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.
Tag: migration
Happy Amphibian Week!
by Christine Healy, Wildlife Biologist
If you follow us or any other wildlife organizations on social media, you may have noticed that our posts these last few days have been inundated with amphibians. It may seem like odd timing, given that our early breeders (wood frogs, spotted, and Jefferson salamanders) completed their crossroad migration last month. But the reason is simple – it’s Amphibian Week!
Globally, amphibians are disappearing faster than any other vertebrate group. The International Union for the Conservation of Nature (IUCN) estimates that 41% of amphibian species categorized for their Red List are currently facing extinction. That estimate is likely conservative, given that these creatures are often small and difficult to survey, rendering many species data deficient. This is concerning from multiple perspectives. From an ethical standpoint, we don’t want any wildlife to go extinct except maybe, in my extremely biased opinion, certain types of ticks… (I began my career as a moose technician and saw firsthand the terrible consequences that winter ticks have on these behemoths). Beyond that though, amphibians are tasked with a lot of responsibilities and carry out their work efficiently and without complaint. The list is inexhaustive but here are a few things that amphibians are doing for us and our planet as we speak: filtering water, sequestering carbon, eating pests (like mosquitos!), serving as prey for countless predators, helping researchers study regeneration (with hopeful applications to the future of organ transplants), aerating the soil in your garden, indicating where water sources have been contaminated by pollutants, and giving everyone who meets them a reason to smile.
Continue reading “Happy Amphibian Week!”CWF Book Club: Winter Reading List
Meaghan’s Recommendations
by Meaghan Lyon, Wildlife Biologist
The cold and dreary winter weather makes for the perfect excuse to curl up with a book. Reading a good book can transport you into new worlds, or, in the case of the following books I’m about to recommend, help you get excited about getting outside to explore your own winter wildland.
My first recommendation is a Field Guide, Tracking and the Art of Seeing: How to Read Animal Tracks and Sign written by Paul Rezendes. Although this is a field guide to tracking wildlife, this book includes personal accounts that make it much more readable cover to cover. The author includes several North American species including rodents, hoofed animals, bears, raccoons, opossums, and members of the weasel, rabbit, dog, and cat families. He describes not only the signs these animals leave but also their ways of life throughout the seasons to help the reader get a fuller picture.
Continue reading “CWF Book Club: Winter Reading List”The Mighty Migration of the Magnificent Monarch
by Mary Emich, Assistant Biologist
Over the last decade, the monarch butterfly, Danaus plexippus, population has declined. Climate change has affected weather conditions, the winters are colder and wetter while the summers are hot and drier. This disturbs their survival rate, especially during their long annual migration. Other factors like pesticides and a loss of habitat to human development further threaten the monarch population.
The monarch butterfly migration is mysterious and magnificent. Every fall season, monarch butterflies travel thousands of miles from their breeding grounds in the United States and Canada to escape the cold winters. Monarchs in Eastern North America spend the winter months in the Transverse Neo-Volcanic Mountain Range in Michoacan, Mexico. To reach their destination, monarch butterflies migrate over 3,000 miles, utilizing the air currents and making many stops along the way.
Continue reading “The Mighty Migration of the Magnificent Monarch”Red knot decline confirmed by CWF research highlighted in NY Times
Conserve Wildlife Foundation’s research with scientist Dr. Larry Niles was highlighted in today’s New York Times feature detailing the 80 percent decline in red knots in New Jersey’s Delaware Bay this spring.
by Jon Hurdle, The New York Times
A sudden drop in the number of red knots visiting the beaches of Delaware Bay during migration this spring has renewed concern among scientists about the survival of the threatened shore bird’s Atlantic Coast population.
According to biologists, the number of knots that stayed to feed at the bay in May declined by about 80 percent from the same time last year. The Delaware Bay is one of the world’s most important sites for shorebird migration.
CWF live interview with PBS Nature explores climate change impacts on birds
The WNET-PBS Nature program Peril & Promise celebrated the Great Backyard Bird Count with two live interviews with Conserve Wildlife Foundation at DeKorte Park in the Meadowlands.
