ISLE ROYALE – Rangers at Isle Royale National Park recently announced the births of peregrine falcon chicks and wolf pups at the isolated island ecosystem.
In a recent news release, rangers said island animal populations are generally small with fewer species than on the surrounding mainland and that Isle Royale’s biodiversity is generally lower because the islands’ isolation has restricted migration of organisms from outside populations.
Consequently, animal births on Isle Royale are often celebrated. The park is home to only 19 species of mammals, far fewer than what exists within mainland environments.
In 2012, peregrine falcons, a state listed endangered species, nested and successfully fledged young on the island for the first time in 57 years. That success was repeated this year with two chicks reared to fledging on Passage Island.
“Last year was quite a shock to find a breeding pair of falcons,” said Isle Royale Chief of Natural Resources Paul Brown. “This year, we hoped the pair would return and we were very happy to see nesting activity.”
Brown said there there initially three chicks in the nest, but over the course of the next few weeks one chick disappeared. The two remaining chicks were successfully reared. With the addition of these two new birds, the island population of peregrine falcons is currently thought to be between five and seven individuals.
Historically, peregrine falcons were first documented at Isle Royale in 1890 with a nest at the Gull Islands northeast of Passage Island. Rangers said that after World War II, increases in the use of pesticides such as DDT and PCBs in plastics contributed to declining raptor populations.
“These chemicals concentrate as they work up the food chain, becoming biologically problematic in top predators by reducing calcium in the eggshells, which thins the shell and increases chances of breakage,” rangers said in a news release.
Prior to 2012, the last known recorded nest on Isle Royale was from 1955, when park ranger Bob Janke reported one at the Palisades near Blake’s Point on the east end of Isle Royale. By 1964 there were no occupied nesting cliffs in eastern North America.
Rangers said that in the 1980s, natural resources specialist Bob Krumenaker began a program to reintroduce peregrine chicks, rearing them to fledging age in hacking boxes on cliffs on the Feldtmann Ridge on the west end of the island, at the Palisades, and on Passage Island. During hacking, food, shelter, and protection from predators are provided until the chicks begin to hunt for themselves.
In 1987 five fledglings were released at Feldtmann Ridge, with five more released in 1988. Then 10 more were released in 1989 from the Palisades; 18 in 1990 from Palisades and Feldtmann Ridge, and 12 more in 1991 from Feldtmann Ridge. All but two of these fledglings were known to survive until they dispersed from the site and one was retrieved at Hawk Ridge in Duluth in fall of 1991.
Wolf pups, at least two of them, were also born at the park this year.
Rangers said that for the past several years the wolf population has been slowly declining, to a historic low of eight animals at the end of winter study in March. The newborn wolves brought the total population up to at least 10 animals.
“It is always exciting when we learn about successful reproduction of wildlife in the park, and the birth of two wolf pups is especially good news,” said Isle Royale Superintendent Phyllis Green. “The wolves continue to surprise us with their resiliency. While we were very happy to learn about the birth of the pups, we are still concerned about the population and are in the process of evaluating options on how to deal with the population in the future.”
John Pepin can be reached at 906-228-2500, ext. 206.