Keeping track of an island osprey
A young member of our community is about to make a trip of a lifetime. In a few weeks, he will leave the safety and security of the island and travel 3,000 miles south through North Carolina, Georgia, Florida, Cuba, the Caribbean, and the Dominican Republic before resting in South America.
The trip will take about 30 to 35 days, and he will have a 50 percent chance of surviving.
The reward? A two-year vacation near Venezuela, where most of his time will be spent improving his fishing skills. This young traveler’s name is Conanicus, and while we will not see him again until the spring of 2007, he will be sending us updates about his journey every day. Conanicus is one of the two young ospreys that hatched this spring in Great Creek, and he was recently outfitted with a tiny radio tracking device that will send scientists information on his location via satellite.
Rob Bierregaard, a biology professor from the University of North Carolina at Charlotte, spe-cializes in tracking birds of prey, or raptors, such as owls, hawks, and ospreys. Bierregaard came to Jamestown to help add a new dimension to the Conanicut Island Raptor Project.
The Conanicut Island Raptor Project, co-chaired by Chris Powell and Besty Gooding, began with the idea of mounting a video camera on the osprey nest in Great Creek. The objec-tive of the project was to create an educational experience for Jamestown school children. Now, the video camera is linked to the project’s Web site, www.conan-icutraptors. com, and children can watch the osprey nest from the time the adult female lays her eggs in the spring to the time the young osprey begin their migra-tion south in the early fall.
Bierregaard has added an exciting aspect to the project. By fitting Conanicus with a radio transmitter, children will be able to map the osprey’s migration route daily, learning more not only about ospreys, but also geography, math, and physics.
Bierregaard began tracking ospreys by satellite in 2000, when he collaborated with Mark Martell, a biologist at the University of Minnesota. Before satellite technology became prac-tical for this type of application, biologists tracked migrating ospreys by attaching a numbered band around each ospreys’ leg. When someone found a banded osprey, he or she would call the 800 number listed on the band and report the bird’s location. Using this tracking method, biol-ogists knew where ospreys migrated to, but still did not know anything about how they got there and what happened along the way.
As satellite technology advanced, scientists were able to develop radio transmitters that were small and light enough to be attached to a bird. The trans-mitters used by Bierregaard weigh 1 ounce and are fitted to the osprey’s back like a tiny backpack, with straps across the bird’s chest. The transmitter has little solar panels in order to recharge and sends out signals that are picked up by satellites and sent to a computer in Maryland.
Now, Bierregaard knows the location of the tagged ospreys daily, a big step in learning about their migratory patterns. Each transmitter costs $3,000, and the transmitter that Conanicus is wearing was previously used to track an osprey from Martha’s Vineyard.
Ospreys are large fish-eating raptors with a wingspan of up to 5 feet. Ospreys’ vision is many times more acute and at a higher resolution than humans’, allow-ing the raptors to spot fish below the surface. Remember, when you look at an object in the water it is not actually where it appears to be. Ospreys’ eyes can compen-sate for this refraction. Ospreys catch their prey by diving feet-first in a plunge dive from per-haps one hundred feet above the water, and snatch slippery fish in their long, sharp talons. Then the osprey will orient the fish head-first — torpedo fashion — to reduce wind drag as he flies. Ospreys must live in big, clear areas near water, and although the nests are often built on the top of utility poles, they do not need to be that high. The only requirement is that the nest be the highest thing around. In the Westport River, for example, the ospreys perch their nests 5 or 6 feet above the water, and they often build nests on the tops of channel markers.
The ospreys’ migration pat-terns, however, are unique among raptors. According to Bierregaard, ospreys are “hard-wired” with two instructions when the days get shorter and the weather gets colder: fly south, and stay over land. Ospreys from the East Coast always fly south to Florida, on to Cuba, and eventually stop in South America. West Coast ospreys only fly as far as Mexico, and mid-West birds go to Mississippi or the Yucatan, or fly east first and then take the Florida-Cuba route. Ospreys are observed in Florida year-round, however, and until recently, biologists have wondered whether Floridian ospreys migrate. Through satel-lite tracking, Bierregaard and his colleagues have discovered that while Florida ospreys do leave and go further south in the win-ter, ospreys from Maine and Nova Scotia often end their jour-ney in Florida, which explains why ospreys are present all year.
