Red Knots Expedited for ESA Listing

Red Knots and Dunlin feed together at Reeds Beach

I mentioned this in yesterday's Loose Feathers round-up, but I thought the news deserved its own post. It seems very likely that Red Knots will soon be listed under the Endangered Species Act. Such listing has been overdue for some time now, and several petitions have been filed with the U.S. Fish & Wildlife Service. So far it has lingered among the over 250 species on the candidate list. A plan to expedite review and listing of the candidate species was developed as a result of a lawsuit brought by WildEarth Guardians and the Center for Biological Diversity. From what I have read, the Red Knot will be near the front of the list, though formal listing might not come for a year or two.

What additional protections result from a listing remain to be seen, but conservationists have some suggestions:

Advocates say the listing would help not only the red knot, but many other shorebird species that migrate through Delaware Bay and are in a similar, although less dire, decline. These would include the ruddy turnstone, semi-palmated sandpiper and sanderling....

During the 1980s and '90s, peak Delaware Bay counts of the red knot reached 95,000.  Since 2004, they ahve been consistently below 16,000.  Likewise, in their wintering area at the tip of South America, peak counts have dropped from 75,000 to 16,260 in 2010.  At the winter count earlier this year, the number had declined to less than 10,000.

Meanwhile, a recent study by New Jersey biologist Larry Niles, who has followed the bird to the ends of the earth in a decade or more of study, and others has confirmed the key role that horseshoe crab eggs play.

"Right now, we need to see more adult crabs breeding, and we're not," Niles said. Fisheries officials that govern the crab harvest keep saying to give it more time, he said. "That would be fine, except we were promised signs of recovery six years ago."

He suspects further restrictions in the harvest are needed. Or the problem now may lie elsewhere. The illegal harvet may be greater than estimated. The blood of the crab is used as an indicator for contamination in medical devices, and the crabs are caught, partially bled and then returned to the wild. But a recent study suggested that mortality from this may be higher than estimated.

I wrote about the study connecting Red Knots to Delaware Bay stopover habitat last week.

Habitat protections might also result, though a lot of the Red Knot's habitat falls outside of the U.S. – in Canada for breeding and in southern South America for wintering. Either way, it is a positive step forward, and I hope it results in a stronger Red Knot population.

Study Confirms Importance of Red Knot Migratory Stopovers

As many readers know, Red Knots (Calidris canutus rufa) are in serious trouble.* Though they were once an abundant shorebird during spring migration on the Atlantic Coast, their population crashed in the 1990s. This winter, Red Knots suffered another setback, when a third of their current known population disappeared from the wintering grounds for reasons that are not entirely clear. The major crash in the 1990s has long been linked to food availability at migratory stopover sites.

During spring migration, Red Knots time their arrival in the Mid-Atlantic to coincide with the spawning of horseshoe crabs. Red Knots (and other shorebird species) eat the freshly-laid eggs to gain weight for the final leg of their journey, from the Mid-Atlantic to the Arctic, where the birds need to find mates and breed within a fairly short window of time. A major increase in the harvest of horseshoe crabs, due to their increasing use as bait for whelk fishing, reduced the availability of horseshoe crab eggs. While some shorebird populations remained stable or suffered small decreases, the Red Knot population crashed.

A new study, published in the open access journal Ecosphere, confirms the importance of stopover habitats – and the food sources they provide – for migratory shorebirds. The study uses data collected during a multiyear banding project of shorebirds around Delaware Bay. (As readers may remember, I participated in one such banding session earlier this year.) The study used two types of data from the project: captured or recaptured birds with known identities and known weights and resighted birds with known identities but unknown weights. The project has been banding Red Knots and other shorebirds with metal bands since 1997; in 2003, it started tagging Red Knots with colored bands bearing alphanumeric codes that can be read with binoculars or a spotting scope.

The study used mathematical models to determine the relationships between spawning by horseshoe crabs and weight gain by Red Knots and between Red Knots' mass at departure and future survival. (You can read the study's methods section for a technical description of the models.) The results showed that how much weight Red Knots gain depends not so much on the overall horseshoe crab abundance but on the timing of horseshoe crabs are spawning. If horseshoe crabs spawn later than usual, Red Knots are not able to gain as much weight as they normally would because not enough eggs will be available before they have to depart for the Arctic. Weight gain at stopover sites is crucial since Red Knots with a light weight at departure were unlikely to be recaptured or resighted in subsequent years.

