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A Shorebird’s Paradise

Thursday, May 26th, 2016
One in a Series of Updates on the 20th Year of the Delaware Bay Shorebird Project

by Dr. Larry Niles, LJ Niles Associates LLC

Photo by Jan van der Kam.

Photo by Jan van der Kam.

We conducted our first bay-wide count of shorebirds on Delaware Bay and the results suggest we are rapidly approaching the peak number of shorebirds. Last year, we counted 24,700 knots and 16,000 ruddy turnstones. This year’s counts are lower because it’s earlier, but we are still over 20,000 knots and 16,000 turnstones, and 10,000 sanderlings that have stopped over in the bay. These promising results are preliminary, but it seems we are getting close to our peak population of red knots and at the peak of the other two species – if populations are similar to last year.

This year’s aerial counts were conducted by Guy Morrison and Christian Fries, both of Environment Canada.

This year’s aerial counts were conducted by Guy Morrison and Christian Fries, both of Environment Canada.

Bird condition also looks promising. Our catches show average weight increases for red knot compared to past years, which is good news given the very spotty horseshoe crab spawn. Ruddy turnstone average weights have increased considerably, the best in the twenty years we have been trapping (see the graph below). The distribution of these weights reveal more.

This graph shows the average weights of all ruddy turnstone catches made from 1997 to 2016. 2016 is represented by big squares and shows a very good increase in weights.

This graph shows the average weights of all ruddy turnstone catches made from 1997 to 2016. 2016 is represented by big squares and shows a very good increase in weights.

If we sample the same bird population with our cannon net catches, one would expect increasing average weights but similar distribution of weights – the same proportion of different weight birds, all getting higher. If a new group of birds arrives in the area, then one would see a new distribution of weights, only lower than the group that has been in the area longer. This can be seen in the historgram for ruddy turnstones below. The historgram supports our assumption that a new group of turnstones has arrived in the bay and are busy gaining weight. Based on our last catch, the distribution of knot weights shows no new arrivals, however the aerial survey and ground counts done after the catch point to a new group yet to be sampled. To our team of biologists this data is food for hungry minds. Within a few days, all will be revealed.

This histogram shows the number of red knots in each weight category in our catch made on May 21. See text for more explanation.

This histogram shows the number of red knots in each weight category in our catch made on May 21. See text for more explanation.

The actual distribution of the birds in the count tells another important story – the importance of the beaches and creeks between Reeds Beach and Pierce’s Point. This 3-mile section of Delaware Bay accounted for more than half of the entire population of red knots on the bay and outsized portions of the other species. This has been consistent through this season and over the last three years – ever since Conserve Wildlife Foundation (CWF) and American Littoral Society (ALS) restored the four beaches with new sand.

map of reeds to pierces cove

The restoration of these beaches avoided a potential disaster caused by Hurricane Sandy, which not only destroyed seventy percent of all the suitable horseshoe crab habitat on the New Jersey side of Delaware Bay, but it did much more. South Reeds Beach tells the story.

 

After the hurricane ripped through the area and pounded Reeds Beach with punishing westerly winds, most of the sand had been pushed off the beach and onto the marsh behind it. This unveiled a long standing and nearly impervious layer of rubble, remnants of long abandoned houses, bulkheads and the access road connecting them. We had no idea this laid beneath the sand of Reeds Beach South, but it explained why it never had good crab egg densities. Crabs couldn’t burrow deep enough to lay eggs.

restored beaches

The CWF and ALS restoration teams with funding from the United States Fish and Wildlife Service (USFWS), National Fish and Wildlife Foundation (NFWF), the Geraldine R. Dodge Foundation and Community Foundation of New Jersey, along with other groups, removed the rubble and laid down a beautiful sandy beach.  Every year since, horseshoe crab egg densities were among the highest in the bay.  This, of course, attracted higher than average shorebird numbers which greedily consumed the newly available trove of eggs. Similar work was done at Cooks, Kimbles and Pierce’s beaches.

