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 best news is a direct consequence of these good conditions, the number of knots and turnstones increased this year. Our season-high estimates show that there are 34,500 knots in the bay and 21,000 ruddy turnstones. These may be the highest counts on the bay in at least 15 years.
Why? At first one would conclude the increased numbers on the bay represent a real increase in the size of the population, but it is not. Shorebirds need time to respond to improving conditions because they are relatively slow breeders, as are most Arctic breeders. Knot numbers on Delaware Bay basically depend on the availability of crab eggs. In bad years, numbers go down because birds come to the bay and leave quickly. Continue reading “Good horseshoe crab egg densities draw 34,500 Red Knots to the bay”
The horseshoe crabs extended their breeding period into the neap tide phase after the cold weather of mid-May decreased water temperature during the spring tides. The crabs roughly require a water temperature of about 59 degrees F before breeding begins in earnest. Crabs still breed at a lower temperature, but many more will breed above the temperature threshold.
At the same time, crabs also look for spring tides, the higher high tides that come with full and new moons, because they can breed in sandy places unavailable at lower tides. This year the water cooled during the new moon spring tide and warmed in the neap. Good spawning during the neap tides of the last week was welcome good news. This May good spawning conditions will raise average egg densities about 50% higher than last year. Continue reading “Horseshoe crabs expanded breeding into neap tides”
Just above and to the right of the plane shadow, thousands of shorebirds gather. Photo by Joe Smith
CWF scientists recently returned from a trip to Tierra del Fuego where they studied red knots and other migratory shorebirds that spend the month of May at New Jersey’s Delaware Bayshore.
CWF consultant Joe Smith captured some incredible aerial images of the coastline holding a flock of thousands of shorebirds in his blog story. See more photos of the flock and read Joe’s introductory overview about the trip here. Stay tuned for more installments about this vital trip.
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.
As part of the Beach Nesting Birds team last season, I had grown accustomed to scouring the beach daily for signs of birds: tracks, scrapes, nests and eventually adorable chicks. On my free time, my beach walks are spent combing the beach for various treasures. Yesterday, I had a new reason to walk the beach and I had to re-train my focus to something that never caught my interest before. It was my first survey for the endangered beach plant, seabeach amaranth (Amaranthus pumilus). Continue reading “Beach Plants Need Love, Too”
Many piping plover and American oystercatcher pairs have been busy laying their eggs over the last few weeks. As beach nesting bird biologists, we invest a lot of time into every pair at our sites. We revel in their successes and feel defeated at their losses. Unfortunately, many nests did not fare well in the April 25th Nor’easter that was coupled with new moon tides. Luckily, it is early enough in the season that all of them have begun, or will soon begin, attempting new nests.
The breeding habitat of the American oystercatcher in New Jersey consists of coastal beaches, inlet systems, and salt marshes. Population estimates in New Jersey suggest 350-400 breeding pairs can be found here from March through August. Much of the monitoring and research done with American oystercatchers in New Jersey takes place on the coastal beaches where other beach nesting birds, such as piping plovers, least terns and black skimmers, are found. In 2016, more than 120 breeding pairs of beach nesting American oystercatchers successfully fledged 83 chicks. This was an especially productive year for those pairs and productivity levels were well above the target goal of .5 chicks per pair.
Photo courtesy of Sam Galick.
Oystercatchers arrive back on their breeding grounds here in New Jersey in early March to set up breeding territories and begin nesting. Once paired up, adults typically lay one to three eggs. Both the male and female will take turns incubating the nest for 28 days. Once chicks hatch, they are semi-precocial, which means they are born in an advanced state, but are still reliant on adults for food and protection. Oystercatcher chicks are fledged (or able to fly) 35 days after hatching. After fledging, most Oystercatchers migrate to the southeast, but a wintering population does remain here in New Jersey.
