get to the Delaware Bay. So they would arrive completely bereft of energy, their weight would be sometimes far lower than their fat-free weight, which meant they were burning muscle to get to the Delaware Bay. And the horseshoe crabs were laying eggs in such density that there was no work involved.”
Niles says the “synchrony” involved here – in which the birds managed to arrive at the bay, from thousands of miles away, precisely when the crabs were laying eggs – was “virtually magic.” For a while, anyway. Evolution and adaptation built a pretty good, albeit highly elaborate, survival strategy – until everything changed.
Clearly, for all of these reasons, the Rufa red knot is a pretty amazing bird. Is it the most amazing of them all? That’s subjective and hard to say. The Arctic tern flies farther each year (it’s also a larger bird). And there’s something pretty stunning about the peregrine falcon killing its prey through over 200-mph dives in mid-flight. Still, at minimum, the extremity and Hail Mary accuracy of the Rufa red knot’s long-distance flights have to win some serious respect – and some serious concern for its plight.
The horseshoe crab population collapse, and its after-effects, is the most immediate reason for the Endangered Species Act listing of the Rufa red knot (one of six subspecies of the red knot found around the globe – all of which are struggling, Niles said). But on top of the crash at the Delaware Bay, there are also many other changes along the birds’ vast flyway, and some of those involve climate change.
The birds breed in the Arctic, the region of the world that, more than any other, is being dramatically altered by climate change. Global warming is driving more Arctic storms, said Niles, which can wipe out young chicks. In addition, climate changes in the Arctic are disrupting lemming populations, said Fish and Wildlife Service biologist Wendy Walsh, which is leading to “changes to the predation pressure that the birds face when they’re on their breeding grounds.” If the predators that used to dine on lemmings – including snowy owls and a number of other birds – can’t get them, they may start to prey on red knots instead.
Meanwhile, there’s also the encroachment of sea-level rise on the birds’ habitat, said Walsh. As a result, the Rufa red knot has now made history – it is the very first bird listed under the Endangered Species Act with climate change cited as a “primary” reason for the listing.
