Red Knot, Horsecrab Populations Continue to Decline in NJ

[Donna]

REEDS BEACH – There is no evidence that either the Horseshoe Crab or Red Knot population is increasing along Delaware Bay.

The amazing story of the Red Knot arriving each year on Delaware Bay shores from southernmost Argentina at the same time Horseshoe Crabs are coming out of the water to lay their eggs has been repeated for ions.
The long and short of it is the Red Knots feed on the eggs here, rests a week or two, gain a considerable amount of weight and then fly to the Canadian Arctic Circle to raise a family. In the last decade, the number of Horseshoe Crabs has been decreasing meaning fewer eggs for the birds to consume on the shoreline, lessening their chances of having the energy to fly to the Arctic Circle.

Each year, scientists from as far away as Australia and England take over two rental houses on Reed’s Beach and study Red Knot/Horseshoe crab numbers at the peak of the phenomenon, a full moon in late May or early June. The crabs come out of the bay in the highest numbers under the full moon.

“The crab spawning is happening at the right time in relation to the bird stopover,� said Humphrey Sitters, a scientist from the University of Exeter in England with the International Wader Study Group.

He said in England, shore birds are called waders. Sitters said he has been coming to Reed’s Beach to study the birds for 14 years.

In 2008, there was a mismatch. Horseshoe Crab spawning was too late and the birds did not get enough food, said Sitters.
“The evidence seems to be there has been no real change in the size of the crab population,� said Sitters.

“In the distant past, before the overharvesting of the crabs, there were so many crabs and they spawned for such a long period of time, there were always plenty of eggs but we’ve now got the situation where the timing is critical,� he said.

In 2009 and this year, the birds and crabs have arrived at the same time. He said there is some evidence this year at least part of the Red Knot population was delayed in early May in Patagonia, the southernmost portion of South America in Argentina.

Horseshoe Crab numbers reached a peak in 2006-2007 and have since declined, according to Virginia Tech data. Overharvesting by commercial fishermen who cut up the crabs for bait to catch conch and eels has reduced the crab population greatly since 1990.

“If anything, the adult crabs have declined over the last three years (2006-2009) but on the other hand, there seems to be an increase in immature crabs,� said Sitter.

The scientists conduct counts of the number of Red Knots along the bay. Last year, the count increased to about 25,000 birds. He said this year he believed the peak count would be around 17,000 Red Knots.
The population has dropped from a count of 50,000 birds in 1998.

In some years, all of the Red Knots arrive with no departures to the Canadian Arctic which reflects the total number of birds that come to Delaware Bay. In other years, some birds depart before others arrive affecting the peak count.
Some Red Knots stop off at other sites on the east coast such as the Virginia barrier islands. He said where they stop may be based on the food supply at both locations.

For the last several years, the Red Knot and Horseshoe Crab population “have been sort of bumping along the bottom,� said Sitter, with no major change in either population in the past four to five years.

He said counts of the Red Knot are conducted in its wintering area in Tierra del Fuego at the southernmost tip of South America where the number of birds has been “bumping up and down.�
Sitters said the winter population has averaged in the 16,000 to 17,000 range.

“There is no evidence of a recovery of the Red Knot population at all,� he said.

A full moon occurred on May 26 bringing a lot of crabs from the bay to spawn both at Reed’s Beach and on beaches in Villas. On May 27, this reporter saw one Red Knot among a huge gathering of sea gulls on Reed’s Beach eating tiny, green Horseshoe Crab eggs. Those who had been watching bird activity for several hours from the observation platform reported seeing an occasional Red Knot.

Both New Jersey and Delaware placed moratoriums on Horseshoe Crab harvesting in 2006 and 2007.

[Donna]

New Jersey scientists knew red knots were world-class flyers that make epic migrations from pole to pole each year.

Now research suggests the little robin-sized birds make part of this odyssey in one incredible bound.

One bird studied this year left Brazil on May 19 and arrived at the Delaware Bay on May 23.

That's four days and nights of nonstop flying across more than 3,200 miles of rainforest and open water without pause for food, water or sleep. That is a longer nonstop flight than any offered by Atlantic City International Airport.

"It's crazy. After a night of losing sleep, I can't even think straight," said Amanda Dey, a principal zoologist with the state Department of Environmental Protection.

She and her husband, biologist and consultant Larry Niles, have been studying red knots for the past 14 years. Each spring the birds fly from New Jersey to their nesting grounds in the high arctic along Hudson Bay. In the late summer, most fly the length of two continents to the tip of South America, where they spend the winter in Tierra del Fuego, Spanish for the "land of fire."

Finding red knots in Cape May County is easy.

The birds gather by the thousands along the same beaches of Middle and Lower townships, where they fatten on the eggs of horseshoe crabs that spawn each May in Delaware Bay.

The birds are so predictable that the state fences off the same beaches every year in anticipation of their arrival.

But finding the rare shorebirds in Canada is much harder. Imagine 16,000 birds scattered across thousands of square miles of lichen-covered rocks, each of which vaguely resembles a bird on a nest.

"With that red breast, you would think they'd stick right out on a barren rocky landscape," Dey said. "But they are super-camouflaged. They nest on mossy plants. They blend right in with the vegetation. It's not easy to find them at all when they're on eggs. They're virtually impossible to find."

