Working in the low light of the midnight sun, a scientist at the top of the world reveals why the Red Knot is a marvel of biological engineering
By Clare Morrison | Published: 2/15/2011
Bleary-eyed early on a May morning, I sit in the waiting area of the military airport at Trenton, Ontario, and bide my time. I’m traveling with my father, Guy Morrison, a senior research scientist with Environment Canada, and he and I know the drill: hurry to check in by 4 a.m., then wait until 7 a.m. to take off.
We don’t mind. Soon we’ll be on our way to one of the world’s most fascinating places, one my father knows well: a tiny speck of civilization known as Canadian Forces Station Alert.
Located at the northern tip of Ellesmere Island, CFS Alert is the northernmost permanently inhabited outpost in the world. Closer to Moscow than to Ottawa and cloaked in total darkness each year from October 10 to March 1, it is a cold, barren place most of the time, occupied by a handful of hardy weather, signals-intelligence, and civilian personnel and reached only by military aircraft and chartered jets.
Yet for two and a half months in the part of the year warmed by the midnight sun (the average temperature during July, the hottest month, is 37.9°F, or 3.3°C), the island becomes the summer home of a charismatic, robin-size shorebird famous for making long-distance migrations — the Red Knot (Calidris canutus).
The bird is a familiar sight on all coasts of North America. The subspecies known as C. c. roselaari winters in the Pacific Northwest of Mexico and stops over in Grays Harbor, Washington, and the Copper River Delta while migrating along the Pacific coast to northwestern Alaska and Siberia. Another, C. c. rufa, gathers in Delaware Bay on its way from South America to the Canadian low arctic. Ellesmere Island, in the high arctic, is the breeding grounds of yet another subspecies, C. c. islandica, which flies there (and to Greenland, too) from western Europe. It is the focus of my father’s research, his passion, and the reason for our trip.
25 years: Age of the oldest Red Knot
The oldest recorded Red Knot was an adult when it was banded in August 1968, along the large bay on the east coast of England known as the Wash.
Since the bird could not have hatched later than July 1967, it had to be a quarter-century old when it was recaptured, at the same location, in September 1992.
Most Red Knots live much shorter lives, no more than 7-8 years.
Source: Committee on the Status of Endangered Wildlife in Canada, 2007. COSEWIC assessment and status report on the Red Knot Calidris canutus in Canada.
He has been making the journey to CFS Alert, where he is known as “Birdman,” for 26 years. I’m joining him as a research assistant. His mission: to catch, band, and observe knots, the better to understand the striking physical transformations they undergo during their annual migration cycle.
“Red Knots,” he tells me, “are amazingly adapted to breeding in the arctic. You look out and see what appears to be just a simple bird feeding on the shore, but really what you’re looking at is a marvel of biological engineering.”
Flying to Ellesmere
Our 2,600-mile flight (4,200 kilometers), on a C-130 Hercules turboprop plane, requires an overnight refueling stop in Thule, Greenland, and takes about seven hours. The knot’s 2,800-mile journey to Alert (4,600 kilometers) takes about a month. After leaving Europe near the end of April, it stops in Iceland or northern Norway for three weeks. Then it flies on to Ellesmere, arriving in the last days of May and the beginning of June.
Its two long, nonstop flights sandwich the most important part of the annual migration: the refueling stop. During it, the bird transforms into a flying machine. Body parts that won’t be used while flying — the stomach, leg muscles, and other organs — decrease, while what you might think of as pieces of the bird’s flight equipment — the heart, its muscles, and fuel stores — increase, leaving the Red Knot in a condition that’s exquisitely adapted for migration.
Even more amazing, once the shorebird arrives in the arctic, it transforms again, from a flying machine into a breeding machine. That is, it uses fat and muscle protein put on in Iceland to re-grow the stomach, intestines, liver, gonads, and other organs that decreased before takeoff. And it does this at a time of year when snow may still cover the ground and little food may be available. When that’s the case, the leftover fuel also acts as an energy source that enables the bird to survive until conditions improve.
