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Posts Tagged ‘Sanderlings’

Early days on Delaware Bay – Horseshoe Crabs Just Beginning To Breed as Shorebirds Arrive

Saturday, May 19th, 2018

by Larry Niles

Horseshoe Crabs Just Beginning To Breed as Shorebirds Arrive

 

Delaware Bay horseshoe crab eggs reach sufficient levels to give red knots and other shorebirds a good start on the fat they need to fuel the last leg of their yearly journey in the first week of the stopover ( May 12-19).  Knots need at least 180 grams to fly to the Arctic and breed successfully.  This week we caught birds that weighed 93 grams which is 30 grams below fat-free weight.  These birds had just arrived from a long flight, probably from Tierra del Fuego, Chile or Maranhão, Brazil.  In the same catch, we weighed red knots as high as 176 grams or only 5 grams from the 180-gram threshold.  These birds are probably from Florida or the Caribbean wintering areas and so arrive earlier,  resulting in them having more time to gain weight.  All together it looks like a normal early migration and a modest horseshoe crab spawn, just barely enough for the birds in the bay.

shorebirds in a net

Our team prepares a catch of knots turnstones and semipalmated sandpipers for extraction to keeping cages. The birds will be covered to prevent feather abrasion before extraction (Photo by Stephanie Feigin)

However, we are still short of about half the population.  Our bay wide count won’t take place until next week on May 22 and 26. At this point it looks like we have about 14,000 knots in the bay, of which 8,000 are in New Jersey. In the last 5 years we have had a bay wide population of about 24,000 red knots.  The situation is similar for ruddy turnstones and sanderlings.  The southernly winds of the next few days will almost certainly bring in the rest of the flock by mid-week.

The Stopover Habitat is Growing

 

The condition of the stopover is mixed.

The work of Niles & Smith Conservation Services, Conserve Wildlife Foundation of NJ, and American Littoral Society continues to supply high-quality habitat for horseshoe crabs. We have developed an efficient system for maintaining the essential requirements of a good spawning beach, deep and large grain sand with berm heights that prevent over washing in a way that keeps cost down. First, by creating low oyster reefs to break waves in lower tides, thus protecting beaches from wind waves at low and mid tides.  Second, by placing sand on beaches that typically erode fast losing sands to adjacent creek inlets and the next beach south.  This way we can use one restoration to restore three different places.  For example, Cooks Beach loses sand to South Reeds.

 

restored beach in Delaware Bay

Thompsons beach before and after restoration by American Littoral Society and partners. (Photo by Larry Niles)

Oddly these successes may be contributing to the next big problem for the birds. The state of Delaware has been carrying out much larger scale beach replenishment projects that have added significant new sandy beach for crabs spawning.  At the same time the Atlantic States Marine Fish Commission has failed to deliver on its promise to increase the number of crabs.  The population is still 1/3 below carrying capacity or the number that existed 20 years ago.  The same number of crab divided by more beach equals decreasing crab densities.  Decreasing densities means fewer eggs reaching the surface because crabs are not digging up existing eggs to lay their own.

In other words, we need more crabs.

The Industry Finds New Ways around the ARM Quota

 

But the resource agencies seem perfectly happy to keep killing adult crabs for both bait and bleeding at near historically high numbers. Bait harvests recorded as coming from the bay have stayed the same, however other states such as NY are still taking and landing large numbers of crabs despite having no known crab historic population of their own. Additionally, Virginia states that a crab population still exists in the state, even though most field biologists consider them lost.  The truth is they are very likely taking Delaware Bay crabs and landing them as their own.

The Conservation groups are no longer satisfied with this loose regulation and are calling for regulations similar to those used for Striped Bass.  The Delaware Bay harvest should be restricted to just the quota agreed upon by everyone through the Adaptive Resource Management system.  All other landed crabs should be genetically linked to a source population, and if they do in fact come from Delaware Bay they should be taken out of the ARM quota. No one should be allowed to get away with killing our crabs outside the quota.

Or just stop the senseless killing of these valuable animals as bait for the dying couch fishery.

 

crab eggs graph on Delaware Bay

This graph compares the finding of Botton et al 1994 from horsesoe crab egg surveys done in 1990 and recent counts done in 2017

 

The same goes for the killing of crabs by the companies bleeding crabs.  The industry makes untold millions (the numbers are hidden from the public) but does virtually nothing to conserve the crabs while killing thousands. Their own estimate is well over 65,000 a year, but independent estimates double that.  This killing could also stop because a new synthetic lysate is available and can be used now, potentially cutting the need for natural lysate by 90%.