While the model found a correlation between weight gain and subsequent survival, it found a stronger relationship between survival and snow depth on the Red Knots' breeding grounds. Red Knots were more likely to survive from one year to the next if there was deeper snow on the ground when they arrived in the Arctic. The scientists offer several possible explanations. One is that greater snow depth means greater overall moisture, which increases the amount of invertebrate prey available for the Red Knots. Another is that lemming populations tend to crash in years with low snow depth, so in those years predators that normally eat lemmings might turn to shorebirds instead. Determining whether those or other hypotheses are correct will require further research in the Arctic.

The study reinforces the link between horseshoe crabs and Red Knots and the importance of Delaware Bay as a spring stopover site. All necessary efforts should be taken to ensure that the bay continues to provide adequate habitat and food for these long-distance migrants. Such efforts should include further restriction of horseshoe crab harvests, particularly in Delaware, which has continued to allow harvesting even though New Jersey has imposed an indefinite moratorium.

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Cited study:
McGowan, Conor P., James E. Hines, James D. Nichols, James E. Lyons, David R. Smith, Kevin S. Kalasz, Lawrence J. Niles, Amanda D. Dey, Nigel A. Clark, Philip W. Atkinson, Clive D. T. Minton, and William Kendall. (2011). Demographic consequences of migratory stopover: linking red knot survival to horseshoe crab spawning abundance. Ecosphere, 2 (art69) : 10.1890/ES11-00106.1

* For international readers, the IUCN ranks Red Knot as a species of least concern; the discrepancy is that there are multiple subspecies, and many of them are secure. However, the western Atlantic subspecies – the one that breeds in the North American Arctic, migrates along the Atlantic Coast of North America, and winters in Tierra del Fuego – is in serious danger of extinction.

Some Red Knot News

Last week, I had the privilege of helping with Red Knot banding in Cape May. A reporter from my local newspaper spent some time with the shorebird banding crew recently and filed a story on the current status of Red Knots. Things are still looking dire, despite some New Jersey's moratorium on the horseshoe crab harvest.

Now the federal government might make a decisive move. The red knot is a priority in a new plan by the U.S. Fish and Wildlife Service to deal with a backlog of 250 animal and plant species proposed to be covered by the Endangered Species Act....

But meanwhile, horseshoe crab harvests in other states might be increased when the Atlantic States Marine Fisheries Commission meets later this year, she added. And scientists are concerned because a key crab survey by Virginia Tech lost its federal funding this year and is just halfway toward raising the $200,000 cost.

Delaware Bay is the big stopover for red knots’ flying north to breeding grounds in Canada, because their migration coincides with the horseshoe crab breeding season that leaves bay beaches littered with nourishing crab eggs. That fattens the birds and gives them energy to push on north and lay eggs, said Niles, chief scientist for the Conserve Wildlife Foundation of New Jersey....

New Jersey shut down its commercial fishery for horseshoe crabs in 2006, culminating years of cutbacks after the take of crabs for fishing bait was blamed for the red knots’ decline. But after 6,000 birds went missing from their South America wintering grounds, researchers think the problem may be down south, Niles said.

Researchers in Argentina reported toxic red tide algae blooms may have killed some birds before they reached their winter quarters, at the southern tip of the continent at Tierra Del Fuego. The drop in the winter count, to 10,000 birds from 16,000, may show growing dangers to the birds all along the western Atlantic and Caribbean shores, said Niles, a former chief of New Jersey’s endangered wildlife program.

Banded shorebirds now carry small flags that can be read with a spotted or from a photographic image. These flags, along with any codes they bear, should be reported at bandedbirds.org. Here is some background information on the website: 

“If you are the first one to see the re-sighting, we know the bird is still in the flyway,” said Jeannie Parvin, who manages the website www.bandedbirds.org. “Just that information is very important. It’s not just for red knots, it’s for all the shorebirds.”

The website supports the Delaware Bay Shorebird Project, a 15-year effort that has built perhaps the world’s biggest database on migrating shorebirds within a flyway. Like a highway for people, a flyway is a track that birds follow between their southern winter homes and summer nesting grounds in the high Arctic of Canada.

Bandedbirds.org offers pages explaining shorebird research, how to read tags on birds and estimate bird counts. After a one-time registration, contributors can send in sightings that go immediately into a database for researchers to use, Parvin said.

Finally, there has been some research into the feasibility of raising horseshoe crabs from eggs in captivity and releasing them once they are better able to survive predation.

Woodruff works at the university's aquaculture facility in Lower Township, where the staff cultivates oysters. But they are looking to expand their scope to raise horseshoe crabs from eggs for release back into the wild to give the creatures a head-start against hungry predators.

"Everything eats them. Basically, we want to farm them - take their eggs and raise them until they are big enough to survive on their own," Woodruff said.

