The Osprey's Fight for Survival
Unfortunately, the Osprey can't talk. If they could, these hawk-like birds might explain why they're frustrated in their attempts to raise chicks in New Hampshire. None of the estimated seven to 11 pairs of Osprey nesting in the Granite State in 1981 was successful in reproducing young, a situation which probably worries the birds and certainly worries the staff of the Audubon Society of New Hampshire (ASNH). For the past two years, ASNH biologists have been studying the Osprey in an effort to understand what is happening to the bird, and why it appears to have such difficulty bringing up a family. At this point, there are more questions than answers.
Thus far, only two things are clear: more research needs to be done, and a new source of funding needs to be found. Endangered Species Grants from the US Fish and Wildlife Service have, in part, supported the ASNH studies of Bald Eagles, March Hawks, Cooper's Hawks, Common Terns, Red-shouldered Hawks, and the Osprey since the beginning of 1980. By the end of this month, however, when these funds dry up, future work with each of these species will depend on the Audubon Society's ability to find financial support elsewhere. Despite the pressing financial headaches of the effort, the ASNH's Endangered Species Program Project Leader Carol F. Smith insisted that work would continue.
"The study of the Osprey and the Terns on the coast are our highest priorities," she said. "We'll find a way to keep working with these birds even if that's all we're able to do."
The immediate reason for concern with the Osprey's plight is the result of field work the Audubon Society undertook two summers ago. While this preliminary survey located a minimum of a dozen adult birds nesting in the state, it found that only two chicks were produced, a number far below the birth rate needed to maintain an Osprey population. Because of this, the Audubon Society hired wildlife biologist Chris Ricardi and gave him specific instructions to tabulate the exact number of Osprey young and to try to determine why more birds aren't being born. Though he has yet to complete his final report, Ricardi's preliminary findings indicate that something isn't right.
Ricardi spent the summer based in Errol, a village 37 miles north of Gorham on the shore of Umbagog Lake - a region where all known Ospreys in the state nest. As Ricardi explained, the birds aren't foolish; they know a good environment when they see one. "There are several reasons why the Osprey come to Umbagog," he noted. "One reason is that the lake is shallow, and the shallows extend well out from the shore into the lake. The Ospreys have better luck fishing in water ranging from 2 to 3 inches to a foot deep." Unlike other fish-eating birds, such as the loon and the pelican which go head-first after their food, the Osprey swoop down and snatch fish from the water with their razor-sharp talons.
By contrast, the deeper waters of the Connecticut Lakes, where the bottom reaches a depth of 30 to 40 feet just off shoreline, is ideal for trout and salmon but futile for Osprey. While the bird had been spotted in this area, Ricardi pointed out that the abundant supply of yellow perch, whitefish, and hornpout in Umbagog made it a more suitable home. In addition, the nearby shallows on the Androscoggin and Magalloway Rivers provided good fishing.
A second reason why the Osprey have chosen Umbagog as their nesting grounds is because of the area's surrounding wetlands. Close to the lake where the water has flooded sections of the forest, dead white pine and spruce trees offer excellent and ample nesting sites. with twigs and sticks, Osprey construct their nests 40 to 90 feet about the ground, giving them unobstructed vision of the area and good protections against foraging raccoons, which prey on their eggs. Each of the dozen nests Ricardi identified was within a mile or two of Umbagog.
Understanding why Pandion haliaetus fares so poorly in New Hampshire is a complex process made more complex by the bird's life cycle. During each stage as it grows from egg to chick to adult to parent, it is vulnerable to a series of natural as well as man-made dangers, and research is just starting to uncover how these dangers affect the bird.
From ice-out at the beginning of April through early May, the Osprey return to Umbagog from their winter layover in the southern climates. No one is certain exactly where the birds return from since their range extends from the southern United Stated through South America. Once here, however, the adults set to work repairing their former nests or - if need be - building new ones. The unattached males then do their best to attract and impress the single females, flying and darting about the female as she watched from her nearby nest. When the urge hits them, some females will join the courting male in his flight.