An Ecosystem Collapse and the Need for More Crabs

 

Why kill such a valuable animal?  It all started because the fishing industries saw little value and figured why not destroy the population until they are no longer economically viable.  Its called economic extinction and sadly it’s a tradition amongst Delaware Bay fishers still carried out this to this day on eels, conch, and other species.  But they didn’t know back in the early 90’s they would wrecking the entire ecosystem.

In 1991, we counted an average of 80,000 horseshoe crabs/meter squared.  Now we count 8,000.  Then the eggs stayed at that level for all of May and June then hatched young at similar densities. In other words, the horseshoe crab was a keystone producer of an abundant resource that maintained the bay ecosystem.  It was not just chance that at the same time the bay has one of the most productive weakfish and blue claw crab fisheries in the Atlantic coast.  Fish populations blossomed with the flush of horseshoe crab eggs and hatched young each year.

Now we must bring it back.  For the birds, for the fish, and for the people who love to bird and fish.

 

storm delaware bay horseshoe crabs

A storm looms over Delaware Bay. The last 4 days have been rain, some intense and cold. The water temperature needs to be 59 degrees or so for Crabs to spawn. On Saturday the 19th the water temperature fell below and the spawn virtually stopped in many places. It should resume with the warmer temperatures of Saturday and Sunday.

We are grateful to the National Fish and Wildlife Foundation and other donors who make this project possible.

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

Scarcity and Abundant – Shorebirds Near the Finish Line on the Delaware Bay

Wednesday, May 31st, 2017

By Dr. Larry Niles, LJ Niles Associates, LLC

Our latest catch of red knots and ruddy turnstones two days ago (May 27) suggests 2017 to be one of the most challenging years for our 20 years of work on Delaware Bay. It challenged the birds for certain.

For example, as of two days ago (May 27), the average weights of red knots remain mired in the mid 160’s when it should be in the 180-gram range. This seems a minor difference but to red knots it means a flight through the cold and often inhospitable north country of Canada and dropping out of the sky never to be seen again or landing and never attempting to breed. We really don’t know for sure what happens to ill-prepared shorebirds, except they are less likely to be seen ever again. In 2017 most birds will be ill prepared.

This histogram of the red knot catch made on May 27, 2017 shows the range of weights and the number of birds in each weight category. The average of 168 is far lower than the 180-gram threshold necessary for a successful flight to the Arctic.

This season also challenged our understanding because it lies so far outside the norm. To be sure the cause of this dramatic scarcity of horseshoe crab eggs springs from the cold weather this May. We started with a good crab spawn in the first week of May, when water temperatures rose somewhat faster than normal, a consequence no doubt of one of the warmest winters on record. Then cold and wet weather dogged the Bayshore until the day of this post. Today, temperatures will rise no higher than 70 degrees Fahrenheit and the prospects for warmer weather are unlikely for the rest of the week. The cold air temperatures forced down the bay temperature in the second week and although it has gradually improved it is still low by normal standards.

The Delaware Bay water temperature as measured by the bour off Lewis Delaware. The Bay warmed early until the second week of May when cold weather chilled the Bay.

All of this led to generally diminished horseshoe crab eggs especially on the beaches, the mainstay of most stopovers of the past. This year crabs mostly spawned in the creek mouth and outer creeks shoals, mostly spurred to spawn by tidal waters warmed by the movement in and out of the small estuarine systems. Water moves in with the tide and out again to the creek mouths twice a day warming the shoals.

The Importance of Tidal Creek Mouths and Shoals

A shoal at the mouth of BayCove creek and the crab spawn on Reed creek.

The creeks also accumulate sand leaving them loose and perfect for crab spawning. Even in good years, egg densities in the creeks top all beaches, no matter where they occur. The sands of the shoals loosen by the waves of the Bay and release more buried eggs than those buried in the beaches, making more available to the birds. The creek mouths on the Cape May peninsula from Green Creek to Moores Creek saved the birds from an even worse fate this year and the best were those that benefited from the restoration of Reeds, Cooks, Kimbles and Pierce Point Beaches. As it happens a major portion of the Bay’s knots stayed in this area throughout the entire month but flying widely in search of pockets of good spawning in other places. This year Norbury’s in the south and Goshen in the north stood out, and extended the core stopover area.

Horseshoe crabs breeding at Reeds South shoal.

Spawning Starts Again

Then in the last three days all changed. The new moon tides, reaching around 8 feet for four nights in a row, spurred spawning despite the relatively cool water. Today, May 29, the crabs shifted into high gear.

