Ospreys Have A Shocking Spring Migration!
Written by Jenna Reynolds, President/Director of Save Coastal Wildlife
Can you feel it? Spring is underway in the northern hemisphere. The first full day of spring, a season normally full of hope and renewal, arrives around March 20.
Just like clockwork, ospreys (Pandion haliaetus), a species listed as threatened in New Jersey under the Endangered and Nongame Species Conservation Act of 1973, return every spring from over-wintering sites in the tropics to watery areas up north, including rivers, lakes, and the world famous Jersey Shore, to begin another busy breeding season raising a feathered family. Because of a long breeding cycle (they are big birds of course), ospreys are among the first birds to migrate north from the tropics to start nesting.
The reappearance of ospreys every spring is one of the great natural wonders to watch for along the Jersey Shore. Forget about looking for robins or even red-winged blackbirds, both of these birds are often year-round residents or short-distance migrants. The first sight of a long-distance osprey is a true sign of spring!
The fun usually begins in early March when wildlife watchers and birders from all over the state try to spot the first osprey of the season. People are out and about in search of the bird up and down the Jersey Shore, from Raritan Bay down to Delaware Bay.
Ospreys are found on all continents except Antarctica, and always located near water. Depending on where you go, people may call them sea hawks, river hawks or fish hawks. Ospreys are large fish-eating raptors ranging in size from 20-24 inches (50-60 centimeters) long with a wingspan of 5 to 5 ½ (1.5-1.7 meters) feet. They have dense dark brown-and-white wings, a large hooked beak and prominent large yellow eyes in adults, which provide sharpened eyesight at three to five times the distance that humans can see. An osprey is able to spot a fish about two hundred feet away.
The bird’s most noticeable feature is the black band of feathers that span from its eyes and around its head resembling a bandit’s mask or the mask worn by that iconic “masked man” known as the Lone Ranger, which is remarkable because ospreys always migrate and forage for food as individuals, not in flocks.
Odds are good you have seen this bird or its nest around the Jersey Shore during spring, summer or fall. An osprey’s nest tends to be a pile of sticks and branches haphazardly assembled atop a 20-foot tall artificial nesting platform, a tall dead tree, a buoy, or some other structure near or in the water.
An osprey atop a nesting platform located near the Mullica River, New Jersey.
A quick glance at this bird may appear like seeing a large gull. But ospreys are no gull! They’re not even related to gulls. In fact, they are unlike any raptors.
Ospreys are a very special type of bird of prey that is a superb angler. While many other birds of prey hunt for birds, mammals, or any live land animal, or even the carcass of an already-dead animal, ospreys go where few hawks dare – into the water to fish for food. Ospreys are the only raptor that relies so much on fishing for a living.
According to the Cornell Lab of Ornithology, ospreys can catch a fish at least one in every four dives, with success rates sometimes as high as 70 percent. The average time a bird spends searching for a fish before making a catch is about 12 minutes. A much better success rate than most weekend warriors along the Jersey Shore that try their luck at catching a fish with a rod and reel. Even bald eagles, another raptor that loves eating fish, are not as good at catching a fishy meal as an osprey, which is probably why sometimes rather than doing their own hunting a bald eagle will harass an osprey, making it drop a fish or even steal their fish out of their talons. As Benjamin Franklin declared in his writings of 1784, a bald eagle is “too lazy to fish for himself…and does not get his living honestly.” Words that are true today as they were in the 18th century.
Most avian field guides indicate that 99 percent of an osprey’s diet consists of live fish, including menhaden or bunker, flounder and bluefish. With long legs that are largely bare of feathers, strong needle sharped curved talons, and a special reversible outer toe that swings back to help hold a fish, ospreys have evolved over time to dive into the water from heights of up to 100 feet to catch fish like no other hawk. This is why the osprey is the only member of its family, Pandionidae, there is no other bird like an osprey.
An adult osprey with a newly caught menhaden in its talons
An osprey eating the insides of a fish
One of the most stressful times for any bird, including an osprey is spring migration. When people observe ospreys for the first time every spring they often see birds that appear ragged, starved and exhausted. The fish hawks have just completed a challenging northward marathon migration flying thousands of miles in most cases nearly nonstop into storms, high winds, and through hazardous situations all the way from South America to North America.
