The "flags" on the Red Knots show where they have been.
Citizens of every country in the world proudly fly their nation’s flag. Flag colors are universally bright and bold evoking the strong emotions of love and devotion all feel for homeland. One can observe the tears of joy and pride that people from all over the world shed when they see their country’s flag flying in front of the United Nations building in New York, and who can doubt the sincerity of flag wavers supporting their nation’s athletes at the Olympics. But did you know that some birds also carry flags, not as symbols of national love and devotion, but rather to show, in a manner, where they have been? Something like a tourist pin collected at some distant travel location.
Red Knots sometimes collect these travel flags. They breed in the High Arctic and winter in Tierra del Fuego, Argentina, a migration of over 9,000 miles. Along the way, they stop off to re-fuel, and pick up flags to help researchers follow their life cycles. In recent years, some Red Knots have been foregoing the long flight to Argentina and have been wintering in Florida, where they can be found at Merritt Island National Wildlife Refuge and on Sanibel Island. Most of the banding and travel flag placement is done in Argentina on their wintering grounds (orange flags), in the Delaware Bay, a prime stop-over on their migration north (lime green flags), and in Canada on their breeding grounds (white flags). Some birds also carry a silver U S Fish and Wildlife band as well.
The winter plumage Knot pictured here (right) sporting “JL4” was photographed on the causeway linking Sanibel Island to the rest of Florida. The remaining photos were taken on Reeds Beach, a famous stop-over for Red Knots on the Delaware Bay just north of Cape May, New Jersey. One Knot (below) has collected all four travel flags – white “KH,” orange, green and silver. Another pair of Knots, one in full breeding plumage, and one still molting into that plumage, walks past a Horseshoe Crab that gave its life after spawning and depositing the millions of eggs that the Knots feed upon to refuel for the remaining leg of their trip to the arctic tundra. The dark horizontal lines in the photo (bottom) near the crab shell are horseshoe crab eggs washed up onto the beach by the tide.
Red Knots leave their Tierra del Fuego wintering grounds and fly non-stop to the Delaware Bay, timing their arrival there to coincide with the short Horseshoe Crab spawning season which occurs in late May of each year. They arrive exhausted, emaciated and in critical need of food. They gorge themselves for several days on the crab eggs, regaining as much as ten per cent of their body weight a day, building up fat reserves for the next flight to the arctic tundra.
Unfortunately, Horseshoe Crabs have been severely over-harvested for the past ten to fifteen years for fertilizer and fish bait and the decline in Horseshoe Crabs has resulted in a serious Red Knot population loss which some estimate to be as high as ninety percent of their former numbers. Some researchers also believe global warming is impacting their high arctic breeding grounds, but more study needs to be undertaken in this area. For more information on Red Knots and Horseshoe Crabs see this US Geological Survey release.
Perhaps the Red Knot is evolving, and more of them will winter in Florida each year instead of making the long flight to Argentina. It certainly seems to me that we see a few more each winter in Florida than the year before. Only time will tell. In the meantime, enjoy them while we can and continue to look for their little flags that signal to us that they are travelling as they should. (7/5/2012)