Male and female ospreys take separate winter vacations, which, Bierregaard jokingly pointed out, is “why they can stay mated for life.” Right about now, the young ospreys in the nest at Great Creek should begin to experiment. They will have to learn to fly and fish on their own, although they will have a trial-and-error period dur-ing which the adults will give them an “allowance” of fish, so that the young birds do not go too hungry.
The young ospreys learn quickly, and for good reason — as hormones leave the adults’ bodies, they become less and less interested in parenting. In a few weeks, the female, exhausted from a long spring and summer of taking care of her babies, will leave and fly to her wintering spot in South America. Then, in mid-September the male and the young osprey will leave for South America separately.
In the spring of 2006, the adults will come back to the same nest in Great Creek and start a new family. The young osprey, however, will stay in South America for two years, after which they will be old enough to breed. The young male osprey will then return to the area where they were born, usually within 10 to 20 miles. The females, however, will move further away. According Bierregaard, this is nature’s way of reducing inbreeding.
Bierregaard illustrated how satellite tracking has made a sig-nificant difference in understand-ing osprey behavior and how the raptors are threatened. Bierregaard explained, for exam-ple, that all East Coast ospreys fly through Cuba, creating a bot-tleneck of birds over the narrow strip of land. This makes the osprey population especially vul-nerable if, for example, Cuban fish farmers decide that they do not like the ospreys preying on their fish.
Bierregaard also learned about a whole new part of the ospreys’ biology by tracking ospreys on Martha’s Vineyard. When fishing in the salt water on Martha’s Vineyard was difficult, Bierregaard observed the ospreys leaving their nests on the Vineyard and flying to Connecticut. The ospreys would hang out in Connecticut for three or four days, fish in the fresh water ponds, and then commute back to Martha’s Vineyard. Bierregaard deduced that since competition for nests is so fierce, the ospreys did not want to aban-don their salt water nests on the Vineyard, so they traveled back every few days to keep an eye on their property.
Ospreys are now protected under federal law, after U.S. pop-ulations were decimated in the 1950s and ‘60s by the wide-spread use of DDT and other pesticides that contaminated aquatic food chains. Prior to the introduction of DDT, Bierregaard said, there were more than 1,200 pairs of breeding osprey between New York and Boston. But by 1970, the peak of the DDT era, there were only 170 pairs. At that time, Paul Spitzer, the “godfather of modern osprey work,” began researching what was going wrong. Spitzer eventually deter-mined that DDT was causing the ospreys to lay eggs with thin shells. When the mother sat on her eggs, they would crack.
He also determined that there was a problem with the gas exchange within the egg. The environment within an eggshell is in a delicate balance, the right amount of carbon dioxide and water must be released and the right amount of oxygen let in.
A lawsuit filed by several young Yale lawyers successfully banned the use of DDT and many raptor species, including the osprey, bald eagles, peregrine falcons, and hawks, have made tremendous comebacks.
According to Bierregaard, there are now close to 1,000 breeding osprey pairs in New England, and between 18,000 and 19,000 pairs in the lower 48 states. “Rhode Island is fortunate that it is small enough that we can count all the pairs. Rhode Island is the best monitored state in the nation,” Bierregaard said.
Humans still create significant challenges for osprey recovery, however. Raccoons, for example, are one of the ospreys’ natural predators. The raccoon popula-tion, however, has exploded as they feed on our garbage. Chris Powell is planning on installing a predator guard on the osprey pole in Great Creek to protect the osprey from the raccoons.
Conanicus will be the first osprey in Rhode Island to be fit-ted with a satellite transmitter and elementary school children will soon be able to track his journey online. Bierregaard is also tracking an osprey from Martha’s Vineyard and suggested that students could “race” the two ospreys to South America.
Anyone who is eager to learn more about osprey, the Conanicut Island Raptor Project, or Bierregaard’s work can go to www.conanicutraptors.com for more information.