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Posts Tagged ‘ruddy turnstone’

The Importance of water temperatures, windstorms and shoals on the Delaware Bay

Friday, May 19th, 2017

By Dr. Larry Niles, LJ Niles Associates LLC

As we begin our field work on Delaware Bay shorebirds, our 21st season, oddly enough we are once again faced with extraordinary circumstances. As usual, the birds, after various flight of up to 6 days of nonstop flying, arrive in emaciated conditions. For example, in one catch this week we caught several red knots at around 86 grams far lower than normal weight of 130 grams. Putting that into perspective, a woman of 145 pounds would tip the scale at 93 pounds while a male of 175 pounds at 113 pounds! In other words, these birds are desperate to feed on the only prey on which they can build weight fast, the eggs of Delaware Bay horseshoe crabs.

But the various impacts of climate change and destructive forces of sea level rise, storm surge and out of normal weather patterns can wreak havoc on the timing of the horseshoe crab spawn. It messes with the heating and cooling of the bay and when combined with the normal variation one expects in an estuarine system, it creates almost unpredictable consequences.

Adding more uncertainty to this mix is the ongoing harvest of crabs for bait and the irresponsible bleeding by international medical companies. Both kill hundreds of thousands of crabs every year while doing nothing to create new crabs. Their combined impact has put the brakes on any recovery of the population after they both nearly mortally wounded the Bay population in the 1990’s and early 2000’s. Higher numbers of crabs would overcome a lot of early season uncertainty; lower numbers exacerbate them.

And thus, the story of this early part of the shorebird stopover. It starts with the odd weather this April and May. Can everyone remember how warm the weather of this winter? The map below is a reminder that it was one of the warmest on record. The figure below that shows how the Bay’s water warmed early reaching the threshold temperature for horseshoe crab breeding by early May. We trapped sanderling in the first week and were surprised to see a truly great crab spawn on May 4. Thank God for that.

The bays water temperature as measured at the Lewis DE buoy, increased earlier than normal until the first week of May. By that time it reached the threshold for horseshoe crab spawning. But by the second week it plunged as a consequence of the cooler than normal weather.

By the second week of May and yesterday (May 16) temperatures plunged in horseshoe crab world. We generally consider water temperature of near 59 degrees necessary for crabs to spawn in great numbers. We reached 62 degrees on May 4, then it went down to 58 degrees, lingering there for five crucial days.

At the same time, we suffered brutal westerly winds. Wind from this direction gins up waves on Delaware Bay that crash against many of the important crab spawning beaches. Crabs don’t spawn in waves.

Westerly winds turn the Delaware Bay into a tumult of breaking waves because of its relative shallow depth. Horseshoe crabs won’t breed in breaking waves

And just as the first flush of shorebirds came to the Bay, over 5,000 red knots on the New Jersey side, all the spawning shut down. All tried desperately to find enough horseshoe crab eggs to regain lost weight and begin the process of doubling their body weight.

Fortunately, breaking waves and cold water will prevent crabs from spawning on the beaches but not in the intertidal creeks. One of the key features of the New Jersey bayshore are its abundant tidal creeks. Most drain only tidal watersheds, draining and filling marshes twice every day. Naturally they build sand shoals because sand moves around the Bay generally in a south to north direction along the Cape May peninsula. When sand encounters the currents of the creeks, it settles forming shoals.

A small creek just north of Dennis Creek on Delaware Bay. The tidal creek mostly drain tidal marsh, the daily ebb and flow warming the waters making crab spawning possible when the bay waters are too cold

These shoals support most shorebirds during these early days. This is so because the intertidal flow of water into the marsh and out again warms the water that flows over the shoals. The shoals themselves are practically paradise for breeding crabs because of the loosely consolidated and large grain sand. They breed with abandon laying eggs in the shifting sands that brings many of the eggs to the surface where shorebirds can prey upon them. And they do.

