A new study investigates the habitat preferences of endangered Red Knots in their vast, remote Arctic breeding range. Credit: M. Peck for Phys.org
by The American Ornithological Society, via Phys.org
Rutgers University’s Richard Lathrop, Conserve Wildlife Foundation of New Jersey’s Larry Niles, and their colleagues attached radio tags to 365 knots captured while migrating through Delaware Bay in 1999-2006. To learn where and in what sort of habitat the tagged birds nested, they then conducted surveys via small airplane across the south and central Canadian Arctic, a vast study area spanning from Victoria Island in the west to Baffin Island in the east.
The study shows that there are more than 74,000 square kilometers of suitable rufa Red Knot habitat across their Central Arctic breeding range—enough space for at least that many breeding pairs, assuming one square kilometer of territory per nest.
With the stopover period winding down, we can say the red knot and other shorebird species left the bay in better condition than the disastrous condition of last year. So what does it mean?
First, the last four years have been a sort of ecological roulette for the birds. Horseshoe crab numbers remained at only 1/3 the potential population possible on Delaware Bay leaving birds at the mercy of good conditions to get enough eggs. Last year, water temperatures stayed low during the mid-May depressing the spawn and the density of eggs. Although the average was 8000-eggs/square meter, there were less than 2000 eggs/ meters square in the month of May. Continue reading “Birds in better condition than last year but still face an ecological roulette”
The Press of Atlantic City covered the troubling findings of Conserve Wildlife Foundation’s recent expedition to Tierra del Fuego in Chile to survey wintering red knots.
The numbers of red knots – an endangered migratory shorebird that spends every May along New Jersey’s Delaware Bay coast feasting on horseshoe crab eggs – declined by more than 20 percent between the team’s counts last year and this year.
This recent story highlights the threats facing red knots and the horseshoe crabs they depend on, as well as Conserve Wildlife Foundation’s role in protecting the species.
NewsWorks ran a feature story on red knots and the incredible team of international volunteers who make Conserve Wildlife Foundation’s past two decades of scientific surveys possible.
I am reviewing a new paper by Sjoerd Duijns, a student working on the benefits of being a fat shorebird. Still, a draft, the paper analyses data from radio-tagged red knots leaving the Bay in good condition (i.e. fat) and finds they may leave later from Delaware Bay than lighter birds but arrive earlier in the breeding grounds because they can pick the best time to leave. They are also more likely to breed successfully and survive the Arctic breeding season to the following fall. In other words, being a fat knot on Delaware Bay makes life good.
So, in light of this new information, how did the red knots and other shorebirds fare in this year’s Delaware Bay Stopover? One must not be firm, with so many unknowns, but here’s a working biologist’s best guess.
By all accounts it was one of the worst years in recent memory, but with a twist that offers a glimmer of hope.
First, the Bay’s water reflected an unusually cool May and never really warmed to the levels necessary for a really good horseshoe crab spawn until the very end. This caused odd occurrences of crab spawning. For example, crabs bred in greater densities at the southern beaches this year, more than in previous years. The spawn at Norburys Landing, just south of the commercial oyster aquaculture development zone (ADZ), was one of the best this year, and knots and other shorebirds used the area in great number. One can only guess the water temperatures warmed over the wide inter-tidal flats provided just enough to elicit spawning. The same process was true of all the creeks on the Bay.
Laughing Gulls and shorebirds feast on horseshoe crab eggs at Norbury’s Landing just south of the Aquaculture Development Zone. (below)The southern portion of the bay was much more important this year because waters warmed faster on the large inter tidal shelf of this portion of the bay.
Second, the knot numbers never really climbed to the levels of the last three years. I’m guessing this was illusory, a consequence of the count being done on two days at the peak. It’s likely many more birds came to the Bay and seeing many birds for too few eggs, left for better resources elsewhere. Those that left were probably short distance winterers – those from relatively close in Florida and other nearby areas. The Bay’s horseshoe crab eggs would help them too, but they can get by on Atlantic Coast clams and mussels. The long-distance birds are the ones that need the Bay’s resources.