Such human intervention could solve a conflict between local fishermen and conservationists. New Jersey's ban on crab harvesting remains in place in a bid to build up the number of spawning crabs and their bounty of eggs, which are critical for feeding rare shorebirds such as red knots that gather on the bay to fatten up during their epic migrations from the Arctic to South America.

Daniel Hernandez, an assistant professor at The Richard Stockton College of New Jersey, counts crab eggs on the beach each year for his ongoing research. The Stone Harbor resident said egg counts have dropped precipitously from their historic levels....

A 2009 study in the journal BioScience, which Hernandez took part in, said that in 1990 more than 100,000 crab eggs per square meter were found on Delaware Bay beaches.

"Now they have 5,000," he said.

I hope that works to rebuild their numbers because the number of horseshoe crabs eggs is critically low to support Red Knots and the other shorebirds that depend on them. The same news article mentions that there will be horseshoe crab tagging sessions open to the public at 8:30 pm on May 31 and June 2 at Kimbles Beach in Cape May NWR. If you're in the area, it might be worth checking out.

Some More Shorebird Photos

These are a few additional photos that I took on Saturday, but that did not fit into my post on shorebird banding yesterday. Up above, a group of Dunlin pause in the surf, with a Semipalmated Sandpiper standing by.

A Dunlin forages in the foreground while Red Knots stand in the surf.

A familiar trio from Reed's Beach: Red Knot, Laughing Gull, and Dunlin.

A Semipalmated Sandpiper picks through beach litter for morsels.

A Laughing Gull stands in the surf.

Speaking of Laughing Gulls, this is what Reed's Beach looked liked on Sunday morning. Cape May County has one of the largest Laughing Gull breeding areas in the world in its back bay marshes along the eastern side of the peninsula. Apparently a lot of those nests got flooded out in the last week because of recent high tides, made higher than normal by their proximity to the full moon on Tuesday. As a result, a lot of those gulls were hanging out in the horseshoe crab spawning areas along the Delaware Bay instead of tending to their nests in the marshes.

Shorebird Banding in Cape May

As many readers are aware, conservation of shorebirds that use the Delaware Bay as a migratory stopover is a pressing issue. Many species, such as Red Knots and Ruddy Turnstones, time their migration to arrive at the bay just as horseshoe crabs are laying their eggs on the beaches. Shorebirds feed on those eggs to regain the weight they lost during their flights from wintering grounds in South America and prepare for another long flight to their Arctic breeding grounds. For a long time this arrangement worked well, but in the 1990s, overharvesting of horseshoe crabs (used for fishing bait and medical research) caused a crash in the Red Knot population. States have taken some steps to limit the horseshoe crab harvest (including New Jersey's legislative moratorium), but the Red Knot's survival remains tenuous. The population has fallen enough to earn the Red Knot a place on the USFWS's candidate list but so far it has not been listed as threatened or endangered by the federal government.

An international effort is underway to monitor the remaining population and push for conservation of the habitats and resources the Red Knots need. Part of that is an ongoing banding program to study how birds use stopover sites and what migration routes they use. My friend Mary (whom I met through DC Audubon) knows some of the banders from her time in Australia, so she got invitations for the two of us to participate in a banding session this past weekend. Because of weather and tides, it turned out that Saturday was our best chance to participate, so we made sure to be at Reed's Beach early in the morning, even though we both arrived in Cape May rather late the previous night.

You can see how shorebirds are banded in a video I linked on this blog a few years ago. That shows a different set of banders in a different location, but the methods for capture and processing are essentially the same. The banding team prepares a net and disguises it as carefully as possible. Once enough shorebirds are in front of the net, the team fires cannons that propel the net over the birds. Some birds will escape, but many will be caught under the net. The banding team hurries to extract the birds from under the net as quickly as possible, so as to avoid unnecessary stress or injuries to the birds. Once all the birds are out of the net and into shaded containers, the banders can sit down and process them.

On Saturday, the captured birds went through several steps before their release. First they were banded and marked with coded tags to make it easier to recognize individuals in the field without recapturing them;* then a series of measurements were taken: weight, wing chord, and bill and head length; finally, feather samples were taken for lab analysis. One person recorded all of the codes and measurements for each bird. I was last in line, so I held each bird while another person snipped some feathers (one wing covert and two breast feathers), and then I released it. I think I probably handled a few dozen Red Knots in the course of the morning, though I was not keeping count.

It was really cool to hold the Red Knots and see them up close. One thing I had not realized when I looked at them through binoculars was just how intricate the patterns on their backs are. Their scapulars in particular have dark brown lines dividing each feather into sixths; the middle part of the feather is tinged with rufous while the tip is white. Meanwhile, their rumps are etched with fine barring, and their undertail coverts are speckled. The Red Knots were also smaller than I expected; I guess they look larger to me through binoculars than they do in the hand. A lot of these birds were recent arrivals, though, so it is possible I would get a different impression once they had time to gorge themselves on horseshoe crab eggs.