This diagram by Joe Smith shows how the creeks of Delaware Bay create superior spawning and shorebird foraging habitat. Sand movement on the Cape May section of the bay moves northward because of tidal currents. This moves sand from south to north. When the American Littoral Society and CWF placed sand on Pierces, Kimbles and Cooks beaches, some part moved northward to the adjacent beaches. Ultimately it ended up on south Reeds making it a great spawning site. But on the way the sand falls out of the current and settles on the creek shoals. These shoals are large grain sand, loosely consolidated, making them perfect for crab spawning. At the same time the shoals shift exposing eggs to the sea, thus making them available to the birds. This is why the shoals are among the most important habitat on the bay.

This is what happens in the early days of this season. It was nip and tuck for most of the scientists, not knowing if the shoal resources would hold up to an ever-growing number of shorebirds arriving in desperate condition.

But today (May 19) we enjoyed warmth with the promise of the season back on track.

In the last 5 days, we were able capture enough knots, turnstones and sanderlings to track conditions and add new flags to the population for a later determination of population size. Despite adversity, so far so good. The data for each species is below.

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


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Shorebird Expedition Brazil: Going to the heart of the mangroves

Wednesday, February 15th, 2017

Hundreds of red knots found to cap long day’s journey

By Larry Niles, LJ Niles Associates LLC

It took us long into the night to reach our next port.  We went from the relatively populated area of Braganza to the dark heart of this coastal region of Viseu. In three trucks, we caravanned through a maze of remnant tropical rainforests, cattle pastures, and impenetrable second-growth woodlands. Along the rain-slicked, red clay road, small and desperate looking towns popped out of nowhere always looking like the past was a better day. The road cut through countless mangrove forests that define this region.  We reached Viseu too late to do anything but find a place to stay the night.

A bridge across the many rivers from Braganca to Visiu, Brazil. Photo by Christophe Buiden.

By noon the next day, we boarded a Lancha boat named Garota Viseu (Viseu Girl). Local shipwrights craft these two-decker boats of about 50 feet in length, primarily to carry cargo and people from port to port.  Today it will carry us into one of the most remote estuaries in the 250-mile coastline of this enormous mangrove and beach landscape.  Our captain, 78-year-old Benedicto, with one crew navigated the coffee- colored Gurupi, a long river that cuts deep into the tropical coastline.

A nearly completed boat in a ship yard in Viseu.

Bene took his craft down the Gurupi within sight of the wind-tossed Atlantic Ocean.  The trade winds blow constantly here, almost always at near gale levels.  But then he turned into a small channel directly into the steamy mangrove forest.  At first the path was wide, lined with a dense tangle of mangrove on either side.  Whimbrels, scarlet ibis, semi-palmated sandpipers clung to tangles of roots as the high tide flooded the soft mud.

Captain Benedicto piloting his Lacho boat, the Garota Viseu.

Then he took the boat in a channel so narrow, the crew had to duck the whipsaw of mangrove branches.  We slowly snaked our way through a tunnel of green until we reached another wide channel.  Within a few minutes, we entered another narrow channel ultimately reaching the next bay.  Here we felt the full force of the stiff winds and deep rolling swell of the Atlantic.  An hour later we weighed anchor at the small community of Apiu Salvadore.

The Garota Viseu weaves its way through the narrow mangrove passage. Stephanie Feigin, Danille Paluto, Christophe Buiden and Yann Rochepault watch from the top deck of the boat.

 

 

Few people from the outside world come to this community of about 50 ramshackle huts and cabins and about 150 people. As the boat neared the shore with most of the team standing on the roof of the boat, scattered groups of the town’s people stood on the sandy bluffs overlooking the harbor as though we just landed from space.  Ultimately, we found them welcoming but wary.  Little good comes from the outside to these communities.