In the first live interview, CWF Executive Director David Wheeler and Jim Wright, who has written widely about birds and the Meadowlands, discussed the importance of bird counts to CWF’s work, and the growing threat of climate change on bird populations around the world.
Climate change is “toughest on the migrants,” said Wheeler. “When you think about a bird leaving its neotropical wintering grounds in Central or South America and then coming up to New York or New Jersey, that’s a leap of faith that everything is as it has always been. But in reality, as spring seems to arrive earlier each year along with the leaves, the foliage, the insects, basically the bird risks coming back to a depleted prey resource – and they can struggle to survive.”
View the interview here. Check our blog again tomorrow for the second interview, discussing the remarkable recovery of bald eagles.
Peril & Promise: The Challenge of Climate Change is a public media initiative from WNET in New York reporting on the human stories of climate change.
Richard W. DeKorte Park is a nationally recognized birding hotspot along the Atlantic Flyway with 3.5 miles of walking trails in the shadow of the Manhattan skyline, part of the Meadowlands region where over 285 bird species have been identified. It is managed by the New Jersey Sports and Exposition Authority.
Shorebirds lift off to an uncertain end from Delaware Bay
By Dr. Larry Niles, LJ Niles Associates, LLC
I am reviewing a new paper by Sjoerd Duijns, a student working on the benefits of being a fat shorebird. Still, a draft, the paper analyses data from radio-tagged red knots leaving the Bay in good condition (i.e. fat) and finds they may leave later from Delaware Bay than lighter birds but arrive earlier in the breeding grounds because they can pick the best time to leave. They are also more likely to breed successfully and survive the Arctic breeding season to the following fall. In other words, being a fat knot on Delaware Bay makes life good.
So, in light of this new information, how did the red knots and other shorebirds fare in this year’s Delaware Bay Stopover? One must not be firm, with so many unknowns, but here’s a working biologist’s best guess.
By all accounts it was one of the worst years in recent memory, but with a twist that offers a glimmer of hope.
First, the Bay’s water reflected an unusually cool May and never really warmed to the levels necessary for a really good horseshoe crab spawn until the very end. This caused odd occurrences of crab spawning. For example, crabs bred in greater densities at the southern beaches this year, more than in previous years. The spawn at Norburys Landing, just south of the commercial oyster aquaculture development zone (ADZ), was one of the best this year, and knots and other shorebirds used the area in great number. One can only guess the water temperatures warmed over the wide inter-tidal flats provided just enough to elicit spawning. The same process was true of all the creeks on the Bay.
Second, the knot numbers never really climbed to the levels of the last three years. I’m guessing this was illusory, a consequence of the count being done on two days at the peak. It’s likely many more birds came to the Bay and seeing many birds for too few eggs, left for better resources elsewhere. Those that left were probably short distance winterers – those from relatively close in Florida and other nearby areas. The Bay’s horseshoe crab eggs would help them too, but they can get by on Atlantic Coast clams and mussels. The long-distance birds are the ones that need the Bay’s resources.
Third, when finally, the spawn got underway, a freak concurrence of wind and tide killed many thousands of crabs, potentially damaging the population and very likely ending any possibility of a really great spawn. The cobblestone road of crabs on the water’s edge. We saw none of that this year. Not once.
Grim results, but here’s the twist. In good years, knots leave near the 27th of May. One day they jam the beach gobbling up eggs, the next day there gone. In bad years, they linger. In 2003, we caught birds on the June 10th. There’s a cost to this of course, in lower survival and failing production. This year was a new in between. By the time of departure on May 27th, less than a quarter of the knots were prepared to leave. But they hung on until the 30th, blessed with a new flush of horseshoe crab eggs created by a middling spawn and a northwesterly wind churning up the beaches and exposing deeply buried eggs. Did the birds gain enough weight?