Third, when finally, the spawn got underway, a freak concurrence of wind and tide killed many thousands of crabs, potentially damaging the population and very likely ending any possibility of a really great spawn. The cobblestone road of crabs on the water’s edge. We saw none of that this year. Not once.
The upper graph compares predicted high tides ( in blue) with the actual high tide (in Red). On the night of 26 May. This occurred during the lunar spring tide, the highest in May. Finally, a brief burst of NW wind pushed the abnormally high tide into waves breaking across the beach berm, carrying with it tens of thousands of horseshoe crabs.In a freak concurrence of wind and tide, waves pushed horseshoe crab over the beach into the marsh by the thousands.
Grim results, but here’s the twist. In good years, knots leave near the 27th of May. One day they jam the beach gobbling up eggs, the next day there gone. In bad years, they linger. In 2003, we caught birds on the June 10th. There’s a cost to this of course, in lower survival and failing production. This year was a new in between. By the time of departure on May 27th, less than a quarter of the knots were prepared to leave. But they hung on until the 30th, blessed with a new flush of horseshoe crab eggs created by a middling spawn and a northwesterly wind churning up the beaches and exposing deeply buried eggs. Did the birds gain enough weight?
It’s hard to say, our last catch of just 33 knots suggests they might have, but an end-of-the-season catch makes a poor assessment. Once birds start leaving, the ones behind could be the light birds not ready to leave, or the heavy birds waiting for better weather. We won’t really know until the fall counts in the southbound stopover or the winter count in Tierra del Fuego.
This, our 21st season of intense research and conservation on Delaware Bay by all accounts will be like no other. Throughout all of it, the team of scientists and volunteers remained inspired, energetic and resourceful. In this one month, we conducted more scientific investigation and conservation than most projects do in an entire year. Whatever the outcome of this year’s stopover season, our team can look hopefully to the north and know that all that could be done for the birds was done.
Those of us that were paid for our time sincerely thank those who volunteered their time including; the stewards that manned the closed beaches helping hundreds of people understand why closures were needed; the volunteers in the banding team who endured long hours of preparing equipment, making bands, sewing nets and keeping cages and of course counting, catching and processing birds; the volunteers who doggedly pursue opportunities to resight flagged birds to estimate numbers and yearly survival; the volunteers that provided meals every single night, a welcome relief from a hard day’s work; and finally, the volunteers that went out all over the Bay to save horseshoe crabs in weather both good and bad. We all did our best. God help the birds and horseshoe crabs.
Our banding team on a catch at South Reeds.
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
Higher than usual tides last week caused an extraordinary stranding event of Horseshoe crabs all along the Delaware Bay. From Fortesque Cumberland County to beaches in Cape May County horseshoe crabs were washed up into the marshes, tidal flats, roads and other areas where they were unable to get back out to the water. ReTurn the Favor coordinators jumped into action and after an initial survey of the strandings organized rescues at the various beaches. On Saturday a team met at Pierce’s Point at sunset so as not to disturb feeding shorebirds. The group was made up of ReTurn the Favor coordinators from the Wetlands Institute and volunteers including CWF staff. The group was able to move ~3,000 crabs back to the water in a few hours. Over the next few days, rescue efforts continued at Pierce’s Point and other beaches. Allison Anholt from the Wetlands Institute reports that 7,900 crabs total were rescued at Pierce’s Point. Thousands of more crabs were rescued at other beaches over the weekend, due to the dedication and help from the various groups and wonderful volunteers involved.
Efforts like this show that caring, dedicated people can make a difference. Thanks to all involved!
Horseshoe Crabs stranded in marsh behind Pierce’s Point beach 5/27/17
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.
Over the last few days of our expedition, we left the state of Para and flew to Sao Luis in the adjacent state of Maranhao. There we began the next phase of our work, trapping red knots, ruddy turnstones and other species, as we have done since 2014.
But prior to leaving Para, while we stayed in the village of Apiu Salvatore, the fishermen asked to meet with Max. He hadn’t planned it, so at first, the reason was unknown. The fishermen of the village knew Max represented ICMBio, and that Apiu Salvatore fell within Resex Gurupi-Piria, one of the Brazilian agency’s many extractive or Resex reserves. As I described in the previous post, ICMBio conserves natural resources in each reserve for the benefit of traditional communities, such as this one. So Max had a good idea what the community had on their mind.