Spring migration for ospreys is an extraordinary journey that we are still trying to understand, though it’s slowly getting better. A 2001 journal article in The Condor by Mark S. Martell and others tell us that the sightings and returns from metal bands put around the legs of ospreys for the past 50 years have confirmed that spring migrations are quicker than fall migrations. Ospreys spend proportionally more time traveling than stopping to rest and eat during spring migration. No doubt the need to breed is strong in these birds.
When we put this data together with information from improving micro and portable technology, we start to get an even better picture of how stressful and nerve-raking spring migration is for many ospreys.
Miniaturized solar-powered GPS trackers and newer solar-powered GSM (groupe spécial mobile) transmitters allow wildlife researchers to track movements of tagged ospreys in real time. Thanks to this new tracking technology we have a much better understanding of spring migrations.
A scientific project in 2013 by the National Parks of New York Harbor Conservancy used a solar-powered GPS device to show how fast an osprey is capable of flying during spring migration. An osprey named Coley travelled approximately 2,600 miles over 15 days from Ciénaga Pajaral, or Bird Marsh on the northern tip of the Republic of Colombia, situated near Panama, to reach the Jamaica Bay Wildlife Refuge in New York City. The bird traveled nearly nonstop at almost 173 miles per day.
In May 2012 at Jamaica Bay in New York City, wildlife researchers outfitted another osprey named, Coley II, with a GPS pack. The next year Coley II was late in arriving back to Jamaica Bay. The bird left Lake Valencia in Venezuela on March 16th but didn’t arrive to Jamaica Bay in New York City until April 5th. A trip that took 20 days. When Coley II did arrive, he had to contend with another male osprey that was trying to mate with his long-standing female companion. It was an “interloper” who had arrived earlier from the tropics and tried to pair off with Coley II’s established mate and nesting platform. Timing is everything, even for ospreys.
Although ospreys generally mate for life, a single bird will take on another partner when their established mate dies or doesn’t show up during spring migration. Each day that an osprey is not present at a nesting site decreases the strength of the bond with a mate, making a single osprey more likely to accept the advances of another osprey. Fortunately, Coley II arrived just in time to befriend his long-standing female partner and strengthen the pair bond once more. Another day or two and the outcome may have caused Coley II to locate a new mate and a new nest. Timing is everything, even for ospreys.
Stories of male ospreys arriving late to the nest are not uncommon. In 2015, the Squam Lakes Natural Science Center in New Hampshire tagged a male osprey Wausau, “named for the old Wausau Paper Mill that was an important part of the town of Groveton for so many years.” On March 23, 2016, Wausau flew about 150 miles north from his winter home in central Colombia and then surprisingly turned around and went back to his wintering area on the 23rd. No one is sure why, but Wausau took off again on March 28th and arrived at his nest in northern New Hampshire on April 18th. Due to this long delay, when Wausau arrived at his established nesting area, his mate from last year had already paired up with a new male. She probably thought poor Wausau had died. Fortunately, Wausau was able to successfully chase the intruder away, reclaim the nest, and begin the mating process with his long-established female partner.
Map by Ospreytrax at https://www.ospreytrax.com/html_files/Belle%202014.html
Perhaps the most famous and one of the longest tagged ospreys is Belle. This osprey was tagged on July 28, 2010 on Martha's Vineyard. The last signal was on April 26, 2017, after the radio failed. Belle completed 6 migrations from Massachusetts to the Amazon Basin in South America, with a total distance traveled of 82,961 miles (more than three times around the globe), and a total migration distance of more 50,000 miles. Along the way, Belle survived a major hurricane and several storms; and avoided numerous threats from humans and other animals, including a hungry alligator.
Belle flying over New York Harbor during spring migration to get to Massachusetts, but making a stopover to rest and feed along the Navesink River, NJ. Map by Ospreytrax at https://www.ospreytrax.com/html_files/Belle%202014.html
Why would an osprey be late or not show up at all to a nesting platform along the Jersey Shore? Stories of spring migration are even more interesting when you take into consideration the long winding path the birds often fly to reach a breeding site.