Long-term data collected on Ellesmere make clear how important such extra body stores are. In the 1970s, Morrison worked in Iceland banding knots. At the same time, particularly bad weather made for difficult breeding conditions in the north. Knots that achieved above-average condition before leaving Iceland were seen again in later years; that is, they survived the harsh breeding conditions. Birds that did not reach a heavier take-off weight didn’t fare nearly as well. As my father says, “It was survival of the fattest!”
This insight has special relevance to understanding the conservation crisis that knots of the C. c. rufa subspecies have experienced in Delaware Bay. Like Iceland, the bay is the birds’ last stop before heading to the arctic. Overharvesting of horseshoe crabs, whose eggs form the knots’ principal food source, has resulted in many birds not reaching an adequate take-off weight. Consequently, they lack the critical extra body stores needed for survival and breeding.
Research has shown that Delaware Bay’s knots pay a considerable survival penalty for failing to find enough to eat. “Their survival plummeted from about 85 percent to around 56 percent,” Morrison says. “This situation has undoubtedly contributed to the spectacular and disastrous decline of the rufa population by some 75 percent since 2000.” (See sidebar: Counting knots on two continents.)
Determining the percentage of birds that survive from one year to the next, or assessing the rate at which a shorebird gains or loses weight during migration, is essential to conserving a species or subspecies, and it can be accomplished only one way — by catching birds. To do that on Ellesmere Island, you need two items: local knowledge and a rocket net.
“In general, catching knots here in the high arctic is a special challenge,” my father explains to me, “because the birds are spread out over large distances on the tundra.”
Red Knots of the Eastern Hemisphere
C. c. canutus
Breeds in the Taymyr Peninsula in northern Russia and migrates to western Europe and then to western and southern Africa.
C. c. rogersi
Breeds in the Chukchi Peninsula in eastern Siberia, and winters in eastern Australia, in New Zealand, and on the eastern coast of India.
C. c. piersmai
Recently split from C. c. rogersi. Breeds in the New Siberian Islands, located north of the Siberian coast, and winters in northwestern Australia.
Red Knots of the Western Hemisphere
C. c. roselaari
Breeds on Wrangel Island in Siberia and northwestern Alaska and winters in the Pacific Northwest of Mexico. (There is uncertainty over the taxonomic status of two other biogeographic populations of knots presently designated “roselaari.”)
C. c. rufa
Gathers in Delaware Bay each spring. Breeds in the Canadian mid-arctic and winters at the southern tip of South America.
C. c. islandica
Breeds in the northeastern Canadian high arctic and Greenland and winters in western Europe.
A wastewater stream below the military station at CFS Alert, however, offers researchers a special opportunity. The only open water on the island at this time of year, it’s a natural magnet for birds, especially just after they arrive, when they’re still in groups before dispersing to nesting territories. So that’s where we plan to set our trap.
We haul the heavy equipment through the snow, drive metal stakes into the frozen ground to secure one edge of a bulky, 30-by-20-meter net, and furl the remainder into a long bundle. Then we position five rockets so they’ll carry the net high over the birds. Once that’s done, all we need to do is wait for the knots to congregate in exactly the right spot.
This often requires a bit of what shorebird banders the world over call “twinkling,” a gentle and very slow herding of the birds into the catching area. The slightest misstep will flush them, so this can’t be rushed.
When the knots are finally in position, Morrison radios that we’re ready to fire. It’s a moment filled with anticipation — like watching a toaster and knowing it’s going to pop. Three… two… one… bang!
My adrenalin surges as the rockets and net soar over the birds. We race to the catch site with our bird bags in hand and carefully remove 15 knots from the net.
Afterward, in the lab, we measure, weigh, and take a small blood sample from each one. DNA in the blood will reveal the knot’s sex, while blood metabolites will suggest its metabolic state — key to understanding the physiological changes that take place after and before migration. Then we place a metal band and four plastic bands on the legs, taking pains to use unique combinations of colors so each bird can be identified from a distance later on.
