Because the town is unusually well watered, and because a lot of that water sits next to mown grass that people use.
Berlin's adopted 2023 Plan of Conservation and Development names the Mattabessett River, Belcher Brook, Crooked Brook, Hatchery Brook, Spruce Brook, Webster Brook and Willow Brook as the major watercourses. On the still water side it names Silver Lake, Upper and Lower Hart Pond, Paper Goods Pond, Railroad Pond, and the Hallmere, Merimere and Kenmere reservoirs. That is a long list for one town.
The same plan counts 628 acres of recreation facilities, split as 474.3 active acres and 120.4 passive, and that figure excludes conservation land. Add 348.3 acres at Timberlin Park and 77 acres at Sage Park and the shape of the problem becomes clear: a lot of maintained turf, a lot of water, and in several places the two are adjacent.
That adjacency is the whole thing. Connecticut DEEP describes the habitat that holds resident Canada geese as lawn beside water. Short irrigated grass is better food than anything in a hedgerow, the open sightlines let a bird see what is coming, and water a few steps away is an escape route. A goose does not need a property to be neglected. It needs it to be exactly what a playing field or a golf course is.
What Berlin does not have, on the record, is a documented town goose program, complaint file or news report to point at. We would rather say that than borrow a statewide fact and dress it up as a Berlin incident.