It’s hard to say, our last catch of just 33 knots suggests they might have, but an end-of-the-season catch makes a poor assessment. Once birds start leaving, the ones behind could be the light birds not ready to leave, or the heavy birds waiting for better weather. We won’t really know until the fall counts in the southbound stopover or the winter count in Tierra del Fuego.
This, our 21st season of intense research and conservation on Delaware Bay by all accounts will be like no other. Throughout all of it, the team of scientists and volunteers remained inspired, energetic and resourceful. In this one month, we conducted more scientific investigation and conservation than most projects do in an entire year. Whatever the outcome of this year’s stopover season, our team can look hopefully to the north and know that all that could be done for the birds was done.
Those of us that were paid for our time sincerely thank those who volunteered their time including; the stewards that manned the closed beaches helping hundreds of people understand why closures were needed; the volunteers in the banding team who endured long hours of preparing equipment, making bands, sewing nets and keeping cages and of course counting, catching and processing birds; the volunteers who doggedly pursue opportunities to resight flagged birds to estimate numbers and yearly survival; the volunteers that provided meals every single night, a welcome relief from a hard day’s work; and finally, the volunteers that went out all over the Bay to save horseshoe crabs in weather both good and bad. We all did our best. God help the birds and horseshoe crabs.
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
LEARN MORE
- Delaware Bay Shorebird Project
- 2017 Delaware Bay Shorebird Project blogs
- 2016 Delaware Bay Shorebird Project blogs
Scarcity and Abundant – Shorebirds Near the Finish Line on the Delaware Bay
By Dr. Larry Niles, LJ Niles Associates, LLC
Our latest catch of red knots and ruddy turnstones two days ago (May 27) suggests 2017 to be one of the most challenging years for our 20 years of work on Delaware Bay. It challenged the birds for certain.
For example, as of two days ago (May 27), the average weights of red knots remain mired in the mid 160’s when it should be in the 180-gram range. This seems a minor difference but to red knots it means a flight through the cold and often inhospitable north country of Canada and dropping out of the sky never to be seen again or landing and never attempting to breed. We really don’t know for sure what happens to ill-prepared shorebirds, except they are less likely to be seen ever again. In 2017 most birds will be ill prepared.
This season also challenged our understanding because it lies so far outside the norm. To be sure the cause of this dramatic scarcity of horseshoe crab eggs springs from the cold weather this May. We started with a good crab spawn in the first week of May, when water temperatures rose somewhat faster than normal, a consequence no doubt of one of the warmest winters on record. Then cold and wet weather dogged the Bayshore until the day of this post. Today, temperatures will rise no higher than 70 degrees Fahrenheit and the prospects for warmer weather are unlikely for the rest of the week. The cold air temperatures forced down the bay temperature in the second week and although it has gradually improved it is still low by normal standards.
All of this led to generally diminished horseshoe crab eggs especially on the beaches, the mainstay of most stopovers of the past. This year crabs mostly spawned in the creek mouth and outer creeks shoals, mostly spurred to spawn by tidal waters warmed by the movement in and out of the small estuarine systems. Water moves in with the tide and out again to the creek mouths twice a day warming the shoals.
The Importance of Tidal Creek Mouths and Shoals
The creeks also accumulate sand leaving them loose and perfect for crab spawning. Even in good years, egg densities in the creeks top all beaches, no matter where they occur. The sands of the shoals loosen by the waves of the Bay and release more buried eggs than those buried in the beaches, making more available to the birds. The creek mouths on the Cape May peninsula from Green Creek to Moores Creek saved the birds from an even worse fate this year and the best were those that benefited from the restoration of Reeds, Cooks, Kimbles and Pierce Point Beaches. As it happens a major portion of the Bay’s knots stayed in this area throughout the entire month but flying widely in search of pockets of good spawning in other places. This year Norbury’s in the south and Goshen in the north stood out, and extended the core stopover area.
Spawning Starts Again
Then in the last three days all changed. The new moon tides, reaching around 8 feet for four nights in a row, spurred spawning despite the relatively cool water. Today, May 29, the crabs shifted into high gear.