After pairing up - in a bond that endures for life - the birds mate, and several days later the female lays from two to four eggs. Following 28 days of incubation, the chicks hatch out and immediately demand food. "For the first two weeks," Ricardi explained, "the adults will capture fish, eat them, and then regurgitate what they've eaten to the young. Later, they'll tear up the fish and feed the chicks small pieces." Having healthy appetites, the chicks mature rapidly, and by the fourth or fifth week their flight feathers appear. From this point until they leave the nest at eight weeks, the chicks often perch on the rim of the nest and dance about, exercising their wings in preparation for flight.
At eight weeks of age and nearly as big as their parents, the chicks begin to fend for themselves. Though similar in size, the mottled brown and white back of the immature birds stands in striking contrast to the solid dark back of the adult. Following a summer's feeding, the birds begin to migrate southward, leaving one at a time or in pairs, taking a relaxed tourist-like approach to their trip. "They might fly for a day then stop if they find a good fishing spot," Ricardi pointed out. "They set a leisurely pace."
Since Ospreys take their time coming to and leaving the state, their sighting by bird watchers in different regions has created some confusion. "We've had reports that Osprey have been seen all across the state," Smith recalled, "but it's usually a migrating bird. If someone spots a bird in July, though, there may be something going on."
In their first year, the young Osprey remain in the southern climes the year-round, and only return north the following spring. As sophomores they tend to be nomadic. "We suspect that they wander around looking for suitable nesting sites," Smith added. "They may also account for reported Osprey sightings from the southern parts of the state." In any case, the entire cycle begins again when the Osprey turns three, and it may continue for a dozen years or more. Typically, the bird lives from 12 to 14 years or more. Typically, though 16 and 17 are not uncommon.
While Smith and Ricardi cautioned that data collected from the two-year study of Ospreys was neither complete nor conclusive, these first findings aren't encouraging; the population was small and unproductive. "We found 12 nests," Smith said, "but some of them were old and some of them weren't used. We also had one pair of Osprey who left their nest after failing to hatch their eggs and moved to a second nest and tried again." In addition, Ricardi pointed out that a few of the nests weren't found until late August, after the time when most Osprey would have hatched their young. These factors made it difficult to arrive at an exact head count.
"But based on what we know," Smith continued, "there are a minimum of 15 and a maximum of 23 Osprey nesting in New Hampshire - somewhere between seven and 11 pairs, plus one odd one, which might be an immature bird." These seven to 11 pairs will want to forget the 1981 season. "Of those nesting this summer, we believe that three laid eggs and two hatched chicks," she added, " but we're not aware of any young having hatched successfully."
"I found one pair which left its nest before the eggs hatched," Ricardi said. "In a second nest where the chicks did hatch, they were alive after five weeks, but they had vanished by the seventh week," Though there is a slight chance that these chicks did live, I don''t think they did," he added. "I never observed then in exercise behavior, flapping their wings in the nest, and they usually need eight weeks before they're able to fly with their parents."
Natural factors may account for some nest failures, though they can hardly explain everything. Predators like the raccoon may have stolen Osprey eggs, and Great Horned Owls may have attacked unguarded chicks. Built on dead trees, the nests of the Osprey are sometimes victims of high winds which can quickly flatten a summer's labor. Forest Service biologist Jim McGowan recalled that one such nest near Round Pond in the Evans Notch District of the White Mountain National Forest met this end several years ago. More plausible answers point to the changes that man has made in the environment.
