State wildlife experts on May 30 banded the two peregrine falcon chicks from this spring’s nesting atop the W.E.B. Du Bois Library.
The male and female, hatched May 10, are the survivors from a brood of four laid around April 11.
As their calling parents whirled and dived overhead, Tom French, assistant director of natural and endangered species for the state Department of Fish and Game, removed the two chicks from their nesting box and baned them, assisted by endangered species biologist David Paulson.
The bands, which are coded by color and carry letters and numerals, allow wildlife researchers to track the movements and histories of the birds over time.
French said there are an estimated 40 nesting pairs of peregrines in the state, with about 20 producing chicks this spring.
Known nesting sites include tall building, bridges and quarries, as well as natural cliffs. The birds are comfortable with man-made nests, as well as their own. Formerly listed as endangered, the species is currently listed as threatened.
Historically and before DDT pesticide was in common use, the most successful season for peregrine falcons in Massachusetts was 1948, when 14 nesting pairs were counted. But conditions declined with the use of DDT, and the last peregrine chick was fledged in Massachusetts in 1955. By 1966, not a single nesting pair could be found in any state east of the Mississippi River. DDT was banned in 1972.
Peregrine falcons have been nesting on campus since 1998 and continuously at the library since 2003. One pair nested at the library from 2003-14 and hatched 37 chicks.
This year’s falcon parents are new to the library and because they are not banded, their origin is unknown.
French said banding is best done when the chicks are between 3 weeks, when their legs reach full thickness, and 5 weeks, when they become aggressive and are more likely leap from the nest when approached.
The chicks will fly when they are about 7 weeks old, but they will stay in the area with their parents until sometime in August, French said.
The fastest animals on earth, peregrines can dive at 240 mph and are deadly efficient hunters. Overall, peregrine have preyed on about 85 species of birds in Massachusetts and two or three bat species.
Since spring 2012, birdwatchers and ornithologists from around the world have been able to view the adult falcons and their hatchlings via the Du Bois Falcon Cam, a live stream of the nest, at https://www.library.umass.edu/falcons