Red knots from the “northern” wintering population have spent the last eight months in the southeastern US and the Caribbean. In early May, this overwintering group is joined by the long-distance migrants coming from southern South America, known as the Patagonian wintering group. The coast of Georgia is host to both populations of this Atlantic Flyway subspecies, known as “rufa” knots.
Red knots and other shorebirds line up in the fading evening sun, waiting for the crabs to finish spawning as the tide drops, exposing the eggs that will feed and fatten the migrating birds.
How many knots, from which wintering population, depend on the Georgia barrier islands during northbound migration? How long do they stay? And how do they use the southeastern resources to gain the weight they need to migrate to nesting areas in eastern Canada? Nobody knows the answers to these questions yet, but a small group of dedicated biologists is trying to learn all they can from the knots by studying them on the remote barrier sands of the Georgia Coast.
Since early April, Fletcher Smith and Beth McDonald, from the Center for Conservation Biology, have been working with Manomet and the Georgia Department of Natural Resources to document the timing of Red Knot migration at specific high-use sites along Georgia’s 100-mile coast.
Beth McDonald and Fletcher Smith, from the Center for Conservation Biology, are studying the northbound migration ecology of Red Knots on the Georgia Coast.
The objective of this study is to estimate the numbers of knots coming through Georgia on their way to nesting grounds in eastern Arctic Canada. The field methods follow a research design developed by Manomet’s partner Jim Lyons, a quantitative biologist with the United States Geological Survey. I had the opportunity join the effort last week, the first week that the long-distance migrant knots reached the Georgia coast. The first knot seen this year, with an orange flag-band (below), was originally banded in Argentina in 2015.
A Red Knot finds a horseshoe crab egg mass and plunges in. Orange UH1 was banded in Argentina and was the first Patagonian bird we saw this year in Georgia.
There is something very special about spring shorebird migration. The birds are at the height of their annual colors and their stunning appearance is matched by the intensity of their behavior. The dull gray and brown winter feathers have been replaced by highly patterned, buff, orange, red, black, white, and blue. The colors of individual birds are reflected in the entire flock, especially when grouped tightly together feeding on an abundant food source, like the eggs of spawning horseshoe crabs or dense patches of small clams.
A Ruddy Turnstone looking very gaudy as it reaches peak plumage. The spade-like bill of these birds allows them to dig into crab nests, even when the sand is dry, giving them an advantage over the softer billed shorebirds they migrate with. Ever wonder why this bird is so ornate? See Shiloh Schulte’s photo below of a nesting turnstone on Coats Island in Canada. It’s all about nesting.
Ruddy Turnstones stand out on the beach, but blend into their rocky tundra nesting habitat very nicely. Try squinting when looking at this photo and bird almost disappears. Photo from June 2014 on Coats Island by Shiloh Schulte.
This time of year, the calm, rather placid, winter attitudes of shorebirds dramatically transform to food-focused, fast paced, sometimes grumpy, and usually aggressive. The birds are on a singular, energy demanding, mission to migrate north and reproduce. The birds move locally, sampling food at every opportunity, looking for abundance, which maximizes food intake and builds the energy reserves they will need in the weeks ahead.
The effort to find the knots becomes a dance with the tides, the weather, the boat, and the constantly moving birds themselves. The knots seek the best foods available, in the narrow window of opportunity during outgoing and incoming tides, when the birds can reach there hidden prey beneath the saturated sand. The birds’ bills need the sand to be wet in order to probe in to find the buried food, like small clams or hidden crab eggs. This means time is of the utmost essence and birds are superb at knowing when they need to be and where. Knots are totally dependent on the shallow pools and saturated sand of the pulsing tide.
Red Knots, Ruddy Turnstones, Sanderlings, Dunlins, and Semipalmated Sandpipers wait for the tide to drop. Nearshore intertidal bars and shoals are critical for these birds and the marine animals that they feed upon. All of the prominent species in this photograph will migrate far, to remote treeless tundra landscapes on islands like Baffin, Southampton, Coats, and King William.
Shorebirds and their ability to migrate on the Atlantic Coast are totally dependent on the birds’ access to marine foods hidden in the sands, silts, and muds that are flooded by tides twice per day. This highly dynamic, thin ribbon of habitat has largely been overlooked for decades by state and federal coastal management authorities. As a result, we have lost the integrity of hundreds, if not thousands of miles of intertidal biological wealth. As a stark example, virtually all of the inlets on the east coast of Florida have been hardened by rock structures to stabilize them, impoverishing the once rich shorebird habitat. We want our coastal sands to stay still, so we create rock and cement armoring to attempt to control our beaches and inlets. We also want wide beaches for recreation, so we pump the sand sediments from the intertidal shoals and bars to recreate eroded beaches. The cumulative result of this activity over the last six decades has eliminated the habitat of for prey species of our migrant shorebirds.
An underwater feast: a Red Knot, a Short-billed Dowitcher, and a Dunlin go deep to find a cluster of horseshoe crab eggs underwater.
As long as we start to understand and the public begins to appreciate how important the intertidal areas of our coast are to wildlife, we can work together to ensure that there will be enough of this beleaguered habitat to support the foods that shorebirds need, so these incredible feathered migrants will continue to persist on our coasts.