 

However, the restoration work did even more. Sand naturally erodes from these beaches just as it does on the Atlantic Coast beaches. The sand lost at Stone Harbor and Avalon beaches, for example, ends up in Hereford Inlet. The same happens on Delaware Bay beaches and the eroding sand flows into the the nearby creeks forming beautiful crab spawning shoals. I described their importance in the Reeds – Pierce’s Cove in the previous blog. These creek shoals represent the best habitat in the bay, because they are loose sand, create small inner protected areas loved by spawning crabs and are washed by warm water flowing out from the small intertidal water drainages. Early season spawning almost always occurs in or near creek mouth shoals. Thus, even sand lost from restored Delaware Bay beaches goes to a good end.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

One more characteristic, perhaps the most important feature, is that all these beaches, creeks and their shoals together create a small and very important landscape within the overall Delaware Bay landscape. The overall warming creates the best early season habitat for crabs and shorebirds and the continued volume of spawning maintains the value throughout the season. We now have over 10,000 knots on these beaches and thousands of other shorebirds.

 

All of these important natural features are greatly strengthened by the New Jersey Division of Fish and Wildlife’s restrictions that keep people from disturbing the birds. Without them, visitors, even those with good intentions, may disturb the birds from feeding.  The restrictions are implemented without conflict by a very cheery and passionate group of volunteer stewards who explain the importance of letting the birds take advantage of good habitat. Ironically, the Reeds to Pierce Cove still attracts the most people in the bay because they can easily see the birds from access areas provided at each of five road ends and the Bidwells Creek jetty.

 

All in all, it’s a shorebird’s – and shorebird lover’s – paradise. But soon it may be a paradise lost.

 

This year, state and federal agencies permitted thousands of structural aquaculture racks to sprawl over this wonderful shorebird habitat. If all goes according to their plan, soon ATV’s will be rolling all over the intertidal area, disregarding their long-term impact. Welded rebar racks will stop some a portion of the crabs from reaching the beaches, and more importantly impair their return. More and more crabs will fail to breed or die as gulls tear apart crabs stranded on the intertidal shore. Like much of New Jersey, this beautiful cove has the potential to be degraded by runaway commercial exploitation.

aquaculture and birds

This photo of about 4000 red knots and turnstones was taken at low tide in an area the federal and state agencies have declared as not useful to the birds, about 300 meters from the beach. It is also the area now be filled by the sprawling oyster aquaculture. Looking close you can see the first of the racks in the background on a lease owned by family of staff of Rutgers Extension, the primary advocates of the expansion. – Dr. Larry Niles

There are ways to expand aquaculture without destroying shorebird habitat. This is not one.

 

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

 

New Jersey’s Hidden Coast

Tuesday, May 24th, 2016
Discover New Jersey’s Hidden Coast – the Delaware Bayshore

by Lindsay McNamara, Communications Manager


Making your plans for Memorial Day Weekend at the Jersey Shore? Discover New Jersey’s “other” coastline, a Hidden Coast, the Delaware Bayshore.

 

A new episode of our video series “New Jersey’s Hidden Coast” will air every two weeks throughout the summer! Catch a glimpse of the bay, the horseshoe crab at the center of the bay’s system, and the incredible relationship between horseshoe crabs and migratory birds, like the red knot. We will reveal the real value of horseshoe crabs, the challenges to the ecosystem, and the potential for a thriving regional economy along the Bayshore. We will show Hurricane Sandy as a catalyst for decisive action and the work being done to rebuild the area for both people and wildlife.

 

Over the next several weeks, we will explore the use of “living shorelines” instead of bulkheads and the central importance of marshes to the marine ecosystem. We will discover the on-the-ground, grassroots efforts of the community to build oyster reefs alongside veterans. And we will examine the future of the Bay and the work that needs to be done to preserve our conservation successes thus far.

 

Discover Delaware Bay:

 

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

Creek Mouth Shoals Provide Key Habitat During a Cold May

Monday, May 23rd, 2016
One of a Series of Updates on the 20th Year of the Delaware Bay Shorebird Project

by Dr. Larry Niles, LJ Niles Associates LLC

In spite of the very spotty horseshoe crab spawn, the shorebirds on Delaware Bay seem to be gaining weight on schedule. Below you will find a graph composed of the average weights of all the red knots by our team for the last 20 years. The curve is the result of combining all the data we collected and shows the sweet spot for most knots. As they arrive, they take time to gain weight but after about 5 days they start gaining weight rapidly. After the 26th or so, birds start reaching the critical weights necessary to safely reach the Arctic breeding grounds. One can see the curve deep at the end of the month because fat birds fly off leaving the less fat behind. In general, weights above the line are good, below the line not good. The large squares on the graph are the average weight of this year. So far, so good.

