Feast on the Beach: The Delaware Bay Horseshoe Crab Shorebird Connection

Feast on the Beach: The Delaware Bay Horseshoe Crab Shorebird Connection



the full moon in May brings up drama there's an epic journey a great feast an ancient mating ritual fierce competition struggles for survival and dedicated people committed to saving it all best of all it's true and it happens each spring right here on Delaware Bay [Applause] every spring seemingly out of nowhere almost a million shorebirds appear on the shores of Delaware Bay most arrive around the second week of May and then vanish by early June one brief month but they're not here by accident they're here because of another annual spring visitor the American horseshoe crab that appears in huge numbers at the same time carpeting Delaware Bay beaches the shorebirds are on their annual journey north to the Arctic many have migrated from the tip of South America where they have spent the southern hemispheres summer feeding on small clams and mussels found in the vast mud flats there but with winter arriving below the equator and spring warming the northern hemisphere they are now headed north on an epic journey of ten thousand miles to the Arctic where they will mate and lay their eggs to reach Delaware Bay some of these shore birds have flown as many as 1,500 miles non-stop where they've learned there is a feast waiting for them provided by hundreds of thousands of horseshoe crabs they have migrated here for their own purposes to spawn and lay their eggs relatively unchanged for over 400 million years horseshoe crabs are one of nature's oldest creatures they have outlived dinosaurs survived ice ages and even continent formations to survive this lawn means they've adapted well and one of their unique adaptations is to use the warm beach sand to incubate their eggs and since Delaware Bay is relatively shallow with plenty of gently sloping sandy beaches it is the best place on earth for horseshoe crabs together spawn and deposit their eggs beginning in early May prompted by longer days and warming waters thousands of female horseshoe crabs make their way into Delaware Bay and towards the sandy beaches with each high tide and especially with the new and full moon the females come ashore but not before waiting male crabs attach themselves in hopes of fertilizing their eggs the larger females dragging the smaller males behind them leave the water seeking to lay their eggs as far up on the beach as possible since there are many more males than females they compete to be in the best position to fertilize the eggs pushing and shoving each other on top of the females even as the females dig down in the sand to deposit their eggs once in position the female lays a clutch of 2,000 to 4,000 grayish-green eggs which are fertilized externally by the attached males she moulds the egg clutch with coarse sand to ensure it will remain intact beneath the sand while the eggs incubate during each tide cycle a female may lay four or five egg clutches and then return to the bay as the high tide waters recede she will return with the next high tide repeating this process until she is deposited as many as 100,000 eggs if all goes well the warm sand incubates the eggs and they hatch in about a month's time the young larvae worked their way up to the surface and are carried into the bay in nine or ten years they mature and return to spawn and may live as long as twenty-five years but for many eggs things do not go well many clutches are disturbed either by the bays wave action or by successive spawning females who inadvertently dig up previously led clutches these come to the surface are broken up and soon millions of loose eggs are awash in the water and spread over the shoreline and usually by early May there is a shorebird feast on the beach but now another group of visitors arrives on Delaware Bay an international team of researchers congregates every year along with the birds along the Delaware coastline and everyone works together to recite as many birds as we can then capture birds and collect more symmetric data officially known as the Delaware shore bird project this team of international scientists federal and state biologists and dedicated volunteers has been studying this migration for two decades some critical data can only be gathered by catching the birds using nets propelled by cannons the team must wait for just the right mix of birds in the catch area the team works quickly to minimize the stress on the captured birds sorting and placing them in boxes as they are taken from the net we've got a really nice catch again if you are not then we would have really liked we'd hope we caught more knots we'd hope to get over 30 knot we've probably only got 20 which is a shame but we'll get some weights on them some of these birds have only just arrived so it'll be really interesting to see what what they weigh now because they'll be coming in quite light around 100 grams and in the next couple of weeks they're going to put on another hundred grams double their weight in two weeks amazing things red knots are classified as a threatened species under the Endangered Species Act and therefore a major focus of the team's study they're about the size of a Robin with a similar red breast which is their mating plumage like the other shorebirds they have traveled thousands of miles non-stop and often arrive just feathers and bone once here they must feed voraciously on the fat rich horseshoe crab eggs to quickly gain enough weight so they can continue migrating north their weight gain is remarkable as much as four to nine percent per day which means they usually double their body weight in about two weeks but there are other bird species the team is monitoring as well ready turn stones at the feistiest shore bird and one of the only shorebirds that can actually dig for eggs semi palmated sandpipers are one of the smallest shorebirds often called peeps they have Buffy white breasts they can usually be found feeding right at the water's edge Sanderlings are also a type of Sandpiper but about twice the size of a semi and have a reddish tinge to their feathers many different bird species appear on the bay beaches as well from the fairly common Dunnellon to the exotic looking black necked stilt but all are here for a common purpose to feast on the abundance provided by the horseshoe crabs horseshoe crabs are not only important for the birds they're important for humans as well in the past they were harvested by the millions for use as fertilizer and more recently harvested by water men for