It takes a lot of crabs breeding to bring eggs to the surface on the beaches, there must be enough breeding for one crab to dig up the eggs of another. For the first time, this occurred in the last few night and we finally saw green eggs on the sand. A welcoming sight for the birds, who could barely stand still and gobble up the fat producing eggs. With most of these Arctic nesting shorebirds remaining in the Bay and apparently feeding right into the night, they still might reach the fat gain finish line and only lose a few days reaching the Arctic. The next few days will tell.
Can they though? A good question and just one of the many that have challenged our team’s knowledge of this well-known stopover. With literally centuries of combined experience (many of our team, including this author, are long in the tooth as the Brits would say) we still kept guessing what would happen next throughout the season. Would the birds suffer mighty declines as a consequence of the generally diminished spawn of horseshoe crabs? Or will they build weight in time to get to the Arctic in good condition? This is usually the central question.
Why Are There Fewer Knots?
An equally intriguing question, however, is why have red knot numbers in Delaware Bay declined this year? We estimate shorebird numbers in two ways, direct observation by aerial and ground counts and a statistically derived estimate based on the resighting of birds flagged with unique IDs. Our aerial and ground counts tell us how one year compares to another because we have been doing shorebirds counts by airplane, boat and on the ground since 1981. This year the number fell dramatically.
At the start of our project on Delaware Bay in 1986, we had nearly 100,000 knots on the Bay and nearly 1.5 million shorebirds of all species. The number of knots declined to around 15,000 in the mid-2000’s, then jumped to over 24,000 over the last four years. This year our best estimate is around 17,969, a 5,000-bird decline. Why did this happen?
One must always consider the possibility of a large group of birds dying. But this is not likely.
More likely, some portion of the knot flock came to the Bay, and on finding too few eggs or too much competition, moved on to better places. The ones moving on could have been the short distance migrants, those who spent their winter in Southeast US or the Caribbean. These birds travel a shorter distance and so have a longer time and lower energy needs than those that winter in South America. These long-distance migrants would have a very difficult time gaining weight on anything other than crab eggs (I explained this in a previous post). There are two reasons to believe the short distance birds moved on from the Bay this year.
The first is the discovery of birds banded in Delaware Bay this year and reported elsewhere. I reported on Mark Faherty’s Ebird report of a knot he saw in Cape Cod, that was flagged by the Delaware Bay Shorebird Team on May 16, 2017. The second line of evidence is the 1,300 birds seen by our team feeding on a 10-mile stretch of the Atlantic Coast marsh from Cape May to Stone Harbor. Play this out over the entire coast of New Jersey and other places with sand and marsh, like Cape Cod, and one could easily imagine 5,000 knots using other places.
But this reduction in population also suggests an explanation for the sudden rise in numbers found in 2013. Did the restoration of habitat on the Delaware Bay coast bring back knots that once used the Bay but stopped because of the lack of available eggs? In other words, did the increase in numbers seen in the Bay reflect a return of birds and not a population increase? This year’s loss may simply be a result of those returning birds, leaving once again.
Let’s hope so. At any rate, eggs are now available to all birds in the Bay and we should start seeing them leave for the Arctic. Let’s hope for that too.
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
LEARN MORE
- Delaware Bay Shorebird Project
- 2017 Delaware Bay Shorebird Project blogs
- 2016 Delaware Bay Shorebird Project blogs
In Dangerous Territory on the Delaware Bay
By Dr. Larry Niles, LJ Niles Associates, LLC
Four days ago, the shorebirds of Delaware Bay could look forward to a bright future. But in the last week their chances for survival and good production have diminished. In fact, they are as dismal as the cold drizzle pockmarking the murky water in front of our house on Reeds Beach.
The following two graphs tell the story. We captured red knots on May 12 and 16 that showed a normal, although not spectacular progression. Then we made a catch of knots on the 19th and again today on the 23rd, and in total they gained only 2 grams of fat per day. With an average weight of 144 grams at this late date and only 7 days to go before they must leave for the Arctic, their future looks bleak. If current conditions hold, the knots will suffer their worst year in 14 years. Turnstones fared no better gaining less than a gram per day on average.