It takes a lot of crabs breeding to bring eggs to the surface on the beaches, there must be enough breeding for one crab to dig up the eggs of another. For the first time, this occurred in the last few night and we finally saw green eggs on the sand. A welcoming sight for the birds, who could barely stand still and gobble up the fat producing eggs. With most of these Arctic nesting shorebirds remaining in the Bay and apparently feeding right into the night, they still might reach the fat gain finish line and only lose a few days reaching the Arctic. The next few days will tell.

Horseshoe crab eggs litter the surface of North Reeds Beach.

A close up of the same beach. The immense number of eggs on the surface of the beach is in part due to the number of crabs spawning and the wave action of the Bay.

Shorebirds and Gulls feeding near dark in the intertidal flats and creek shoals of Reeds, Cooks, Kimbles and Pierce Point Beaches.

Can they though? A good question and just one of the many that have challenged our team’s knowledge of this well-known stopover. With literally centuries of combined experience (many of our team, including this author, are long in the tooth as the Brits would say) we still kept guessing what would happen next throughout the season. Would the birds suffer mighty declines as a consequence of the generally diminished spawn of horseshoe crabs?  Or will they build weight in time to get to the Arctic in good condition? This is usually the central question.

Why Are There Fewer Knots?

An equally intriguing question, however, is why have red knot numbers in Delaware Bay declined this year? We estimate shorebird numbers in two ways, direct observation by aerial and ground counts and a statistically derived estimate based on the resighting of birds flagged with unique IDs. Our aerial and ground counts tell us how one year compares to another because we have been doing shorebirds counts by airplane, boat and on the ground since 1981. This year the number fell dramatically.

Guy Morrison, Christian Friis and Joe Smith survey shorebirds by airplane near Egg Island Point.

At the start of our project on Delaware Bay in 1986, we had nearly 100,000 knots on the Bay and nearly 1.5 million shorebirds of all species. The number of knots declined to around 15,000 in the mid-2000’s, then jumped to over 24,000 over the last four years. This year our best estimate is around 17,969, a 5,000-bird decline. Why did this happen?

One must always consider the possibility of a large group of birds dying. But this is not likely.

More likely, some portion of the knot flock came to the Bay, and on finding too few eggs or too much competition, moved on to better places. The ones moving on could have been the short distance migrants, those who spent their winter in Southeast US or the Caribbean. These birds travel a shorter distance and so have a longer time and lower energy needs than those that winter in South America. These long-distance migrants would have a very difficult time gaining weight on anything other than crab eggs (I explained this in a previous post). There are two reasons to believe the short distance birds moved on from the Bay this year.

The first is the discovery of birds banded in Delaware Bay this year and reported elsewhere. I reported on Mark Faherty’s Ebird report of a knot he saw in Cape Cod, that was flagged by the Delaware Bay Shorebird Team on May 16, 2017. The second line of evidence is the 1,300 birds seen by our team feeding on a 10-mile stretch of the Atlantic Coast marsh from Cape May to Stone Harbor. Play this out over the entire coast of New Jersey and other places with sand and marsh, like Cape Cod, and one could easily imagine 5,000 knots using other places.

About 200 knots feeding and roosting on the inter-tidal shoal of Hereford Inlet on the Atlantic coast.

But this reduction in population also suggests an explanation for the sudden rise in numbers found in 2013. Did the restoration of habitat on the Delaware Bay coast bring back knots that once used the Bay but stopped because of the lack of available eggs? In other words, did the increase in numbers seen in the Bay reflect a return of birds and not a population increase? This year’s loss may simply be a result of those returning birds, leaving once again.

Let’s hope so. At any rate, eggs are now available to all birds in the Bay and we should start seeing them leave for the Arctic. Let’s hope for that too.

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


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In Dangerous Territory on the Delaware Bay

Wednesday, May 24th, 2017

By Dr. Larry Niles, LJ Niles Associates, LLC

Four days ago, the shorebirds of Delaware Bay could look forward to a bright future. But in the last week their chances for survival and good production have diminished. In fact, they are as dismal as the cold drizzle pockmarking the murky water in front of our house on Reeds Beach.

The following two graphs tell the story. We captured red knots on May 12 and 16 that showed a normal, although not spectacular progression. Then we made a catch of knots on the 19th and again today on the 23rd, and in total they gained only 2 grams of fat per day. With an average weight of 144 grams at this late date and only 7 days to go before they must leave for the Arctic, their future looks bleak. If current conditions hold, the knots will suffer their worst year in 14 years. Turnstones fared no better gaining less than a gram per day on average.

The graph plots all the average weights of all the catches of red knot our team has made since 1997. The average weight of our catch on May 23 suggests trouble is brewing for these birds.

 

The graph plots all the average weights of all the catches of ruddy turnstones our team has made since 1997. The average weight of our catch on May 22 suggest trouble for both species.