use as bait for eels and conch but perhaps their greatest value to us is found in their blood which is 1 million times more sensitive to certain bacteria than our own for this reason an extract in their blue blood called Lal is used to test the sterility of every needle artificial limb and injected drug used in the medical industry today in short we need horseshoe crabs as much as the shorebirds do which is why their harvest is now regulated and why they like the shorebirds are monitored as well spawning female crabs used the high tide to get up as far on the beach as possible and the largest number of animals appears with the highest tides which occur in the evenings of the new and full moon so with each lunar event in May and June volunteers and 17 baby to spend their nights sampling the horseshoe crab population we get numerous volunteers citizen scientists to come out help us conduct these surveys and the great thing is the data that are generated in this survey and other similar surveys is used to manage the horseshoe crab resource another way horseshoe crabs are being monitored is with tagging biologists and volunteers have been doing this as part of a Coast wide US Fish and Wildlife study since 2003 despite their slow movements horseshoe crabs can travel great distances over time if a citizen scientist or beach Comber finds a tagged crab later on another Beach they can call in the crabs unique number learn where it was first caught and tagged and helped fisheries managers better understand the movements of the overall horseshoe crab population but it's not just the crabs that are tagged properly monitoring migratory shorebirds includes assigning a special flag to each captured bird the flags colors signifies the country where the bird was caught with green meaning the United States a unique alphanumeric code is printed on each flag so teams of scientists and volunteers can monitor sherbert numbers and movements along their migration routes and around Delaware Bay throughout their brief stopover when we go out to look for these birds with flags on them we'll take our spotting scope and our binoculars and most importantly our field notebook and we'll go to our assigned Beach we try to cover all of the beaches we're looking for red knots ready turn stones Sanderlings and then we'll just search through the Fox of birds looking for a bird with a flag when we see a flag we need to read the code that's on the flag it's typically two or three letters or numbers and that will record that information on our field notebook when we get back to the research base we will transcribe all of that information onto a data sheet and then that data gets entered into the database this growing database is helping scientists better understand the life cycle of these long-distance migrants who might live 20 years and travel up to a quarter million miles but it's an annual challenge given the brief time the birds are here and the many beaches where they can feed the team must work long hours to gather and process as much data as possible yet they also realize it's important to share this amazing experience with the public it's absolutely world-class it's obvious it's absolutely unique in the world and I think people should when they can in an appropriate manner without disturbing the birds come and take advantage of that and see it fortunately the Miss pinion harbor reserve where much of the shore bird research takes place is also the home of the DuPont Nature Center established by the state in 2007 the center's displays explain this amazing phenomenon to an increasing number of visitors each year it's a convenient place where researchers can share their knowledge and the public can easily view this world-class spectacle and enjoy events such as the annual peace love and horseshoe crab festival but Delaware is also committed to maintaining the habitats necessary to sustain this natural wonder in early 2017 with federal assistance State replenished the harbour beaches specifically designing them to meet the requirements of spawning crabs and shore bird flocks in addition the nonprofit group er DG has partnered with ten Bay Shore communities to conserve horseshoe crabs towards backyard stewardship program communities established crab sanctuaries and promote the just flip um initiative with the goal of helping stranded crabs used to be years ago you'd walk the beach and you'd see a footprint in the sand and you'd see a crab overturned and now since we became the horseshoe crab sanctuary we ended up having a lot more people that actually now getting out and flipping horseshoe crabs they there you go the morning walk and what do you do you flip crab a month later and another full moon the shore birds are gone and now in the barren Arctic most have already made it nested and hatched their chicks timed so that the young birds can feed on the millions of insects that hatch at the same time soon the adult birds will begin their long journey south leaving the young to follow later on their own for some a journey of nearly 10,000 miles meanwhile in Delaware the shore bird project team has departed as well leaving local biologists to process this year's data and time to reflect on the project's achievements due in large part to volunteer participation I think this is one of the best volunteer citizen scientist projects I've ever seen but for a couple reasons one is that they're out on the beach where they're seeing birds that they know are really important and are somewhat accessible and they can see that worship crabs really easily but also because we can bring people who don't know a lot about how to handle birds and integrate them into the team because of the way we've set this up on the same full-moon other volunteers survey the horseshoe crabs one last time before they depart and return to the ocean by the end of June the Bay beaches have regained their solitude making it hard to believe this great drum has even taken place challenging all those who'd like more people to see and experience it this phenomenon is worth everyone's attention we have people in close proximity to this resource that have little idea that this is occurring basically right outside their doorstep and it is a spectacle that you must see to appreciate whether practicing community conservation collecting scientific data or simply experiencing it for the first time the horseshoe crab migratory shorebirds Rama has once more proven nature's ability to amaze us and inspire us to you and protect our natural world

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