So why this dismal report? Several factors are at work that were covered in my last post. The water temperature of the bay has only just exceeded the threshold for horseshoe crabs to start breeding in earnest. But the nights are cold and the water temperature remains cold. Last night was the first good crab spawn since the birds arrived and it was lackluster. Although there is some spawning in the creek mouth shoals and the lower beaches near Norburys Landing and Villas, our most productive beaches remain nearly devoid of crabs and crab eggs.
The second problem is still a mystery. At this stage only about half of the red knots have found their way into the bay. Weather patterns in the southern US could have been blocking migration for the last 5 days because adverse winds, poor visibility and rain impedes birds progress and could stop northward movement. The conditions have finally let up, so it possible a new cohort of birds might arrive any day. If so they will face a true food fight with many birds already here and desperate for eggs.
However, it may not be the adverse weather but choice that is keeping the population down. Today we learned of a red knot banded on May 16 this year by our counterparts in Delaware that was resighted in Cape Cod by Mark Faherty, the senior scientist for Massachusetts Audubon in Cape Cod. In other words, red knots and other shorebirds are coming to the bay finding too little food or too much competition for the food now available and choose to move on. This is very possible for the short distance migrants because they arrive earlier and have less weight to gain before leaving for the Arctic. Knots wintering in Tierra del Fuego, arrive later and in much worse condition, often times lose muscle mass to get here. They cannot recover that loss and still gain an extra 80 grams on their normal diet of mussels and clams.
We tried to test this second possibility today (May 23) after our red knot catch this morning. Humphrey Sitters, Amanda Dey and I surveyed the intertidal mud flats of the Atlantic Coast from Cape May to Stone Harbor looking closely at the mussel beds. We know that every year red knots, especially short distance birds, use mussels and to some extent clams, rather than come to the bay and feast on horseshoe crab eggs – simply because they can. We found 1700 knots, so it possible even more are spread out further up and down the coast.
In the end, it may turn out to be both explanations. The short distance knots are using the Atlantic Coast and the long-distance birds have yet to arrive. One should remember that the knot is federally listed in both Canada and the US primarily because of the dramatic declines in the long-distance winters. There is still a small window for a successful outcome. The next few days will tell the full story.
Dr. Larry Niles has led efforts to protect red knots and horseshoe crabs for over 30 years.
LEARN MORE
- Delaware Bay Shorebird Project
- 2017 Delaware Bay Shorebird Project blogs
- 2016 Delaware Bay Shorebird Project blogs
New Jersey’s Key Role in the Monarch Migration
The Garden State annually hosts swarms of southbound Monarch Butterflies
By: Kendall Miller, Project Coordinator
Monarch has been a conservation buzz-word for the past decade when data revealed that the population had appeared to be on the decline. Then in 2013, the population of wintering monarch butterflies in Mexico reached an all-time low that jolted scientists, environmentalists, and enthusiasts across the nation.
This marvelous and iconic lepidopteran is found throughout the continental United States. Its 3,000 mile long migration is an amazing natural phenomenon. The news of population declines in Mexican wintering sites inflamed concern and incited action. Many groups have since created partnerships, implemented programs, and conducted research to understand more about this widely known yet still mysterious insect.
The location of wintering monarchs was a complete mystery until 1975 when the remote wintering sites were discovered in transvolcanic mountain ranges in Mexico. Much is still to be discovered about the migration pathways even within the United States, and doing so will answer questions which will inform conservation and management of this species which faces multiple threats during every aspect of its expansive journey.
Glider pilots have observed monarch butterflies at an altitude of 1200 meters (Gibo 1981). Migratory flights at these altitudes can allow insects to disperse against wind directions found at lower altitudes.
But first, a little bit about biology and the annual life cycle
The monarch’s annual lifecycle is a really marvelous and multifaceted journey – it can be thought of as a multigenerational relay race.