A study published by Mark S. Martell and others from a 2014 edition of the Journal of Raptor Research, shows that many of our east coast ospreys in the United States winter in South America with smaller amounts around Chesapeake Bay, Florida or on Caribbean islands, including Cuba. As spring approaches, ospreys who winter in South America make a long-distance journey past the Gulf of Venezuela to briefly rest in either Haiti, Jamaica, or Cuba, after a long overwater crossing of between 400 and 700 miles. It’s a tiring flight that typically takes 27 to 40 hours and involves risky nighttime travel. Once across the Caribbean Sea, nearly all ospreys will cross Cuba to the Florida Keys and then northward to breeding grounds. The birds travel as much as 5,000 miles from the Amazon basin, across the Caribbean Sea and up the Atlantic Coast before they end up at their breeding site. An incredible winged migration that normally takes two to three, sometimes four weeks, from start to finish.
Picture by Project OspreyTrack at Squam Lakes Natural Science Center in New Hampshire.
Migrating ospreys can cover thousands of miles during their spring travels, repeatedly traveling the same course year after year with little deviation. Moving across natural boundaries of rivers and tropical rainforests of the Amazon, the reefs and islands of the Caribbean Sea, the hills and valleys of Cuba, and past the largest subtropical wilderness in the United States known as Everglades National Park.
Along the way, ospreys have many stressful and worrying issues to deal with. One major hazard is weather, especially when crossing large bodies of water. The birds can be blown off course or get caught up in a severe thunderstorm or windstorm. This event will drain fat reserves (fuel) and put an osprey at risk of being too weak to continue. Ospreys cannot land on the water to rest like a gull. If an osprey gets tired over the open water, it will drown.
According to researcher Rob Bierregaard from Drexel University, one tired osprey attempted to rest and “ended up on a ship that took it to Portugal.” No one knows for sure exactly what happened to this poor, tired bird, but crossing large bodies of waters can be dangerous for birds of prey. “Most of the mortality is related to crossing the Caribbean Sea…. that’s when most adults disappear,” Bierregaard said.
Yet, many ospreys for whatever reason seem to welcome the challenge of flying over open water more so than any other bird-of-prey. Alan F. Poole, an expert on osprey ecology and behavior tells us in his classic book, Ospreys: A Natural and Unnatural History (1989), “Most diurnal birds of prey avoid over-water crossings of more than 9 miles because large bodies of water never generates the updrafts and thermals that make for efficient soaring flight. Instead, most hawks and eagles prefer to circumvent the intervening body of water, thus concentrating along shorelines, land bridges, or at narrow water crossings.” But not for Ospreys! They are the exception to the rule. During both spring and fall migrations, ospreys make perils water crossings over many miles of open water to begin another breeding season.
But weather and water are not the only problems. With nearly 9 billion people on this planet, ospreys have to deal with a few crazy people along the way, especially ones with guns and who will shoot birds. This happens when hungry ospreys try to take a fish from a private or commercial fish farm in the Dominican Republic, Haiti or Cuba. Many fish farmers do not take kindly to someone, even a bird, “stealing” a fish from their profit margins. According to a 2001 study by the U.S. Fish and Wildlife Service, about 14,000 ospreys are killed every year by fish farmers in several Latin American countries. Total mortality though could be higher, since at least 21 Latin American and Caribbean nations have fish farms along the birds’ migratory routes.
Shooting ospreys can take place anywhere including by people in the United States of America. In 2007, a Pennsylvania man pled guilty to killing an osprey with a .22 rifle at the Rainbow Paradise Trout Farm in Coudersport, PA, located approximately 110 miles east of the Allegheny River. The man, an employee at the trout farm, shot the osprey because the bird had been preying on fish.
Collisions with vehicles and powerlines are also are sources of mortalities for ospreys, particularly during spring migration when birds are in a rush and may not notice certain things to their demise. Another threat are oil spills in the waters of Venezuela. A September 24, 2020 article in The Washington Post written by By Mariana Zúñiga and Anthony Faiola tell us: “Venezuela’s once powerful oil industry is literally falling apart, with years of mismanagement, corruption, falling prices and a U.S. embargo imposed last year bringing aging infrastructure to the brink of collapse. As the government scrambles to repair and restart its fuel-processing capacity, analysts are warning that ruptured pipelines, rusting tankers and rickety refineries are contributing to a mounting ecological disaster in this failing socialist state.” Many ospreys die every year from polluted water near Morrocoy National Park and in the Gulf of Paria.
But if not oil, then DDT. During the 1950s and throughout the 1970s in the United States, DDT (Dichlorodiphenyltrichloroethane), or more correctly its breakdown creation DDE, a colorless, tasteless, and almost odorless chemical compound used as an agricultural and household pesticide, caused the collapse of osprey populations throughout North America. The pesticide seeped into local waterways through runoff and accumulated in the tissues of marine organisms, including fish.
