Flock of Red Knots at Cape May, New Jersey
In one of the stranger relationships in nature, Red Knots and Horseshoe Crabs dance together on the beaches of the Delaware Bay in New Jersey and Delaware for a few short weeks at the end of May each year, and then ignore each other until urges bring them back again the following May. Urges? Actually, the Horseshoe Crabs (left) are there to mate and lay eggs to perpetuate the species, hopefully more eggs than the birds will eat.
The Red Knots, (below left, summer breeding; below right, winter) having carefully timed their arrival from the southern tip of South America, are there to eat all the eggs they can to build up their depleted fat reserves so that they can continue their migration on to the high Canadian Arctic for their summer of mating and perpetuating their species. They rely on the Horseshoe Crabs to provide enough crab eggs for them to gorge upon and rebuild all their fat reserves lost in the first leg of the migration flight. For millennia this converging dance has worked well, as the crabs produced more than enough eggs and their numbers grew; just as the shorebirds were able to eat more than enough to be able to reach their breeding grounds and have all the energy they needed to successfully raise their young and increase their numbers. Happiness reigned.
Then came human Greed. First, in the early nineties, a small number of opportunists discovered that Horseshoe Crabs, ground up, made good cheap plentiful fertilizer. They carted Horseshoe Crabs away by the truck load. Shortly behind them, another group of opportunists discovered the horseshoe crabs made excellent cheap plentiful bait for catching eels, those delightful slippery slimy metaphors for the criminal dregs of our society, that in real life are the tasty parts of Japanese sushi, for which there is a vast Asian market. Many more truckloads of Horseshoe Crabs were carted away. Not surprisingly, the Horseshoe Crab population plummeted, and also not surprisingly, did the Red Knot population: from an estimated 140,000 in the 1990’s to less than 15,000 in the early 2000’s when a state moratorium on harvesting Horseshoe Crabs went into effect.
Since the moratorium they have rebounded to around 25,000, but they are definitely not out of the woods. Tremendous lobbying pressure continues for the lifting of the moratorium and to allow the same small number of opportunists to resume cashing in on the easy pickings.
But human greed is not the Red Knot’s only problem, nature can also create disastrous circumstances. Hurricane Sandy did well publicized damage to New Jersey’s Atlantic beaches, but it also did much, less well publicized, damage to the Delaware Bay beaches where the Horseshoe Crabs and the Red Knots do their annual dance. Strapped New Jersey did not have the funds necessary to restore the Delaware Bay beaches, and it was only a very concerted private effort that raised the funds to do the restoration work in time for the Red Knot – Horseshoe Crab 2013 annual prom. See: http://www.nj.com/news/index.ssf/2013/06/red_knots_shorebirds_feast_on.html.
While virtually the entire world’s population of Red Knots passes through Delaware Bay on its annual migration north, a small part of the population has begun to change its pattern and fly to Florida for the winter, rather than make the entire journey to Tierra del Fuego. They can be found wintering at Merritt Island and also at Sanibel. Perhaps this is nature’s way of accommodating the changes the species is encountering to ensure its survival.
I don’t expect that we will ever see the Delaware Bay beaches undulating with Horseshoe Crabs and Red Knots as we did in the 1950’s and 60’s when there were no houses on the beaches or road access as there is now, and it was very difficult to even get to the beaches to view this annual spectacle, which then continued as far as the eye could see; but we can hope that with enough dedicated conservation care and concern, future generations will continue to thrill at the spectacular annual Red Knot – Horseshoe Crab prom.
The photos depict Horseshoe Crabs mating, and those that perished, presumably after mating, as well as Red Knots in breeding and winter plumage, and in flight. The beaches are littered with Horseshoe Crabs shells for miles. (right)
For a short video of shorebirds feeding on Horseshoe Crab eggs, see: http://youtu.be/f6bKqolJAt8
For an excellent, comprehensive 50 minute PBS film on the two species interaction, see: http://www.pbs.org/wnet/nature/episodes/crash-a-tale-of-two-species/video-full-episode/4772/.