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Posts Tagged ‘Delaware Bay Shorebird Project 2015’

2015 Horseshoe Crab Spawn and Shorebird Migration on Delaware Bay

Wednesday, May 20th, 2015
An Update on This Season’s Horseshoe Crab Spawn and Shorebird Migration, Ten Days In

By: Dr. Larry Niles, LJ Niles Associates LLC

Thousands of shorebirds now fill Delaware Bay’s beaches and marshes in a determined effort to regain lost reserves with free-for-the-taking fatty eggs of the horseshoe crab. The crab spawn began ten days ago and has gained momentum over the last week as the volume of eggs grows like a well-funded savings account. The eggs surface as each new female crab digs up egg clusters laid by other crabs or as wind-driven waves pound the always-fluid sandy beaches. At least 8,000 red knots slowly get fat on the eggs scattered on New Jersey’s Delaware Bay beaches.

Eggs on Beach

Eggs on Beach

Both crabs and birds are the beneficiaries of the increasing number of beaches that are highly suitable for egg-laying. In October, 2012, Hurricane Sandy ravaged two-thirds of New Jersey’s best crab-spawning beaches, its strong westerly winds lifting sand and spreading it far from the sea’s edge. Left behind was a jagged sod bank, completely unsuitable for horseshoe crab breeding. The mucky sod starves eggs of oxygen or gasses them with hydrogen sulfide, the by-product of decaying mud.

 

The American Littoral Society, Conserve Wildlife Foundation of New Jersey, the U.S. Fish and Wildlife Service and the National Fish and Wildlife Foundation came to the rescue, restoring many of these beaches to a condition superior to that before Sandy. The restoration team even repaired damages that predated Sandy — beaches with tons of rubble that entrapped crabs in nasty concrete, killing them by the thousands. Now beaches like Thompson’s Beach and Fortescue Beach join the growing number of delicate sandy strands that provide excellent spawning habitat.

Thompsons Beach Before and After

Thompson’s Beach Before and After Restoration

This week, eggs can be found in many places on the New Jersey side of Delaware Bay, and the birds have the freedom to move to those that best suit them. Earlier this month, strong northwest winds drove red knots from the Reeds Beach area to other, more northerly, beaches that saw good crab spawning — beaches that also provide shelter from the winds. Now that the wind and sea have calmed, the birds have returned to the Reeds Beach area, less than 20 miles away, and have resumed gorging on the plentiful eggs that built up in their absence.

Early Morning Shorebirds on Delaware Bay

Early Morning Shorebirds on Delaware Bay

If one were to look for any cloud on the Delaware Bay shorebird horizon, it would lie in the lack of any evidence of horseshoe crab recovery. The current, reduced, population of crabs spawned eggs in great numbers early this May because of a spike in the water temperature, a consequence of unusually warm weather.  So far the promise of this early spawn is holding, and crabs continue to spawn in good numbers. But will it hold until the end of May?

Crabs in Slew

Crabs in Slew

If not, the readers of this blog will witness the outcome. The graph below, developed by long-time team-member Dick Veitch tells the story of a past egg failure. In the early 2000’s, although the population of shorebirds had not yet declined to its current number, the crab population had already fallen to its current number, crushed by the onslaught of a poorly regulated fishing industry.  In those years, all the horseshoe crabs that could spawn had finished by the third week of May and egg densities on the bay plummeted. The birds crammed into the few beaches with eggs like Mispillion Harbor, Delaware, so densely that the beach reeked of off-gassing urinary ammonia.

 

But the number of eggs there was not sufficient to feed the still-large shorebird populations and birds failed to reach a weight – about 180g for red knots — suitable for their journey to the Arctic and subsequent breeding. Where once 80% reached the “good” weight, only 5% did in 2003 (see the second graph).

Percentage of Red Knots Reaching 180 Grams

Percentage of Red Knots Reaching 180 Grams

The percentage has improved thankfully, but only because the number of shorebirds have fallen over the last 10 years, bringing a balance of sorts. Hopefully, with the new beaches, the new protection afforded by the red knot listing and the growing number of volunteers taking part in conservation of the crab and birds, this kind of disaster is behind us.

We shall see.

 

Learn more:

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

2015 Delaware Bay Shorebird Project Continues!

Sunday, May 17th, 2015
Another Season of the Delaware Bay Shorebird Project Underway

By: Dr. Larry Niles, LJ Niles Associates LLC

The value of a shorebird stopover like Delaware Bay can be seen in the shaky cam movie by this author.  Red knots – some recently arrived after a grueling 6,000-mile flight over 6 days of continuous flying – arrive on the Bayshore desperate for food. Over the last 10,000 years, the species has evolved to fly directly to the Bay to feed on the eggs of the horseshoe crab.

The 450-million year-old crab – which is actually in the spider family – crawls ashore and lays pin-sized eggs about 6 inches deep in the sand. When there are many crabs, as here on Delaware Bay, one crab often unearths the eggs of another. Thus they leave millions of fatty eggs on the surface, offering an energy-rich, soft feast for the starving birds. In turn, we get to watch the birds racing for an egg ‘hot spot’!

The birds often arrive beyond depleted. A normal weight for a knot is 130 grams.  Many arrive on Delaware Bay below 100 grams, the equivalent of a human in the throes of profound starvation. But when the birds fly north from the coast of northern Brazil, there’s no turning back. Once they go, they must go all the way.