Average Red knot weights from catches made in 1997 to 2016. The most recent are the big squares. So far average weights are following normal pattern of weight gain.

Average Red knot weights from catches made in 1997 to 2016. The most recent are the big squares. So far average weights are following normal pattern of weight gain.

Cannon net firing over red knots on Delaware Bay

Cannon net firing over red knots on Delaware Bay

This is a bit of a surprise for the team. The weather here on Delaware Bay is wet and cold. The water temperature struggles to lift above 59 degrees, the temperature necessary for a crab to spawn on Delaware Bay. So far, the temperature has been below 59 degrees more than above. We had good spawns in the last few days, but only in key places.

Water temperature at the mouth of Delaware Bay.

Water temperature at the mouth of Delaware Bay.

A key place for horseshoe crab spawn happens to be the mouths of small creeks. The New Jersey side of Delaware Bay is blessed with many small intertidal creeks, most draining only marsh or small inland watersheds. Some of these creeks have names, Goshen Creek, West Creek, Nantuxent Creek, but many do not. Almost all have shoals at their mouth with the bay because bay currents, tidal flow and wind driven waves act against each other to settle sand coming from adjacent beaches or from inside the creek drainage. Much of the sand lost from our restored beaches settles into these shoals. For horseshoe crabs, these shoals are sweet places.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

A sandy shoal at the mouth of the nameless creek between Reeds and Cooks Beach. At the time of this picture, over 3,000 knots and 1,000 ruddy turnstones were using the shoal and the inner sandy beach behind the shoal. Photo by Stephanie Feigin.

Red Knots in flight on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots in flight on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Red Knots on Cooks Shoal. Photo by Stephanie Feigin.

Usually, the shoals lie just under the high tide line and are composed of large grain sand, the optimal conditions for a good crab spawn. However, the most important characteristic and key to this unusually cold May, is the warming water flowing out from the marsh drainages. On a flooding tide, colder warmer flows into the vast marshes of the Delaware Bay. This warms the water. On an ebbing tide, it flows out the creek and over the shoals, making them slightly warmer and more conducive to inducing crabs to spawn. Even on these cold days, they literally climb over themselves to breed on the shoals. The shoals also protect the inner mouths of the creeks thus making the sandy shores at the mouth of the creek a crab spawning heaven.

Breeding horseshoe crabs. Photo by Jan van der Kam.

Breeding horseshoe crabs. Photo by Jan van der Kam.

However, as it seems usual with this blog, there is a growing concern. Right now, most of the red knot population on the bay is feeding on these shoals along with thousands of other species, but only half have arrived from southern wintering areas. We now have about 12,000 red knots on the bay and in a day or two we should find another 12,000 falling from the sky. Will there be enough eggs? Will the water temperature finally reach normal levels? These are the important question for the next few days.

 

Learn More:

 

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

Beachnester Buzz: First American Oystercatcher Chicks of the Season Hatch

Monday, May 23rd, 2016
New, weekly updates from New Jersey’s beach nesting bird project team

by Todd Pover, Beach Nesting Bird Project Manager

American Oystercatcher Chick

American oystercatcher Chick

It has been a busy week on the beach nesting bird project! We had our first least tern nests of the season, as the brief spell of warmer weather (finally) made for a burst of breeding activity. The first American oystercatcher nests hatched, so we have chicks on the beach now, as well.

Least Tern Nest

Least Tern Nest

And there was a big spike in new piping plover nests all along the coast, so we were busy erecting “predator exclosures” to protect the eggs from predators, such as crows, cats, gulls, and foxes. While they are not effective or viable to use on every nest, these wire cage structures are one of our best management techniques to increase hatch success by deterring predators.

Piping Plover Exclosure

Piping Plover Exclosure

 

This week we will be even busier, as we make a mad scramble to protect the nests and colonies before the crowds of beachgoers arrive for the Memorial Day weekend!