So why this dismal report? Several factors are at work that were covered in my last post. The water temperature of the bay has only just exceeded the threshold for horseshoe crabs to start breeding in earnest. But the nights are cold and the water temperature remains cold. Last night was the first good crab spawn since the birds arrived and it was lackluster. Although there is some spawning in the creek mouth shoals and the lower beaches near Norburys Landing and Villas, our most productive beaches remain nearly devoid of crabs and crab eggs.

The second problem is still a mystery. At this stage only about half of the red knots have found their way into the bay. Weather patterns in the southern US could have been blocking migration for the last 5 days because adverse winds, poor visibility and rain impedes birds progress and could stop northward movement. The conditions have finally let up, so it possible a new cohort of birds might arrive any day. If so they will face a true food fight with many birds already here and desperate for eggs.

Laughing Gulls, Red Knots, Ruddy Turnstones, Sanderlings and Semipalmated Sandpipers struggle to find horseshoe crab eggs on the shoals of South Reeds Creek. Eggs are scarce because cool water temperatures prevent crab spawning.

However, it may not be the adverse weather but choice that is keeping the population down. Today we learned of a red knot banded on May 16 this year by our counterparts in Delaware that was resighted in Cape Cod by Mark Faherty, the senior scientist for Massachusetts Audubon in Cape Cod. In other words, red knots and other shorebirds are coming to the bay finding too little food or too much competition for the food now available and choose to move on. This is very possible for the short distance migrants because they arrive earlier and have less weight to gain before leaving for the Arctic. Knots wintering in Tierra del Fuego, arrive later and in much worse condition, often times lose muscle mass to get here. They cannot recover that loss and still gain an extra 80 grams on their normal diet of mussels and clams.

We tried to test this second possibility today (May 23) after our red knot catch this morning. Humphrey Sitters, Amanda Dey and I surveyed the intertidal mud flats of the Atlantic Coast from Cape May to Stone Harbor looking closely at the mussel beds. We know that every year red knots, especially short distance birds, use mussels and to some extent clams, rather than come to the bay and feast on horseshoe crab eggs – simply because they can. We found 1700 knots, so it possible even more are spread out further up and down the coast.

In the end, it may turn out to be both explanations. The short distance knots are using the Atlantic Coast and the long-distance birds have yet to arrive. One should remember that the knot is federally listed in both Canada and the US primarily because of the dramatic declines in the long-distance winters. There is still a small window for a successful outcome. The next few days will tell the full story.

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


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A Resilient Shoreline in Stone Harbor for Birds and People

Thursday, April 2nd, 2015
Conservation Partners Collaborate to Improve Beach Habitat for Birds and Provide Flood Protection for Stone Harbor Residents

By: Lindsay McNamara, Communications Coordinator

Oystercatchers © Dr. Larry Niles

Oystercatchers © Dr. Larry Niles

Beach nesting birds and New Jerseyans who live along the coast both depend on a resilient shoreline — and plenty of sand.

 

This season, thanks to a grant from the National Fish and Wildlife Foundation (through their Hurricane Sandy Coastal Resiliency Grants Program), a team led by New Jersey Audubon worked with Conserve Wildlife Foundation of New Jersey, The Wetlands Institute, New Jersey Division of Environmental Protection, and the US Fish and Wildlife Service to make the beach community of Stone Harbor Point more resilient for birds and people alike.

 

Conserve Wildlife Foundation of New Jersey collaborated with New Jersey Audubon to improve beach habitat for Piping Plovers (endangered in New Jersey), American Oystercatchers and the colonially nesting Least Terns and Black Skimmers. Sand from the southernmost tip of the point was moved to create three areas of higher elevation. The new landscape is expected to benefit Red Knots, Semipalmated Sandpipers, Sanderlings, Semipalmated Plovers, Black-bellied Plovers and others.

 

Stone Harbor, a small beach town along the New Jersey shoreline will see added coastal resiliency benefits and flood protection due to this innovative project that combined the needs for shorebirds with the needs for shore residents. The Stone Harbor project also included the construction of a wide berm of sand near the beachfront parking lot at the far south end of the town. This aspect of the projects aims to increase flood protection for the residents on the developed area of the island.

 

Learn more about this project on New Jersey Audubon’s blog and in the ShoreNewsToday.com article “Working for the Birds.”

 

The National Fish and Wildlife Foundation (NFWF) is a non-profit organization created by Congress to preserve and restore our nation’s native wildlife species and habitats. NFWF is one of the largest funders of wildlife conservation in the world. They fund science-based projects and community-driven solutions.

 

Lindsay McNamara is the Communications Coordinator for Conserve Wildlife Foundation of New Jersey.

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