DE-Shorebird-ProjectDelaware Shorebird Project
2016 Field Season Report

shorebird 5Every spring, hundreds of thousands of shorebirds travel through the Delaware Bay as they migrate from areas as far as southern South America to the Arctic, where they breed in the summer. The Delaware Bay is a crucial rest stop, where the birds eat horseshoe crab eggs for sustenance.

DMNH’s Director of Collections and Curator of Birds Jean Woods, Ph.D. is a team leader with the Delaware Shorebird Project, conducting field work, coordinating activities and training volunteers. The Delaware Shorebird Project is managed by the Delaware Department of Natural Resources and Environmental Control’s Division of Fish and Wildlife’s Natural Heritage and Endangered Species Program.

Below is the project’s 2016 Field Report.

The Delaware Shorebird Project, managed by the Division of Fish & Wildlife (DNREC), is pleased to present this report of their 2016 field season. The project was established in Delaware in 1997 to study the shorebirds that migrate through Delaware Bay each spring. At that time there was great concern about declining shorebird numbers, especially Red Knot, and the overharvest of horseshoe crabs. Some of the areas of research that we’re focused on include population sizes of shorebirds using the bay, their response to limits on horseshoe crab harvest, duration of visits to the bay, weight gain, and areas used by the shorebirds.

The results of our research have led to a better understanding of the ecology of the shorebirds that migrate through Delaware Bay. Management of the important horseshoe crab population has been improved and key habitat has been protected. We’ve very excited about the restoration project currently under way in Mispillion Harbor, one of the key sites for shorebirds on the Delaware side of the Bay.

We hope you enjoy these highlights of the research our Shorebird Team conducts every spring during shorebird migration. Visit NJ Fish and Wildlife to learn about our sister project, the Delaware Bay Shorebird Project and the shorebird research they do in New Jersey! Click here for a downloadable PDF of the report.

Audrey DeRose-Wilson, Delaware Shorebird Project Manager, deshorebirds@gmail.com

Every spring, the Delaware Bay is host to an extraordinary phenomenon – hundreds of thousands of migrating shorebirds and horseshoe crabs amass on the Bay’s shores. The crabs come to spawn and lay millions of tiny green eggs which the shorebirds come to eat. The Delaware Bay is a critical stop over point for migrating shorebirds to rest and refuel, some of whom have already traveled 7,000 miles. They are heading to their Arctic breeding grounds and need to consume enough protein rich crab eggs to almost double their body weight before departing on the last 2,000 mile leg of their journey north!
But current shorebird numbers are at low compared to past years, particularly the Red Knot (Calidris canutus rufa), and the yearly phenomena that visits the Delaware Bay could be in danger of disappearing if further population declines occur. The Delaware Shorebird Project began in 1997 in response to the sudden drop in shorebird numbers observed during the early 1990s with the hopes of discovering the cause of the population crash. Now entering its 20th year of research, the Delaware Shorebird Project continues to identify and protect the resources vital to ensuring the successful migration of shorebirds each year.
Following the arrival of the first early migrants in May, the Delaware Shorebird Project’s team of volunteer citizen scientists and State, Federal, and international researchers converges on Delaware’s bay beaches to begin another season of shorebird research. The Shorebird Team dutifully collects data each year by daily walking beaches counting shorebird flocks, trapping shorebirds to assess health, and looking for marked or flagged individuals. The 2016 season saw 55 volunteers from the UK, the Netherlands, and 11 states contribute over 3,600 hours to shorebird research in the Delaware Bay!
In addition to carrying unique identifying codes, the color of the flag identifies where the bird was originally flagged. Each color represents a different country or group of countries as indicated on the map to the left. For example, the Red Knot featured at the top of the page wears red flag HMN signifying that it was flagged in Chile. The Semipalmated Sandpiper pictured on the bottom right has a blue flag reading AK8 indicating that it was flagged in Brazil. Orange flag CNP on the Red Knot at the bottom left shows that it is an Argentinian flagged bird.
During the 2016 field season, the Delaware Shorebird Team identified over 3,600 uniquely flagged individuals among the hundreds of thousands of shorebirds that visited Delaware. The map on the following page divides up the total number of resighted Red Knots, Ruddy Turnstones, and Sanderlings observed by our Shorebird Team based on flag color. Unsurprisingly, the majority of flagged shorebirds resighted this year were flagged in the US with green flags. Several other countries were also represented including Argentina, Brazil, Canada, the Caribbean, Chile, Mexico, and Surinam.