Among the most potentially serous of these is the lingering effect of DDT, a pesticide widely used in this country following the Second World War. According to Roger Torey Peterson, the effects of DDT could prove devastating to Osprey. Thirteen years ago he wrote: "Fish. . . also store DDT and other hydrocarbon poisons in their tissue and because of this it is possible that the Bald Eagle and the Osprey, both fish eaters, may disappear from the Atlantic Coast within the next decade or two. The birds now sit for weeks on unhatched eggs and few young are raised - on analysis, both Osprey and Eagle eggs have shown significant amounts of the life-destroying chemicals."
Used widely from the Chesapeake Bay to Connecticut as a weapon against mosquitoes, DDT did wipe out the Peregrine Falcon east of the Mississippi, Ricardi explained. Even though it has since been banned, its residual effects couples with other chlorinated hydrocarbons (used in pest control) spell trouble for the birds. Aside from causing Osprey to lay sterile eggs, Ricardi noted that it has other harmful side effects as well. "With an overexposure to hydrocarbons, the bird's sex hormones are inhibited," he said. "If there's too much of a concentration in the body tissue, they're prevented from reproducing without ever having been kicked into gear."
Tracing the source of this unwanted birth-control, however, illustrates a problem common to ornithology: keeping track of the birds. "In winter they range as far south as South America and the Gulf of Mexico," Ricardi explained. "We don't know if they winter together or in different areas, nor what they're exposed to in the places where they go. We have a lot more to learn before we know what's happening to the population."
In addition to carrying unwanted chemicals, the Osprey at Umbagog may be overtaxing the resource. "We believe that there may be a problem at the lake because there might not be a large enough fish population to sustain the birds," Ricardi said. "They may be expending so much energy in trying to catch fish to feed their young that they're not able to do a good job." To determine if this is one of the problems, Ricardi plans to carefully follow the fishing habits of one pair next summer when the male is supplying his young family, By comparing known data on the ratio of successful catches per dive, he'll be able to see if overfishing is a problem. For now, it's only one possible explanation, "This year," he concluded, "has been a very poor one for Osprey."
Other factors, unrelated to man's activity, further hamper the effort to evaluate New Hampshire's Osprey population. "Raptors (a class of birds including Hawks, Eagles, Falcons and Osprey) take a year off from their egg laying chores every now and then," Ricardi explained. "They haven't evolved for great reproduction, but for a slow and steady propagation. Even without the man-made problems, it's hard to know how they'd reproduce naturally."
Whether or not the limited data collected from the last two summer's work is typical for Osprey in the State, it does concern the Audubon Society staff. A study by biologists Henny and Wight showed that raptors need to reproduce between .95 and 1.3 offspring each year to maintain their population levels. Clearly, the crew in the Granite State has fallen far short of this necessary pace. Just as clearly, the responsibility lies less with the birds than with the actions of humans, unintended and otherwise.
"In the past you were considered a good hunter if you cold shoot down a hawk or other raptor," Ricardi said. "People just didn't realize that these birds aren't as prolific as pigeons. "Sadly enough, a few careless people still don't realize this; last year, four Osprey were shot in New Hampshire during their fall migration."
Assuming that it is able to continue to carry out its work with the Osprey, next summer's research may shed further light on the bird's status as a breeding species in New Hampshire. "The effects of DDT are beginning to wane," Smith said," and populations are beginning to come back, but there's so much we don't know about the bird. We don't know if they're hatching, or if older or younger birds are reproducing. We don't know if they winter in the same of different areas or what contamination they may be picking up. There are so many problems that we don't even know what all the problems are."
From the time it was first named - from Latin Ossifraga meaning "bone-breaker" - to recent years when it was hunted as a game bird and prized for its feathers, the Osprey has been badly misunderstood. But as Thomas Nuttall wrote, the bird deserves better:
". . . the harmless industry of the Osprey, the familiarity with which he rears his young around the farm, his unexpected neutrality toward all domestic animals near him, his sublimely picturesque flight and remarkable employment, with the strong affection displayed toward his constant mate and long helpless young . . . are circumstances sufficiently calculated to insure the public favor and tolerance towards this welcome visitor."