Monarch butterflies, just like other lepidopterans, metamorphosis from caterpillar to butterfly. The big thing that sets them apart is the migration they make annually. (Although there are many other species of moths and butterflies, and other insects as well that migrate – the monarch is arguably the most well recognized example http://texasento.net/migration.htm).
Temporal cues and an innate determination drive these ambitions fliers to travel as far north as the Canadian border. In the search for milkweed and favorable temperatures – possibly to avoid disease pressures – monarchs fly north to reproduce and recolonize across North America each year.
They leave overwintering grounds in Mexico in early spring. Along their route the monarchs will mate and reproduce. Their lives are lived within a short couple weeks, and their offspring will continue the migration northwards in search of food and milkweed.
When the seasons shift in late summer and early fall, the last generation of monarchs will begin a southbound journey, instinctively traveling to wintering sites in Mexico (there are a few populations that overwinter in California and Florida – but the large majority are thought to return to Mexico). This generation will be responsible for making the longest trek of the migration to wintering grounds. These monarchs enter reproductive diapause – the state where the body will temporarily pause reproduction – until the following spring. These monarchs will spend the winter roosting in trees in Mexico until spring when they will take up the first leg of the relay north.
This last generation from the previous year now makes up the first generation of the present year – and will pass the baton on to their offspring as the cycle starts anew.
The role of the Garden State
So what part does New Jersey play in the grand scheme of this massive population?
The Atlantic coast migration was once characterized as “aberrant”, a fluke of sorts – the result of southbound monarchs being blown off course. Research and monitoring conducted in Cape May and published by Walton and Brower (1996) in The Journal of the Lepidopterist’s Society have supported the hypothesis that a migration along the Atlantic coast is part of the monarch’s normal fall migration.
What does a monarch have in common with a hawk?
Walton and Brower (1996) have proposed the idea that monarch butterflies could display similar flight patterns to that of migrating hawks. Utilizing an elliptical flight path during the fall south-bound migration, the model suggests that these birds take advantage of prevailing winds by first traveling east and then west, thus providing a quicker and more energetically-efficient route. Could monarch do the same?
New Jersey – Southern New Jersey and Cape May in particular – is historically recognized as a concentration area for southbound monarchs during the fall migration to wintering grounds. Hamilton (1885) [expressed his wonder of the] characterized the September 1885 monarch migration at Brigantine, New Jersey as “almost past belief … millions is but feebly expressive … miles of them is no exaggeration.” Reports of trees “more orange than green” is no exaggeration, as monarchs congregate en masse in prime roosting spots to warm and rest.
But why is this important? The monarchs migrating through Cape May seem to be representative of the entire North Eastern population – and therefore it offers the opportunity to collect quantitative data on populations in addition to other annual counts. The fourth of July counts focus on quantitatively monitoring the Northeastern population of monarchs as they arrive in the spring and summer. Therefore this data can be used to analyze population trends.
What part can New Jersey residents play?
Monarchs are traveling across New Jersey May through October. There are plenty of simple ways you can help protect this iconic species.
- Plant native species of flowering plants – monarchs and other insects (like bees) rely on a healthy diversity of nectar sources. Planting a wildflower garden is a quaint, ecological-friendly way to create habitat, and not to mention, make less work watering and money spent purchasing plants. Check out the Native Plant Society or Jersey Friendly Yards to get started. http://npsnj.org/ http://www.jerseyyards.org/
- Share this article, talk about environmental issues, and get informed. Show your support and share your concern for the wellbeing of this (and other) species!
- Rear monarchs. At home or in classrooms, rearing wild monarchs and releasing them is a rewarding and educational way to contribute.
- Participate in tagging and monitoring projects. Monitoring and tagging projects take place in the summer and fall for New Jersey Monarchs. You can also contribute simply by reporting your sightings on these websites.
- Report sightings and tag monarchs with Monarch Watch.
- Be a Citizen Scientist by participating in the Journey North mapping and monitoring project by reporting sightings.
- In Cape May, the Cape May Monarch Monitoring Project conducts fall migration censuses each year.
- The North American Butterfly Association is responsible for the Fourth of July butterfly count census.
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