 

 

Over the next two days, we plied our craft of field biology. We needed to find small boats to take teams to the various shorebird habitats previously determined on our maps. Local craftsmen build these boats. Running about 20 feet in length, they use 10 to 20 horse power engines meant for something like a lawn tractor. Instead of driving a blade, the craftsmen power a long shaft that ends in a 8-inch propeller. The skipper can lift the engine and propeller according to the water’s depth. They suited our needs perfectly.

 

We fielded five teams in three in boats while Mandy, David Santos, Carmem and I surveyed Lombo Branco Island, about two miles from the Apiu Salvador. The sea shapes this island into a crescent, the inside protected from the restless waves.  Nestled within, one could see in miniature, the whole ecological system that creates resources for shorebirds.

 

At the heart of the island grows a small and stunted mangrove forest and an apicum, or wetland that only floods during lunar tides or spring tides. These are the highest of the monthly cycle of tides but only occur on the full and new moon. Every day the tide moves in and out of this small system. Twice a month the tide floods the apicum for several days at a time.

We arrived on the day of a waxing moon, near full. The very high-high tides reached well within the small drainage flooding habitats that have not been flooded in a few weeks. Shorebirds carpeted the wet mud, searching for all the invertebrate life that flourishes in this habitat. But the productivity only starts there. Here the tidal flow is gentle because the island shields it from the wind tossed Atlantic from all sides except the leeward quarter of the island. This gentle tidal flow flushes sediments from the mangrove swamp, the nutrients of the apicum and the normal productivity of a sediment-rich sandy substrate, forming the base layer of a productive food chain that nurtures small clams and other invertebrate – all prey for shorebirds.

 

We found whimbrels, semi-palmated sandpipers, ruddy turnstones, short-billed dowitchers, black belly plovers, willets, semi-palmated plovers, sanderlings and collared plovers.  In the lower reaches, we found 337 knots, a glorious find that will help our mapping model enormously.

Red knots, sanderlings, short billed dowitchers and other shorebird forage in the inter-tidal estuary of Morro Branco.

The following day we surveyed a second island, Coroa Criminosa. Why the sinister name we cannot say, but it supported a very similar esturary giving us another successful day. When the tide went out the small island of about 6 kilometers grew to over 20 kilometers. Intertidal sand flats spread out of sight in nearly all directions.

 

 

We left the island that night and arrived in Viseu just before dark. Once again we suffered the sway of the Atlantic. After weaving our way back through the mangrove and up the Gurupi River, we landed too late to go on.  We were thankful for the modest rooms with showers, a good meal and beer!

 


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


Shorebird Expedition Brazil: Conducting a scientific investigation in a tropical wilderness

Thursday, February 9th, 2017

By Larry Niles, LJ Niles Associates LLC

It’s hard to imagine the difficulties of people living here at Latitude 37 Degrees North when arriving at the equator in northern Brazil. It challenges even the hardiest of biologists. However, after three days our team has not only acclimated but we accomplished surveys in two separate estuaries.

 

Ruddy turnstone multiyear flight recorded by a geolocator caught in Maranhoa, Brazil.

 

Low tide was cut short on our first day in the field, while high tide persisted longer than we expected which challenged our surveying since it must take place when birds forage. Shorebirds typically forage until 1 to 2 hours before high tide and start again 1 to 2 hours after high tide, usually resting and digesting the food consumed at the lower tides. Because we intend to understand the foraging habitats of shorebirds in the wintering area, we must focus on the lower tides. This is always difficult due to logistical issues such as renting boats, equipment failures, and long distance from the ports present an array of complications. Still, we were able to go out in the field and collect some data.

 

The next day we did marginally better, each team member faced different problems. Our boat engine failed and we had to paddle back to port, another boat took so long to get to the shoal we intended to survey that it had already been covered by the tide.  But this is the nature of field work anywhere.

 

Yann and Christophe paddle our boat back to port after the engine failed.