David and Danielle prepare for the meeting with the fishermen of Apiu Salvadori.
We entered the large open meeting space under a thatch roof with a good breeze cooled by a sudden evening downpour. The association leader, Antonio, got down to business. He explained the problem of immense ships lurking offshore, spreading giant purse seines or immense lines of baited hooks, and stealing all the fish. It threatened their own lives, not only their livelihoods but their very existence. One could see very clearly how vital fish were to these fishermen. The community consumed virtually no goods; most of their daily needs came from the sea or their backyards. Chickens, pigs, even lambs filled backyards. Fruit like mangos and avocados literally fell from the trees. I saw no washing machines, microwaves, coffeemakers, or nearly any of the appliances that litter a typical U.S. kitchen.
There was one modern device found in every hut and cabin, no matter how small or dilapidated. All had TVs. How, I imagine, can they fit in this primitive world while gapping at the lives of the rich and famous? These were not people ignorant of the world, but unfortunately, they could be innocent as lambs when faced with the greedy schemers and politicians of Brazil. And as the ongoing corruption scandals here evolve, it seems like nearly every politician serves their own or other greedy interests.
So it is understandable that the fishermen’s first thought was to go to the Catholic Church. But then we came. So they asked for Max’s advice.
The people of the village live simply with no luxuries except TVs. The town, located on a small island has no electricity except when the community generator is turned on at night. (Photo by C. Buiden.)
He quickly determined the fisherman had no idea they had legal rights to the fishery. He patiently explained the concept of ICMBio reserve system, the system of which they are a part. In theory, they could unify and certify their observations, take it to a judge and get a decision that would force the government to stop the theft by the international fishing fleet, at least in principle. Max and Danielle explained these rights and the group seemed sufficiently inspired. At least they left happy.
Why did they not know their rights? Max explained to me that the reserve manager for this area covered 60 other villages and that ICMBio has suffered 3 years of budget cuts. He reminded me how long it took to get to this village. So it’s the usual story familiar to U.S. agency biologists. Here, as it is in rural U.S., but with a more obvious impact, starving good government often only starves the people who live on the land, the land itself and the wildlife, who depend upon it.
For me, it meant something more. We proposed this project to create better protection for shorebirds. We took the usual approach. First, do the surveys then will create scientifically defensible descriptions of the habitat’s value. Finally, we overlay the threats: shrimp farming, oil spills, human disturbance, predators etc. then develop counter-measures.
I learned that nigh there is only one threat in this, one of the most important shorebird habitats in the world. It looms large above all others – if you erode ICMBio’s system of protection all the other threats will grow and decimate the fragile ecology of the area. Grow the ICMbio system and the traditional communities will enforce their legal right to conserve. They can monitor the threats and work with the agency to stop them. The laws already exist. The monitoring system is already in place. But this meeting pointed out they need more help.
Photos by C. Buiden.
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
The capture of Arctic nesting shorebirds first brought us to Brazil in 2013. We brought 125 geolocators and caught both ruddy turnstones and red knots, attaching 85 on the former and 30 on the latter. But we also came to create a new perspective on shorebirds in this place, one of the most important shorebird habitats in the world.
For all intents and purposes, shorebird work in this area started in the mid 1980’s, when Canadian biologists, Guy Morrison and Ken Ross surveyed from an airplane, the entire coast of South America. In this monumental and dangerous survey they established an invaluable historic baseline of the number of Arctic nesting shorebirds wintering in South America. This was before shorebirds caught the interest of the public, and way before foundations and agencies devoted significant funding or staff time. They surveyed the entire continent, but on the coast of Maranhao and Para they found the motherlode of shorebirds. They did not, however, get close and personal.
Guy Morrison and Ken Ross about to conduct an aerial survey (also in the photo is Guy’s daughter Clair, Brad Winn, Jorge Jordan and Luis Venegas).
That challenge belonged to a team led by the late Allan Baker of the Royal Ontario Museum and Ines Serrano, then with CEMAVE, the Brazilian counterpart of USGS. They also flew the coast but followed up with a ground survey and the capture of a small group of red knots. Along with Guy and Ken, their work cemented the hemispheric importance of this area.
