Falcon Reintroduction Program Success Takes Wing
November 24th, 2020
Falcon Reintroduction Program Success Takes Wing
November 24th, 2020
Climbing a cliff overlooking Valley Covein May of 2018, a team of Acadia National Park biologists moved quickly to band four endangered peregrine falcon chicks. With the help of rock climbers, they removed the chicks from the scrape — the nest of scratched-out gravel — and brought them to a work area away from the ledge. As one gloved biologist expertly held each fluffy white ball with oversized yellow feet, the other quickly attached two metal bands to its legs. What was special about the second “color band,” as they referred to it, was a prominent code that could be read from a distance.
Two years later, a dedicated birder andphotographer, Trish Berube, was monitoring two adult peregrine falcons near the Franco-American Heritage Center at St. Mary’s in Lewiston, Maine when she did exactly that. The birds were doing the “fast switch-offs” typical of a pair sharing incubation duties. When Berube focused her spotting scope on the female, the larger of the two, she coulddiscern a code and reported it to the Maine Department of Inland Fisheries and Wildlife (IFW). Dr. Erynn Call broke the news that the female was one of the clutch banded by the team in Acadia in 2018.
According to Call, the Gothic church spire in Lewiston has been the setting for repeated breeding attempts by peregrine falcons dating back to 2003. The only success prior to this year occurred in 2009. Two chicks, a male and female, fledged. In September, Berube watched the Acadia progeny han ing around Lewiston, now exuberant juveniles chasing each other and observing traffic at a local intersection.
This story of scientific management and communication between experts and volunteers is just one in a series of successes in the reintroduction program that began three and a half decades ago across the U.S. Peregrine falcons, once on the brink of extinction due to widespread use of the pesticide DDT, have made a stunning recovery.
In fact, the national population is now so strong that peregrines were removed from the Federal Endangered Species list in 1999. The recovery in Maine has been “promising,” but the species remains on the state’s Endangered Species List, according to Call. A survey conducted last year documented 38 pairs with 23 breeding pairs.
Several of those peregrines nested in Acadia—at the Precipice, Jordan Cliffs, and Valley Cove. In all, they produced nine juveniles in 2019. This year that number dropped to five, according to Bik Wheeler, a National Park Service wildlife biologist who was among those on the banding mission to Valley Cove two years ago. That is partially because the Precipice pair (and they do mate for life) was unsuccessful, despite two attempts.
Breeding falcons begin their courtship in February or March with elaborate “flight play” in which both males and females participate. As they establish their nests, their behavior becomes more territorial. The female lays three or four eggs in March or April. Incubation, which takes 30 to 36 days, is carried out by both parents (though the female does most of the work).
Even when the chicks do hatch, success is not guaranteed. A cold rain or late snowfall can threaten their survival if they have not yet accumulated enough body mass and all those fluffy feathers. Inadequate food and predation by great horned owls also imperil the chicks.
For pairs breeding in urban settings, risks begin even earlier. On a bridge, skyscraper ledge, or copper church spire (as was the case in Lewiston), the female lays eggs directly on metal or concrete and these surfaces pose risks when they become too hot, too cold, or too wet.
Chicks fledge in late June or July, but are not independent for two or more months. They must learn to hunt and handle prey in flight. Eventually, their skill becomes so great that pairs can exchange food while they are flying.
In more urban settings, certain parts of the artificial environment and transportation infrastructure can present hazards for peregrines. They may strike buildings and windows, automobiles and trains, power lines and cables. According to one study, collisions with aircraft cause the highest mortality.
So, that raises the question: why leave Acadia? After all, the national park offers what peregrines like: high, inaccessible ledges for nesting; large open areas for hunting; habitats near water that are plentiful in birds; and little disturbance by people when trails are closed during nesting season.
In part, the answer to the question is that wild peregrine falcons wander, as the Medieval Latin origin of their name, “pilgrim falcons,” suggests.
Although these raptors have a strong preference for nest types similar to where they fledged, some do travel quite widely. (Scientists talk about their “dispersal.”) Females have been known to go twice as far as males. To find mates and avoid inbreeding, they can travel these longer distances because they are larger. In addition to mating, peregrines also disperse in search of food.
A study published in 2013 provides more insight into the odysseys of New England peregrine falcons. Almost 1,000 chicks born in six states between 1990 and 2009 were banded as nestlings. Because one-quarter of them were encountered again, scientists learned a lot about their movement patterns.
For example, one quarter of the peregrines that were sighted had traveled outside of New England, not only to other eastern statesbut also to three Canadian provinces, Cuba, and Nicaragua.
Although the tendency to settle at places similar to where they were raised was confirmed once again, scientists documented movement from rural cliffs to urban structures and vice versa.
These scientists also found that where peregrines are born— natural cliffs versus urban structures—did not affect survival rates. Another study, conducted a decade earlier in California, had observed not only higher survival but also higher fecundity rates among peregrines fledged in urban areas. (That may have something to do with the more plentiful food sources cities provide such as pigeons.)
So, the news of Acadia’s native daughter successfully fledging chicks in Lewiston is actually another feather in the cap of thenational park’s reintroduction program. Said Wheeler, “If the chicks coming from Acadia are dispersing across the region and being very successful themselves in raising young, then we are meeting a larger goal and impacting the overall population.”
“It is the ultimate win,” added Acadia ornithology ranger Patrick Kark.
LYNN FANTOM is a former NYC marketing executive. Fantom writes about the outdoors and aquaculture, especially in Maine, where she now spends half her time.
This article appeared in the Fall 2020 Acadia magazine.