As I mentioned in yesterday's post, Mary and I went to Heislerville in the afternoon and evening to find a Curlew Sandpiper. Once we had found it, we helped with another banding project that is monitoring some of the species using the impoundments. That project is mainly concerned with Semipalmated Sandpipers, but it also bands Short-billed Dowitchers, Dunlin, and other shorebird species that happen to get tangled in the nets.  Mary helped extract shorebirds from the nets, while I ferried birds from the nets to the banders or held nets so that they would not blow on a bird during the extraction process. Once again I was impressed by the birds' small size; the Semipalmated Sandpipers were especially tiny.

I really enjoyed my experience with shorebird banding this weekend, and I hope to do more of it when I have the chance.

* If you happen to see a Red Knot (or other shorebird) with color markings or a colored flag with an alphanumeric code on it, please report it to bandedbirds.org.

Red Knot to be Listed as Endangered in NJ

New Jersey's Department of Environmental Protection is proposing to change the state's listing of Red Knot from threatened to endangered. The proposal is based on a few years of studying their population trends, but it was made more urgent by recent reports from South America:

In late February, biologists returned with sobering news from their annual trip to the bird's wintering grounds in Tierra del Fuego, Chile.

Immense flocks of red knots once swooped over the vast tidal mudflats, rich in tiny organisms that were a nonstop banquet. In recent years the number declined to 16,000, but remained stable.

Now, the count showed the population dropping again, to between 10,000 and 11,000.

"We're dismayed," said Larry Niles, former chief of the DEP endangered-species program, now a wildlife consultant. He has led red knot research for more than a decade.

The crew of more than a dozen international researchers had hoped for an uptick because conditions on Delaware Bay last spring were so favorable. The weather held, the crabs laid their eggs, the birds feasted.

Data from netted birds showed that nearly 80 percent were at or near ideal body weight, prime for breeding.

An online version of the state's proposal is here, for anyone who wants to read and comment on it. Comments must be received by March 19. It looks like comments have to be submitted by mail even though NJDEP asks for an electronic copy.

The Amazing Flights of the Red Knot

Scientists have been able to trace the annual journeys of individual Red Knots using tracking devices attached to the birds' legs. (I linked to an article on this in my last Loose Feathers edition, but I think it deserves its own post so that it does not get lost among the other articles.) Prior to this study using geolocators, the general outline of the birds' migration was already known: most Red Knots winter in Tierra del Fuego, make migratory stopovers along the Atlantic coast (especially Delaware Bay), and breed in Arctic Canada.

The geolocator study added some detail to the general picture and emphasized just how important horseshoe crabs are for Red Knots' survival. The bird whose data is presented in the graphic at right (click to see a larger version) made several nonstop long-distance flights, including one over 2,000 miles, another over 3,000 miles, and a third of almost 5,000 miles. The last of those flights crossed the Amazon, the Caribbean, and part of the Atlantic before it terminated in Ocracoke, North Carolina, right around the time that horseshoe crabs would be spawning. At that point, the bird would be tired, starving, and in need of some quick nutrition in the form of fresh horseshoe crab eggs.

The study was funded by the U.S. Bureau of Ocean Energy Management, Regulation and Enforcement, which wanted better data on how offshore wind energy projects might affect Red Knots, Piping Plovers, and Roseate Terns – three vulnerable species that migrate or breed along the U.S. Atlantic coast. Several wind farms are already planned in the vicinity of Delaware Bay.

Here is a bit more about the technology behind the study:

Basically, the geolocators determine location by measuring daylight. The length of a day shows the bird's latitude, and the time of local "noon" - when the sun is at its highest - shows longitude....

Far better devices exist than even the geolocators, but only for larger birds. Several years ago, Pennsylvania officials outfitted a peregrine falcon with a solar-powered backpack that transmitted fixed GPS locations to a land-based receiver - allowing scientists to fly along virtually via a laptop.

The geolocators were developed by the British Antarctic Survey in England. Every year, they are able to tweak the technology to get a smaller instrument, said James Fox, an electronics engineer with the Survey.

The problem is that the devices for the red knots need to be so small that it's impossible to add the capability to transmit. To get the data, the scientists have to find the birds and recapture them.

The scientists capture and tag the birds at Delaware Bay since so many Red Knots gather there during the spring and then recapture them at the same site the following year. So far 47 Red Knots have been tagged with geolocators and three have been recaptured. When (if?) the other birds are recaptured, there will probably be more interesting tales in the data.

The full article is well worth a read.