When CWF began monitoring American oystercatchers nesting on the Delaware Bay this past spring, we also set out to place field-readable bands on as many oystercatcher adults and chicks as logistically possible. Band resights allow biologists to collect a wealth of information about site fidelity, habitat use, dispersal, and migration, especially when data is collected over many years. Since the Delaware Bay population of oystercatchers was previously unmonitored, we have a lot to learn about their life histories and how they may differ from other oystercatchers in the state, if at all. Where are these birds staging and wintering? Do breeding adults return to the same mates and nesting locations each year? Where do fledged chicks disperse, and will they return to their natal grounds on the Delaware Bay to breed upon reaching sexual maturity? Banding efforts, combined with resight data reported by biologists, dedicated volunteers, and the general public will help answer these questions (and more) as we increase the number of marked individuals on the Bayshore.
Orange C41 (aka “Crouton”) being equipped with a metal federal band on the lower leg. The color of the field-reable bands on the upper legs represents which state the bird was banded in (New Jersey and New York use orange), while the alphanumeric code on the band is unique to the individual bird. All handling of birds is conducted by trained individuals under proper permits.
This past winter, CWF announced a new project designed to study and monitor the population of American oystercatchers breeding along the New Jersey side of the Delaware Bay. In addition to locating nesting pairs and tracking their success, our goal is to better understand how oystercatchers utilize the bayshore habitats and what factors threaten their productivity. The data we gather with our partners at The Wetlands Institute and U.S. Fish and Wildlife Service will be used to inform future management decisions. We spent the past few months working hard to conduct the project’s first season of monitoring, and we are happy to say that we have made significant progress in beginning to unravel the mysteries surrounding this understudied population.
Delaware Bay American oystercatcher study area. Most oystercatcher pairs this season were concentrated in the bay beaches between Stipson Island and Heislerville WMA.
Since so little is known about this subpopulation of oystercatchers, we had a lot of ground to cover in our first season of fieldwork. First, we had to locate any breeding oystercatcher pairs across 35 sites spanning approximately 45 miles of bayshore from Cape May Point to Sea Breeze. Luckily, we had a head-start based on a preliminary census survey from 2021 that documented some already existing pairs as well as some sites with potentially suitable nesting habitat. We were also fortunate to have a dedicated seasonal technician assisting with the heavy workload. That said, figuring out how to access many of these sites was definitely a learning curve. We quickly discovered that many beaches were only reachable by boat or kayak and only during a narrow window of tide and wind conditions. Other sites were walkable, but only at peak low tides, which meant our surveys couldn’t take too long without risking becoming stranded by the rising tide.
CWFNJ’s 2022 Edwin B. Forsythe NWR Beach Nesting Bird Field Crew. L to R: Jacob Miranda, Lexie Lawson, Amy Kopec, Erin Foley, (missing Dakota Bell).
For the past eight years, CWF has been contracted by the U.S. Fish and Wildlife Service through a cooperative agreement to provide monitoring and management of beach nesting birds at the Edwin B. Forsythe National Wildlife Refuge. The Refuge nesting sites – both the Holgate and Little Beach Island Units – provide some of the only habitat in the state closed to the public and free of human disturbance and detrimental beach management practices. The habitat at the sites is especially suitable for the state endangered piping plover as a result of optimal nesting conditions created by Superstorm Sandy and largely sustained since then through winter storms. As of the 2021 season, the Refuge sites had the highest concentration of piping plovers in the state, with Holgate having by far the most pairs (46). Furthermore, on average in recent years, Holgate has produced a higher fledgling rate than many sites in the state.
Most people are surprised to hear that American oystercatchers are present in New Jersey in the winter. They usually associate the charismatic shorebird as a breeding species here. Our state’s wintering oystercatchers, a combination of breeders from further north and our own, are at the northern extent of the Atlantic coast wintering range.
American oystercatcher foraging for oysters along the Delaware Bay. Photo credit: Meghan Kolk.
The Delaware Bay is well known for the spectacular phenomenon of spawning horseshoe crabs and migrating red knots every May, but in recent years the American oystercatchers (Haematopus palliatus) have also discovered the allure of the Bayshore and made it their home. American oystercatchers, a State Species of Special Concern, have been monitored and managed by CWF and the NJDFW’s Endangered and Non-game Species Program along the Atlantic coast beaches for nearly two decades, resulting in a steady population increase. However, the population that breeds along the Bayshore, first documented in 2016, has not received the same attention and had never been fully surveyed until this year.
CWF’s interest in this newly discovered population led to a small pilot study of a few known breeding pairs in 2018. Then this past May, we launched a bay-wide survey of the sandy beaches of the New Jersey side of the Bay from Cape May Point up to Seabreeze, the northernmost beach in Cumberland County. The purpose of the bay-wide survey is to determine a baseline of the number and distribution of breeding pairs along the Bayshore. The data gathered from this survey will add to the Statewide population estimate and help determine the amount of time and funding needed to fully monitor and manage the Bay’s population. More monitoring will be necessary to assess risk factors and reproductive success. Reproductive success can then be maximized by managing for risk factors such human disturbance, predation and tidal flooding.
This survey was made possible due to the efforts of dedicated volunteers and could not have been completed without their help. Unlike the Atlantic coast, the Bayshore beaches are often difficult to access, and many can only be reached by boat, making this survey more challenging. In fact, two sites that we planned to survey proved to be too difficult to reach and were skipped for this year. Each of the 33 remaining sites were surveyed just once within a specific timeframe, giving only a snapshot of the breeding season. We hope to be able to collect much more information in the future when more funding for this project is available. Based on the survey that was conducted, 13 pairs were documented at 8 different sites and 8 nests were documented at 5 different sites.
In addition to the formal survey, I was able to collect some observations as I spent every day in May on the Bay working with red knots. I took notice of the prey items that the oystercatchers were choosing. I often observed them feasting on oysters, which were plucked off exposed rubble at low tide. They also spent time at the man-made oyster reefs that were constructed at several beaches to act as breakwaters to slow the erosion of beaches. They also favored ribbed mussel beds, which become exposed as the tide recedes. The most interesting foraging behavior I witnessed was an oystercatcher plucking a fresh slipper shell off a horseshoe crab as it came to shore to spawn. It seems the Bay offers a variety of good food sources for a bird that mainly preys on bivalve mollusks.
I also noticed that flocks of up to 11 oystercatchers were traveling together up and down the Bayshore. This is a peculiar behavior since oystercatchers are highly territorial during the breeding season and are typically only seen in flocks once the breeding season is over. Could it be that the Bayshore is a popular spot for non-breeding young adults to hang out?
So much more research is needed to answer the many questions we have about the mysterious Bayshore oystercatchers.