Juliana holds one of the two birds caught in our second day of trapping. (Photo by C. Buiden)
Over the last 4 years we captured knots, turnstones, sanderlings, whimbrels, collared plovers, semi-palmated sandpipers, semi-palmated plovers as well as South American terns and other species. Last year we recaptured 20 geolocators in a catch of over a hundred ruddy turnstones. But only in 2013 were we able to catch red knots. Although abundant in the region, populations are estimated at 10 to 15K, they are remote and elusive.
So we were happy to find on our first day of surveillance this year over 400 red knots. They roosted within a flock of about 1000 shorebirds located at the west end of a small working class beach resort called Panaquatira, about an hour out of Sao Luis. The flock including black bellied plovers, semi-palmated sandpipers and plovers, collared plovers, South American terns, Black Skimmers and a few whimbrels. We readied that night for an early morning attempt.
First we needed to figure out the tide. It rises and falls 13 feet in northern Brazil, twice that in Delaware Bay. The spring tide or full and new moon tide increases the range to 18 feet. Consequently, the high tide line moves every day and catching birds with a cannon net depends on placing the net near the predicted tide line, because birds move with it to stay as far from the dangers lurking on dry land. Wind speed and direction changes the high tide line, and so does barometric pressure.
So much rides on where we place the net. On our first two attempts, we missed by just a few yards, but it could have been a mile. The birds moved with the tide and stood just outside the 30 by 100-foot area within which the birds must be to be caught. We tried moving them but they spooked and most gradually left the area altogether. Ultimately, we fired but caught only two knots and two whimbrels.
We were blessed on the third day. We arrived near dawn, over four hours before high tide so we had plenty of time to measure elevations. We knew the morning’s high would be about four inches lower than the previous night’s high, which snaked along the sandy peninsula used by the birds to roost. Standing on the tide line we used a method borrowed from Clive Minton to determine the location on the beach four inches lower.
Laying my head flat on the sand I trained my eye towards the horizon. This establishes a level line. Using her hand, Stephanie marks four inches on her leg than moves until the four inch mark lines up with the level line. Her location depends on the slope of the beach. In this way we determined the location of the tide line four hours hence. We dug in the net.
Larry Niles and Mandy Dey take training on measuring elevation from Clive Minton in Australia.
At about an hour before high tide, shorebirds started crowding into the area around the net. At first, oystercatchers, black bellies, short-billed dowitchers and a small flock of skimmers. Most of the knots hung back on an adjacent sand bar. With a little push, they too piled in right into the catch area.
We fired and caught 175 knots, 30 sanderlings, 20 short-billed dowitchers and 5 black-bellied plovers. Among the knots were 3 with geolocators. We flagged, banded and measured 145 birds, all the while releasing unprocessed birds that appeared stressed by the heat. By late afternoon we were back at the house cracking open beers. We completed all our objectives with one day to spare.
CWF Biologist Stephanie Feigin moves birds closer to the net. (Photo by Yann Rochepault.)
Stephanie and Julianna begin taking birds out of the cannon net. (Photo by Yann Rochepault)
We must cover birds with a light shade cloth to calm birds while they are extracted and placed into keeping cages. (Photo by Yann Rochepault.)
Processing our catch. (Photo by Yann Rochepault.)
One of the many values of catching shorebirds is examining their condition and molt. Here we compare two knots, an adult on the right and a second year or sub adult on the left. The latter molts its flight feathers much earlier than adults and it shows in the fading to brown. (Photo by C. Buiden).
Our team includes Carla Meneguin, Paulo Siqueira, Ana Paula Sousa, Larry Niles, Juliana Almeida, Carmem Fedrizzi Joe Smith, Stephanie Feigin, Yann Rochepault, Laura Reis and Christophe Buiden. (Photo by Juliana Almeida).
A red knot after banding and processing. (Photo by Y. Rochepault).
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
The Press of Atlantic City covered the troubling findings of Conserve Wildlife Foundation’s recent expedition to Tierra del Fuego in Chile to survey wintering red knots.
