Department of Natural Resources non-game bird biologist Allisyn Gillet, Indiana State University graduate student Katie Spicer and ISU biology professor Steven Lima all hold young peregrine falcons in the Sycamore Building in Terre Haute, Indiana.

Overhead, high-pitched cackles echoed through the sky as a pair of peregrine falcons circled closely above a 12-story building in downtown Terre Haute, Indiana.

The adult mates were displaying concern as biologists wearing helmets removed three chicks from a nest box atop the structure. Biologists also removed one unhatched egg.

This is the first year chicks have been hatched on the Sycamore Building, after the nest site was relocated there from a pair of buildings on the nearby Indiana State University campus that were being torn down.

John Castrale, a non-game bird biologist who is retired from the Indiana Department of Natural Resources, and DNR non-game biologist Allisyn Gillet soon returned the four-week-old chicks to the nest after placing two light aluminum bands, one on each leg, on the young birds.

Bands are put on the birds to learn about their longevity, survival rates and dispersal rates, Castrale said. A blood sample was also taken from one bird for genetic tests.

“These birds actually [had] disappeared as a nesting bird from the entire eastern United States by the 1960s,” Castrale said. Efforts from falconers, federal and state governments, private individuals and organizations “brought this species back” from being a federally endangered species, he added.

The tagging is part of the Midwest Peregrine Society population recovery program, based in Minneapolis at the University of Minnesota. “It is probably the best studied of any large scale restoration effort,” Castrale said.

The falcon’s demise was because of widespread use of pesticides in the 1950s and 1960s, particularly the use of DDT, which caused the falcon’s eggshells to thin, resulting in egg breakage and reproductive failure. DDT was banned in the United States in 1973.

“There are probably about 20 pairs [of the falcons] in Indiana, in 20 territories,” Castrale told the Terre Haute, Indiana Tribune Star. “There are about 14 pairs that nested and have eggs this year. There are a couple of sites that we have not been able to get access to that may also have birds.”

Peregrine falcons live mainly on mountains, in river valleys and along coastlines, but are increasingly migrating to cities. The Midwest is home to about 300 pairs of falcons, Castrale said, with the largest population concentrated along the Great Lakes, the cliffs and river bluffs.

“This is a species that has adapted to urban industrial settings,” Castrale said. “In Indiana, all of our nests are either on a building, a smoke stack or under a bridge. They don’t build a nest, they use just a ledge. If there is some debris or gravel, that’s what they like.”

The standard leg band for the peregrine is a silver metal band issued by the federal Bird Banding Lab. The band is inscribed with a website and unique 9-digit code that allows birds to be identified.

A blue band, from the DNR, can be read from a distance with binoculars or a spotting scope. About 75 to 80 percent of peregrines in the Midwest have been banded, Castrale said.

The blood sample from the chick, Castrale said, will allow biologists to study genetics to determine how diverse the falcon population is and “look at inbreeding. Occasionally, we can identify that we have had a mother that mates with sons or grandsons or whatever. We know that females on average will settle about 100 miles from where they were raised. Males about 200 miles or anywhere up to 1,000 miles in the Midwest,” he said.

The falcons are bird-eating raptors and will eat pigeons, blue jays and morning doves. “They will chase away crows from their nest, but not eat them, as crows are about as big as a peregrine,” Castrale said. “They will take anything from a small duck or even a seagull. They are strictly aerial predators.”

Falcons have been documented to live as long as 19 years. However, after 14 years of age, females are too old to lay fertile eggs. Females are larger than males, Castrale said, and are roughly 20 percent longer, and at least a third heavier than the male.

“The average age of a breeder is about 8. They potentially could nest when they are a year old, but for the most part they don’t until they are about 3 years old, mainly because most of the nest sites are occupied now,” Castrale said.

The falcons generally lay two to five eggs, with four eggs the most common. “Hatchability is about 80 percent, so it is not unusual for one or two eggs not to hatch,” Castrale said.

About 50 percent of the birds will not survive for a year. After that, annual survival rate is about 80 percent, Castrale said.

Greninger writes for the Terre Haute, Indiana Tribune Star.