In addition to carrying unique identifying codes, the color of the flag identifies where the bird was originally flagged. Each color represents a different country or group of countries as indicated on the map to the left. For example, the Red Knot featured at the top of the page wears red flag HMN signifying that it was flagged in Chile. The Semipalmated Sandpiper pictured on the bottom right has a blue flag reading AK8 indicating that it was flagged in Brazil. Orange flag CNP on the Red Knot at the bottom left shows that it is an Argentinian flagged bird.
During the 2016 field season, the Delaware Shorebird Team identified over 3,600 uniquely flagged individuals among the hundreds of thousands of shorebirds that visited Delaware. The map on the following page divides up the total number of resighted Red Knots, Ruddy Turnstones, and Sanderlings observed by our Shorebird Team based on flag color. Unsurprisingly, the majority of flagged shorebirds resighted this year were flagged in the US with green flags. Several other countries were also represented including Argentina, Brazil, Canada, the Caribbean, Chile, Mexico, and Surinam.

shorebird-flag-map

shorebird-geographic-map

By flagging shorebirds, researchers can learn more about their movements – their migration pathways of choice, where they winter, where they nest, and what stopover points they visit. The map to the left highlights the known locations that Red Knots frequent but there are certainly other destinations that remain undocumented.

Flagging is also used to estimating stopover population size, individual survival rates, and survival of the species as a whole. No one knows exactly how long Red Knots can live but their average lifespan is between 4 to 7 years. The life of a Red Knot is challenging and migration holds many dangers including predators, severe weather, threats to food supply, and the disappearance of good habitat. But Red Knots are born survivors and there are some who continually beat the odds year after year. Like Moonbird.
Moonbird is the nickname given to the oldest known Red Knot. He was at least 2 years old when he was flagged as orange B95 in Tierra del Fuego, Argentina in 1995. Today, Moonbird is at least 23 years old and continues to make his long 18,000 mile yearly journey between Argentina and Canada. He has made this trip so often that he has flown over 400,000 miles –the equivalent of flying to the moon and almost all the way back! B95’s incredible journey can be seen mapped out on the next page. Moonbird has been seen many times and in many locations since he was first flagged, occasionally disappearing for long stretches of time. He was last seen in northern Canada in 2014.

The Delaware Shorebird Project routinely traps shorebirds in the spring to assess the health of the flock and to flag new individuals. When shorebirds are trapped, each bird is first outfitted with its own unique flag before other data like age, weight, sex, and body measurements used to assess the condition and health of the bird are collected.

During the 2016 field season, the Shorebird Team caught over 1,700 shorebirds including Red Knots, Ruddy Turnstones, Sanderlings, Semipalmated Sandpipers, Short-billed Dowitchers, and Dunlins. One particular Ruddy Turnstone that was caught this year has become famous for his swift es-cape after receiving his flag but before any other data could be collected. The three letter code on his flag? It reads 007!
Almost all shorebirds that visit the Delaware Bay during spring migration arrive somewhat emaciated like the Sanderling in the top photo. They can be expected to almost double their body weight within their two week stay. Not only do they need to recover from their several thousand mile journey to Delaware but they also need to gain weight to sustain them on the 2,000 mile journey to the Canadian arctic where food may not be readily available for several weeks. During this time, they must establish territories, mate, prepare a nest, and lay eggs timed perfectly to hatch coinciding with the arrival of a massive insect food supply.
But they have to be careful, if they eat too much, they may end up like the Sanderling in the middle picture and be too heavy to fly! Such was the case with one Sanderling that trapped this year. This rotund little bird weighed in at an astonishing 106g, overshooting the desired departure weight of 85g! He gained so much weight that he was unable to fly and instead waddled slowly down the beach be-fore resuming normal shorebird activities.

One of the most indicative sign of a healthy shorebird flock is successful weight gain. When Red Knots first arrive in Delaware, they weigh on average 120 grams. During their stay in the Delaware Bay they must feast on enough Horseshoe Crab eggs to bulk up to 180 grams. They need the extra weight to sustain them on the last leg of their journey north and well into the breeding season.

Food availability is not guaranteed upon arriving in the Arctic. The graph below depicts the average overall body mass for each of our target species gathered from six trap days. The points on the figure represent the average body mass of birds weighed during a single catch. Overall, the graph shows that average body mass increased for all shorebirds shorebird species trapped during the progression of the 2016 spring shorebird migration.

 

weight-of-a-bird

The research that we do, past and present, would not be possible without the continued contribution of our collaborators at the US Fish and Wildlife Service (USFWS), the Delaware Museum of Natural History (DMNH), the British Trust for Ornithology (BTO), and the Wash Waders Ringing Group (WWRG).

This project would not perform at such a high caliber without their incredible dedication, commitment, and the expertise that they bring to the project each year. Equally important are our dedicated volunteers. It is because of their hard work, talent, enthusiasm, and commitment to shorebird research that allows us to collect such an extraordinary amount of valuable data every year. Thank you for another successful field season.
Anyone interested in volunteering for the 2017 Shorebird Field Season should visit us at Delaware Shorebird Project to learn how. Be sure to also check out the links below to learn more about Red Knots, other shorebird migrants, Horseshoe Crabs, and ways you can help!

Delaware Museum of Natural History
Conserving Shorebirds in the Atlantic Flyway
Just Flip EM (Horseshoe Crabs)
Red Knot (Audubon)
Birders Can Help! (E-Bird)

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Download the PDF of the 2016 Field Season Report from the Delaware Shorebird Project

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