Friday was a big day for Mass Audubon’s South Coast Osprey Project, but an even bigger one for a dozen osprey chicks collected from various spots along the Westport River and put on a plane bound for Illinois.

The Audubon’s project, now in its fifth year, hit a milestone Friday when the 60th bird relocated to Illinois was collected, the Audubon’s Gina Purtell said.

The program, a collaboration among Mass Audubon, the University of Illinois and the Illinois Department of Natural Resources, seeks to restore osprey breeding populations in that state. While osprey have made a dramatic comeback in Massachusetts over the last 40 to 50 years, historic populations of the migratory bird are not doing as well in Illinois, and the species is listed as threatened there.

Audubon volunteers set out in small boats to several nesting platforms in the river Friday, collecting selected chicks along the way. When they’d gotten a dozen, they were brought ashore and from there taken to a field station set up for the day, where Purtell and helpers loaded them in her Subaru for a drive to the New Bedford airport. There, a small four-seater plane bound for Illinois awaited.

Purtell said this year’s 'translocation' went well, and she was happy to report that the Audubon’s work has been making an impact in Illinois.

This year, she said, Illinois officials confirmed that two chicks collected from Westport in 2020 returned to their nesting sites in Illinois, following their long winter migration to the south.

She was excited to learn the news, she said: “More of our birds could be there, but these two have made themselves very apparent.”

In addition, she said, she is delighted to report that a male osprey that hatched on the West Branch of the Westport River in 2020 is now raising a brood of five-week-old chicks.