This bioaccumulation, the gradual accumulation of substances in an organism, of DDT seriously affected top predators, including ospreys, bald eagles and peregrines. The toxin impaired a bird’s ability to reproduce. DDT caused eggshell thinning which led to fewer and fewer young to replenish the population. Toxic chemicals probably also killed off some adults as well.
Alan F. Poole tells us in his book, Ospreys, The Revival Of A Global Raptor, that most population declined very quickly…many by at least 50% and a few by almost 90%.” Poole goes on to declare that DDT, “interfered with the physiology of eggshell formation in females. Consequently, eggs were laid with thin shells and often failed to hatch; year after year populations struggled to gain new recruits.”
The good news is that osprey populations have shown a gradual increase since DDT and similar toxic substances were federally banned in the United States in the 1970s. Water quality has also been slowly improving in the United States since the establishment of the Clean Water Act of 1972. Various government and nonprofit organizations and volunteers have also been busy building osprey nesting platforms to provide suitable nesting areas for the birds, as their coastal habitat largely became developed and fragmented during the DDT era.
According to the 2019 New Jersey Osprey Project Report, there were 669 occupied osprey nests — the most ever recorded in New Jersey – with around 95% of the population utilizing manufactured wooden nesting platforms. Of course, not all the nests were productive. Out of 669 nests, 488 were active and produced 932 young. Great news compared to having only about 50 nests in 1974 statewide. Osprey populations are on the rebound.
An osprey nest that is tangled up in fishing line.
Yet as ospreys return to a nesting platforms in the spring, the birds are unfortunately welcomed by one more sinister and deadly threat. This time it’s plastic waste.
Adults and young are particularly at risk of becoming entangled in plastic string, bags, containers, or monofilament fishing line. The 2019 New Jersey Osprey Project Report also tells us that volunteers have started to remove trash and collect data from osprey nests. In 2019, out of 189 nests they monitored, 42% contained plastic debris. We live in a society where unfortunately plastic litter is very easy to find, and since the birds live close to humans, plastic trash are often found in their nests.
Plastic debris can be seen in this nesting platform and many others along the Jersey Shore.
Why Do Ospreys Migrate?
Why do it? If given a choice, I’m sure many ospreys would prefer to stay year-round in the same location to avoid a lengthy and stressful migration twice a year. But Alan F. Poole states in Ospreys: A Natural and Unnatural History, that ospreys need a good supply of fish to survive, which is not possible to find during the winter in North America. Poole writes that fish, “are cold-blooded and thus sensitive to changes in water temperature. When temperatures drop, most avoid the colder shallows and surface waters where Ospreys can reach them. Thus even where northern lakes and bays do no freeze in winter, Ospreys attempting to winter over would probably starve.”
Why do we care about ospreys?
These fish hawks play an important role in the health of an aquatic ecosystem. Ospreys help to provide balance among fish populations and keep fish populations genetically healthy by eating sick or scrawny individuals. Ospreys are also a valuable indicator species for monitoring the long-term health of an aquatic ecosystem. Birds of prey are extremely sensitive to many environmental changes in an ecosystem. Since an osprey’s diet consists almost entirely of live fish, an abundance of nesting ospreys with many hungry young suggests water quality and fish populations might be improving to support many hungry beaks and gizzards.
What you can do to help protect ospreys:
Avoid getting too close to nesting sites during the breeding season. Always maintain a respectful distance from wild animals. Always carry binoculars to view wildlife from afar. If an animal vocalizes when you're near, you are too close! Immediately back off.
Restore coastal and wetland habitat.
Preserve existing coastal habitat, including wetlands and dunes.
Help keep local waters clean, healthy, and safe.
Recycle used fishing Line.
Volunteer to help members of Save Coastal Wildlife install new nesting platforms at wetland sites along the Jersey Shore. Artificial nesting platforms are generally more stable and safer than the natural nesting areas (usually dead trees). Nesting success is also commonly twice as high on artificial sites compared to natural sites.
If you don’t live near an osprey nest, you can always watch the action online. There are many osprey nests on the web to watch. In 2019, The Conserve Wildlife Foundation of New Jersey installed a new osprey cam in Barnegat Light. The action can be seen here http://www.conservewildlifenj.org/education/ospreycam/
