Subject: [Tweeters] Red Knots and Horseshoe Crabs
Date: Feb 6 12:54:17 2008
From: Henry Noble - hjnoble at igc.org




I'm reprinting below a portion of a fascinating article from Delaware Audubon online at:
http://www.delawareaudubon.org/conservation/hscrab_workshop.html
Henry Noble
- - - - - - - - - -
The lives of two unlikely creatures ? an ancient "living fossil" called the Horseshoe
Crab and a delicate shorebird called the Red Knot ? are intimately intertwined. So
are their futures, and the future doesn't look good.

Why is the Red Knot so threatened?
It all starts in the Delaware Bay, the largest spawning area in the world for the ancient Horseshoe
Crab. Every May, the Horseshoe Crabs come to Delaware Bay beaches to lay their eggs. At the
same time, shorebirds ? including the Red Knot ? use the Delaware Bay beaches as a food
stop on their annual migration from South America to the Arctic.

According to DNREC's Stew Michels several studies have shown declining Horseshoe Crab populations.
Although he said the studies "are not definitive," they show a big population drop in the 1990s and
fairly stable population numbers for the past four years. He added that "no surveys indicate
increasing populations."

Even more important, according to Dr. Niles, there are significant declines in horseshoe crab
eggs on the New Jersey beaches.

Delaware Bay is the last stop for the Red Knots en route from their winter home in Brazil to
their summer home in the Arctic. The birds arrive at the Delaware Bay beaches at very low
weights, he said, lower than at any other stopover. "They have to double their body weight,"
Dr. Niles said, "and the only nutrient they can use is Horseshoe Crab eggs."

His studies have shown a decline in the birds ability to gain the necessary weight. He said this
could be due to later arrivals or to decline in the Horseshoe Crab eggs. He added that the best
studies seem to indicate the decline in eggs is the major problem. This results in lower
productivity among the birds, and more deaths during the migration. The Red Knot now
has a 56% survival rate.

"The number of Red Knots in South America has fallen in half," said Dr. Niles, "and most of the
decline has occurred in the past four years." He estimated the current population at
between 40,000 and 50,000 birds.
>snip<
? Report by Fred Breukelman
Delaware Audubon Internet Communications Chair