 

No matter the complication, it is important to stick to our rigid protocols.  Our goal is to determine the best places for shorebirds in this area. We must work with the shorebird’s behavior because each tidal stage creates different value.  In a wild place such as this, they will choose to roost as close to the foraging areas as possible. In fact most will just roost then feed as the tide recedes then feed as the tide rises and then roost again.  So locating the feeding areas will usually indicate the roosting areas.

 

But things can go awry. In human dominate habitats like New Jersey, birds find it hard to roost near foraging areas. Most often the high tide forces them into people jogging, dog walking or enjoying flushing shorebirds.  So the shorebirds must leave, unnecessarily burning valuable fuel and suffering greater danger from avian predators.

 

The night-time roost creates the real threat here in Brazil and everywhere. At night many dangers lurk.  Ground predators, such as owls, feral cats, raccoons, and even people will take advantage of any unwary or sickened bird.  It is worse when birds are forced to use areas that are less secure than others. This can happen naturally at spring tides, for example, when the very highest high tides force them closer to the dangers lurking in the dunes or mangrove forests.  In places like Hereford, New Jersey, people often force birds to use more dangerous areas.

 

Larry Niles surveying.

 

So our goal here is to map all the areas of importance – foraging, day-time roosts and night-time roosts.  But we hope to do it with remote sensing; satellite maps that are trained by a mathematical model, that are, in turn, trained by our field data.  We count birds, photograph the surrounding habitats, precisely locate the sites, and even look at the substrate.  Is it mud, sand, muddy sand, sandy mud and so on?

 

Doing this in New Jersey is difficult.  Doing it in the northern coast of Brazil presents untold challenges.  One cannot easily access the coast here.  We have to rent boats to take us out to the birds, conduct surveys then get back before dark.  Sometimes we go out for days and stay in remote fishing villages, sometimes with only a floor to sleep and no facilities or power. Imagine unrelenting heat, mosquitoes, persistent blowing sand, copious sweat, and trying to conduct a scientific investigation. That would be demanding in any environment.

 

So this is the challenge of our crew – and they do it aplomb!  Last year one of the boats sank in 55 feet of water 8 miles out to sea. We all made it to land safely but we lost much of our equipment. The day after was grim, wondering if we should we go on or go home?  Without hesitation, not only did the crew go on to complete the survey but we ended up capturing twenty-two geolocators from ruddy turnstones tagged two years earlier. A good crew is hard to put together and stay productive in these conditions. A good spirit is the most important thing.

 

Our team chooses areas for the next day’s surveys. Beer is essential!

 

So we completed two days of surveys at the western end of our 150 miles long study area. Today we prepare for three days out to a remote area, accessible by boat only.  As I write, the team prepares for food, water and all the necessities of spending three days with minimum comfort.  We hope to camp in a fishing village, maybe a house, but we won’t know until we get there. We must prepare for all possibilities.

 

Our understanding of the inner workings of the Brazilian Extractavista reserve system grows every day. This system I believe holds great hope for us in the United States because it serves both the wildlife and fish and the people living in the landscape.  Pretend, for example, on Delaware Bay, the rural towns and the residents get first crack at the sustainable management of resources, not the companies exploiting them without regard to the future, as it is now. Instead of few people earning a good living off Delaware Bay resources, many would. Rural American would be transformed. This is what ICMBio hopes to achieve in this much poorer area.

 

Two members of our team are managers of the seven reserves in Para, our study site. They told us, for example, ICMBio (Chico Mendes institute), the federal agency in charge of the extractive reserves, pays a subsidy for local fishermen in exchange for helping manage the fishery resources. But the subsidy is limited to existing residents, not people within new reserves because of the new conservative government. One can see right away the challenges of two people managing seven reserves covering a coastline the size of New Jersey. Budget cuts have taken away all equipment funds. They must even clean their own offices as most nonessential staff has been cut under the new conservative government, a government accused of unfairly deposing the most popular liberal party.

 

This should resonate in the United States because it could be coming soon to a wildlife reserve near you.

 

Wintering knots in roost.


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


 

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