American oystercatchers are listed as a Species of Special Concern in New Jersey. A “Species of Special Concern” is a status determined by the New Jersey Division of Fish & Wildlife and applies to species that have an inherent threat to their population or have evidence of recent population declines. Since American oystercatchers share the same habitat as other endangered or threatened beach nesting birds (piping plovers, least terns, and black skimmers), they also share the same threats to their nests and young. Human disturbance, a host of predators, and flooding events, such as the one that took place last week, are just some of the many threats beach nesting birds face daily.
The Conserve Wildlife Foundation of New Jersey has long partnered with the New Jersey Division of Fish and Wildlife’s Endangered and Nongame Species program in the monitoring and management of New Jersey’s endangered beach nesting birds. Fencing and signage are placed in nesting areas to alert beachgoers to the presence of nesting American oystercatchers and other beach nesting birds. Throughout the summer, CWFNJ and partners will be out on the beaches monitoring and collecting data that will be used to track population trends and identify threats to oystercatchers and their young.
Emily Heiser is a wildlife biologist for Conserve Wildlife Foundation of New Jersey.
NEW, WEEKLY UPDATES FROM NEW JERSEY’S BEACH NESTING BIRD PROJECT TEAM
by Todd Pover, Beach Nesting Bird Project Manager
There are many ways to gauge success for our beachnesting bird project. We look at how well our management tools work, the effectiveness of our partnerships, and how well our educational efforts work, to name a few qualitative measures we use. At some point, however, it comes down to cold hard numbers, how well did the birds do in a particular season and over the long-term. We are at that point in the season, and for the most part, I am happy to report it has been an excellent breeding year. I will caution that these are still preliminary figures, some quality checking of the data needs to be done before they are final, but the trends are clear.
One of a “bumper crop” of piping plover fledglings produced in New Jersey in 2016. Photo courtesy of Kevin Knutsen.
First up are piping plovers. We will come in at ~115 pairs statewide, up modestly from the 108 pairs in 2015, and the second consecutive year of an increase after hitting our historic low of just 92 pairs in 2014. So, we have climbed back closer to our long-term average, but there is still room to improve. The really good news is our productivity this year – close to a statewide record at 1.37 chicks fledged per pairs – puts us in the position to continue our population increase. If trends hold, because piping plovers demonstrate high site (or region) fidelity, when we produce a lot of fledglings, our breeding population rises in the next year or two. With three straight years of well above average fledgling rates for New Jersey now in the books, our prospects look good in the short term for our breeding population levels.
Least terns and black skimmers, which nest in colonies, sometimes numbering hundreds (or even thousands), are more challenging to count and assess, but we had at least modest success this year for both species. As is typical, our least tern colonies were variable, with some completely failing and others being highly productive. The Monmouth County region, one of our strongholds for least terns in New Jersey, didn’t have one colony that was a standout but most of them had at least some success. In South Jersey, our two largest colonies at Holgate (EB Forsythe NWR) and Seaview Harbor were very successful and helped make up for losses and failures at other colonies. The majority of our state’s black skimmers are concentrated in one large colony at Seaview Harbor, and although skimmers are our latest nesters (so the season isn’t quite over for them), they appear to have been very successful there, which means a good season overall for the state.
We also track American oystercatchers, although only for the portion that nest on the barrier beaches and spits. Because the biggest percentage of oystercatchers in the state nest on back bay and marsh islands, we cannot determine true statewide population or productivity levels, but the population on the beach habitat appears to be rising in recent years. Typically breeding success is lower for oystercatchers on the beach habitat due to high levels of human disturbance and predators, but productivity has been relative high the past two years. Of particular note this year was Stone Harbor Point, where a record number of 27 pairs nested and produced over 30 fledglings.
The reality is our beachnester staff works just as hard in years when the birds do poorly, as when they do well like this year, but it is SO much more rewarding when we have a good season. So as we wrap up the season, we are all feeling in a bit of a celebratory mode now!
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.