Map of geolocator track of a South American wintering  red knot

Map of geolocator track of a South American wintering red knot

This year, migrating shorebirds faced a freak tropical storm that could have forced them out to sea, far off-course.  In severe cases, some birds with no remaining fat reserves even metabolize their own muscles, like airplanes throwing out vital equipment to stay aloft. Storms can also prevent birds from lifting off on migratory flights. They are capable of detecting atmospheric pressure changes and can just stay put until a storm passes. We think this is what happened this week when a storm, followed by a strong cold front and consequent northwest winds, prevented a movement north.

The sum of these challenges was lower than normal shorebird numbers during the first week of the stopover. The Heislerville impoundments support a good number of short-billed dowitchers and dunlin, but these species usually arrive earlier than the others and probably came in ahead of the adverse winds. Yet there are very few ruddy turnstones, sanderlings and semipalmated sandpipers on the Bay.

Short bill dowitcher (c) Jan van der Kam  from Life on Delaware Bay

Short bill dowitcher (c) Jan van der Kam from Life on Delaware Bay

The one exception on the Bay is the red knot. At first, we thought that only about 1,000 red knots had arrived in and around Reed’s Beach. Then Jerry Binsfeld and Peter Fullagar, Canadian and Aussie members of our team, found an amazing 7,000 knots at Gandys Beach on the northern Bayshore in New Jersey. Very likely, these are short-distance migrants, coming in from wintering areas in Florida, Georgia and the Caribbean.

Red Knots on Fortescue

Red Knots on Fortescue

Our catch results support this working hypothesis. The knots we caught at Fortescue were at higher weights than normal for this early part of the season, which would be expected if fewer very thin long-distance migrants were part of the average.

The graph shows the weight relative to previous years.

The graph shows the weight relative to previous years.

The histogram shows the distribution of all the birds weights in the catch.

The histogram shows the distribution of all the birds weights in the catch.

Learn more:
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.

2015 Delaware Bay Shorebird Project Begins!

Tuesday, May 12th, 2015
Another Season of the Delaware Bay Shorebird Project Underway

By: Dr. Larry Niles, LJ Niles Associates LLC

Our 2015 Delaware Bay Shorebird Project began on one of the hottest early-May weekends in memory. Clive Minton, an English-expatriate Australian, and I began the project with an early morning survey of each bay beach – Reeds, Cooks, Kimbles, Pierces, Rutgers, Norburys, Villas – dripping sweat and swatting biting gnats as though it was early June, not early May. The sudden burst of summer weather warmed the bay waters, triggering our first horseshoe crab spawn providing sufficient eggs for newly arriving birds.

Delaware Bay Team 2015

 

The birds, on the other hand, followed a more normal schedule. We counted only 400 knots, a smaller number of ruddy turnstones and, surprisingly, no sanderlings. We know the birds are en route; Pat Leary in Florida and Fletcher Smith in Georgia report good numbers of knots, but the birds appear stuck because of the unsettled weather and the rare occurrence of a tropical storm making landfall in North Carolina over the weekend. Soon enough they will come.

Red Knot Photo by: Pat O'Leary

Red Knot Photo by: Pat O’Leary

The warm weather and the abundant crab spawn bode well for the birds – we want the early bird to gets eggs.  But they point to one of the many difficulties facing the red knot and other shorebirds. Will the insidious effects of climate change unravel this elegant machine that provides horseshoe crabs eggs just at the time Arctic-nesting shorebird need them to fly on to their breeding areas?

Horseshoe Crab Eggs

Horseshoe Crab Eggs

Horseshoe Crab Eggs

Horseshoe Crabs Spawning

Our project is 19 years old and so provides a perspective virtually unique among wildlife projects. A long-running project of this kind has many advantages, not the least of which is the human family that has formed around our love of birds. We have nearly the same core team in 2015 as we did in 1997, losing and gaining a few team members as time marches on, but always maintaining an esprit de corp, a common purpose, a lasting bond. The shorebirds, the crabs and the many people who love the Delaware Bay owe a debt of gratitude to this team of intrepid researchers.

Photo by: Christophe Buidin

Photo by: Christophe Buidin

The project’s longevity also creates a perspective rare in the world of bird study. Over 19 years we have seen the collapse of the horseshoe crabs; the dramatic free fall of the red knot that resulted this year in a federal listing as Threatened; the rise of irresponsible commercial exploitation of the natural wealth of the bay; a devastating hurricane and more. And yet each year the birds arrive, the crabs spawn and our team coalesces from every corner of the world. Despite the problems and all the concern, the system persists.

 

But how long will the system persist?

 

The challenges faced by the birds grow every year. They cling to this amazing migratory bird like barnacles on a wooden boat.  Crabs have not recovered from the devastating overharvest of 15 years ago. The international drug cartels still drain the blood of crabs for the valuable chemical lysate without any responsible management. All the while shorebirds, the red knot in particular, face growing threats from climate change: more frequent storms, destroyed coastal habitat, rapidly-changing arctic tundra habitats.

Lysate Industry

Herein lies the value of a long-term study. This season’s unprecedented early spawn and warm weather could be good or bad.  Either way, by season’s end, the team’s dedication, skill, and plain hard work means we will know what happened and what it means compared to 18 other years.

Early Red Knots

Early Red Knots on Baycove Beach on Delaware Bay

 

Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.