 

Learn More:

 

Todd Pover is the Beach Nesting Bird Project Manager for Conserve Wildlife Foundation of New Jersey.

Cold Water Stops Horseshoe Crab Spawning along Delaware Bay

Saturday, May 21st, 2016
One of a Series of Updates on the 20th Year of the Delaware Bay Shorebird Project

By: Dr. Larry Niles, LJ Niles Associates LLC

Shorebirds and no horseshoe crabs along the Bay.

Shorebirds and no horseshoe crabs along the Bay.

It’s well known that the Delaware Bay shorebird stopover depends on horseshoe crabs, but few know that Delaware Bay is a near perfect horseshoe crab habitat.

 

There are many places on the eastern seaboard where horseshoe crabs breed. Most are too small to provide sustenance for energy-starved shorebirds. Places like Cape Romain Refuge in South Carolina have enough horseshoe crabs so that one breeding female unearths eggs of another and thus lays out a tidy meal for shorebirds. But the areas are small and at this time unimportant to the population of shorebirds. Most of the others are too small to have eggs reach the surface. Its only in Delaware Bay where crab numbers reach into the millions and spawn in such great numbers that they spread like a carpet over nearly all beaches from Gandy’s Beach to Villas, approximately 20 miles of spawning habitat. The number of eggs and ultimately hatched young reach staggering numbers.

Horseshoe crabs breeding at night.

Horseshoe crabs breeding at night.

The huge population of horseshoe crabs on the bay is no accident. The bay almost seems built to suit the crabs. Crabs need beaches with large and deep sand flats, allowing just enough water to sufficiently oxygenate the eggs without drowning them.  They need the sea floor to gently rise into breeding beaches, allowing easy access. While breeding, crabs have to eat small bivalves, which they find in abundance in the bay’s extensive intertidal and subtidal flats.

Horseshoe crab eggs.

Horseshoe crab eggs.

The most important aspect of the bay is its quickly warming waters in the spring. On Delaware Bay, horseshoe crabs don’t breed until waters reach 59 degrees. You won’t see this temperature on the Atlantic Coast until June. Not so on Delaware Bay!  Although the bay has deeper water, mostly in sloughs that snake under the surface out to its mouth at Cape May, most of the water is relatively shallow  usually less than 18 feet. That may sound deep, but keep in mind the Chesapeake has 100 feet water for most of its length and deeper water throughout. The shallow water of Delaware Bay allows it to heat up soon after the air temperature rises.

 

Unfortunately, it also cools down quickly and because of this the crab spawn has stopped. The bay’s water temperature went up dramatically in late March and April, so much so that we worried it might reach the critical 59 degree threshold in April long before the birds arrived in May. But then the warm weather stopped and the bay temperature dipped than rose, several times in fact. By early May, it had gotten just above the threshold, heating up to about 61 degrees at the Cape Henlopen marine buoy. We hoped for the best. Crabs started to breed in good numbers on a few beaches, like Reeds Beach, but were thin elsewhere. We had about 20,000 shorebird relying on the spawn and the eggs that were brought to the surface.

chart-13

Than the bay cooled down again. A nasty western wind and cold front enveloped our area over the weekend and the cool weather followed. By Monday, the temperature went down again and the crab spawn stopped. This is bad.

 

When the spawn stopped the birds hovered up the remaining eggs in a few days. Then they started wandering to find eggs in odd places, under houses, along bulkheads. Some even went to areas like the oyster aquaculture racks to find eggs to the delight of the people trying to expand aquaculture. But what they saw was desperation.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Worse the Black Back and Herring Gull that feed on eggs and overturned crabs couldn’t find eggs and started eating shorebirds. By the end of Thursday (May 19) we found 8 dead red knots. These gulls can swallow small sanderling and semipalmated sandpipers like gum drops, so we really don’t know how many shorebirds died.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Herring gull hunting red knot, Cooks Beach, New Jersey. Photo by Jack Mace.

Relief might be in sight though. Thursday, Friday and today will be warmer. The bay’s temperature is back up over 60 degrees. Thursday night we had a fairly good spawn. Hopefully we will be back in business soon.

 

Learn More:

 

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

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