Like shorebird researchers throughout the hemisphere, we also use a colored plastic leg flag to indicate where the bird was banded. Banders working in Argentina affix orange flags. In Chile they use red, in Brazil blue. Birds wearing green leg flags have been banded in the United States. Our leg flag is white, showing that the bird was banded in Canada. (Morrison usually catches between 50 and 80 knots in a season.)
We keep the knots for only a short time before releasing them. Soon they’re back on the tundra, setting their sights on the reason they’re here: breeding. By the beginning of June, we notice males displaying and singing their melodious mating calls. Once paired, and once a breeding territory has been established, the male makes a number of scrapes in the ground — each a potential nest — and the female chooses the one she likes best.
Red Knots lay a four-egg clutch that is incubated by both parents for 21-22 days. After the eggs hatch, the female sticks around for a day or two but then heads off to feed and fatten before beginning her migration back to Europe, leaving the bulk of the rearing duties to the male.
The ensuing 18-day period until fledging is a vulnerable time for the chicks. If an arctic fox, Long-tailed Jaeger, arctic wolf, Glaucous Gull, or other predator comes looking for an easy meal, the male will alarm and attempt to distract it with what ornithologists call a “rodent run.” He will hunch himself into a ball and run away from the chicks while making a high squealing noise. It’s quite the sight seeing a Red Knot turn into what appears to be a rat!
Counting knots on two continents
Guy Morrison’s passion for shorebirds has carried him not just to the top of the world but to the tip of South America.
Between 1982 and 1986, he and a colleague flew almost the entire coastline of South America, about 17,000 miles, in search of the winter grounds of shorebirds that breed in North America.
Flying just 50-80 meters above the ground in a single-engine, low-winged aircraft, the pair counted almost three million shorebirds and, just as important, showed that the birds did not spread themselves around the continent evenly but gathered in a few key areas.
In late January and early February of each year since 2000, Morrison has returned to the coastlines of Argentina and Chile, wintering areas for the rufa subspecies of the Red Knot, and repeated his aerial surveys.
The counts have revealed dramatic declines. Numbers at Bahia Lomas in Chile, the knot’s principal wintering site, fell approximately 50 percent from 2000 to 2002-03 and 50 percent again between 2004 and 2005. Sites on the coast of Patagonia that used to hold 14 percent of the total now hold only 2 percent. Ninety-eight percent of the birds are now concentrated in Tierra del Fuego.
“Studies in Delaware Bay,” Morrison wrote in 2004, “suggest that increased adult mortality of Red Knots resulting from inability to gain sufficient weight prior to migration to the breeding grounds could account for the magnitude of the observed declines.”
Another tool employed by knots to cope with the challenge of breeding in the tundra is camouflage. Against the tundra landscape, the chicks and adults are almost invisible. On many occasions, I watched birds land, glanced down at my notebook, and then quickly looked back up, only to discover that the birds had seemingly disappeared.
A special wax produced in a gland on the knot’s back plays a key role in enabling the knots to remain undetected. It does so by seasonally changing what it smells like. Knots use the wax year-round while preening, keeping their feathers not only waterproof but also in flight condition. Jeroen Reneerkens, who worked at CFS Alert as a student and is now a shorebird researcher in the Netherlands, showed that the composition of the wax changes during the breeding season. In summer it is much less volatile, or smelly, than in winter.
Would the odorlessness make the birds and their eggs hard for a fox to detect as it sniffed for prey across the tundra? Amazingly, yes. Reneerkens demonstrated that a trained sniffer dog had great difficulty detecting the summer wax but could easily find the winter wax. The adaptations for life on the tundra even extend to a molecular level! No wonder my father describes the Red Knot as a marvel of biological engineering!
When August arrives and the sun gets closer to the horizon, we know that in a matter of days, the window of life and light will close and the tundra will revert to a frozen landscape as hard as iron.
The new generation of knots, along with the adult males, feed like crazy to fatten up and then set off on their long migration back to Europe.
Their departure signals that it’s time for us, too, to head south.
Clare Morrison is a writer and photographer based in Courtenay, British Columbia. Her work has appeared in Canadian Geographic and other magazines. She has participated in bird-conservation projects in Argentina, Hawaii, California, and Iceland as well as on Ellesmere Island.