New way to track

When Niles first conceived tracking the birds' migration for the DEP in the 1990s, he used VHF radio transmitters to locate them by airplane at their Southampton Island nesting grounds, not far from where polar bears roam. But the transmitters were heavy, placing a burden on the birds, and had a weak 8-mile signal that required long, expensive days of airborne searching, he said.

Last year, the researchers decided to try a new tracking device called a geolocator, a little green flag lighter than a paperclip that is attached to a bird's leg. The geolocator works like a sextant, recording the rising and setting sun to determine the bird's position on the globe.

The geolocators are so effective that they can tell researchers which birds nested. The parents blot out the midnight sun when they incubate their eggs.

The study is giving scientists a greater appreciation both for the birds and their close relationship with horseshoe crabs.

The prevailing theory about red knot migration suggested they hopscotched up and down the coast, resting or even feeding between flights. But the study shows some birds are making longer and more perilous journeys.

"We figured they flew along that long South American coastline. But with the geolocator birds, they make a straight flight across the Amazon," Dey said.

Since red knots are not tree-dwellers and do not swim, they cannot stop for a breather in the equatorial jungle like songbirds or rest on the ocean's surface like gulls. And while the distance might be 3,200 miles as the crow flies, coastal storms can make the trip 4,000 miles or more for red knots.

"It's transformative in a way," said Niles, who has made annual trips to the arctic and South America in pursuit of the shorebirds.

"The common view is that birds leave here and go there - a kind of straight-line, mechanical flight not unlike when we get on an airplane and go someplace," Niles said. "What we are seeing instead is a lot of drama. When you look at the migration of individual birds, you see how desperate it turns out to be."

The problem with geolocators is researchers have to recapture the banded birds to recover the data. So far, the New Jersey team has recovered three of several dozen flags they attached last year. One bird departed from New Jersey last year and flew east 300 miles, apparently to avoid a storm front, before aborting the trip and returning to New Jersey to give it a second try, Niles said.

"Their migration is even more difficult than we thought," Niles said. "When they encounter bad weather, they can get blown hundreds of miles out to sea and still have to make it to land."

Importance of bay

Red knots have declined in population from more than 80,000 in the 1980s to just 16,000 last year. The good news is the birds have not lost any ground. Researchers counted about the same number in May, Dey said.

But the geolocator is confirming previous findings that the Delaware Bay is a crucial spring rest stop. The birds arrive starving and emaciated but immediately begin gorging on eggs, nearly doubling their weight in a matter of weeks to resemble flying Nerf footballs.

"It's the great equalizer," Dey said. "If they arrive at low weight, they can make up the difference in the Delaware Bay. If they encounter snow or a lack of food in the arctic, they can survive because they made weight in the Delaware Bay. It is a big buffer for them."

Red knots are one of several local shorebirds that depend on the bay and have suffered similar declines. Researchers speculate the birds cannot find enough crab eggs to make weight for the trip. States from Virginia to Massachusetts responded by placing restrictions on the harvest of horseshoe crabs.

New Jersey took the most drastic step, banning all fishing for crabs since 2008. Dey said she would like other states to do likewise.

"What we really need is enough food for a restored shorebird population - back to the 90,000 red knots and 1 million shorebirds," she said. "That's the level we need to be to restore the bay. I don't think the current horseshoe crab population can do that."

And the longer it takes for horseshoe crabs to recover, the longer local fishermen will have to wait to resume their harvest, she said.

The researchers plan to catch more birds on their southbound migration later this year in Florida.

The flags will give them a day-by-day record of a bird's movements around the world.

[MAK]

Thanks piglet! New 'puter yet?

[Donna]

Thanks piglet! New 'puter yet?

KNOT yet piggy...won't even be sent out til the 16th...

[valhalla]

Thanks piglet! New 'puter yet?

KNOT yet piggy...won't even be sent out til the 16th...

Told Donna yesterday that I've had an order (biggun) in the works for over a month.  Arriving piecemeal.  Of course, commercial vs consumer product line.  The consumer line does move a bit quicker.

[Mirta]

New Jersey scientists knew red knots were world-class flyers that make epic migrations from pole to pole each year.

Now research suggests the little robin-sized birds make part of this odyssey in one incredible bound.

Hi Donna!
We have put here several geolocators this season (see my bad picture...) for that project.
I`ve got reports from my friends in Delaware Bay now, that several birds arrived from here to Florida and Georgia`s beach in 9, 11 and 12 days! They are amazing creatures!!

Mirta

[valhalla]

Big Wow Mirta!

[huddiecat]

This year we were at Reeds Beach mid-May and were hoping to see the Red Knots arrive, but were a bit early for the big arrival.  A couple of years ago we were at Cape May as the Red Knots and the Horseshoe crabs were in full force.  It was awesome to watch them fly, land, then take off again!  We had a great chat with one of the Red Knot "watchers" at Reeds Beach. 

Thanks for posting information on them.
Suzanne 

[Donna]

This year we were at Reeds Beach mid-May and were hoping to see the Red Knots arrive, but were a bit early for the big arrival.  A couple of years ago we were at Cape May as the Red Knots and the Horseshoe crabs were in full force.  It was awesome to watch them fly, land, then take off again!  We had a great chat with one of the Red Knot "watchers" at Reeds Beach. 

Thanks for posting information on them.
Suzanne 

How cool you got to see the Knots & Crabs. Thanks