Before a nest exists, and before the swimming season sets the calendar for you.
Connecticut DEEP puts territorial defense as early as March and nesting by early April, with incubation running about 28 days and young hatching through to June. Up to that point a shoreline is just a shoreline. Once a pair is holding ground, the situation becomes a protected-nest problem and what anyone may lawfully do nearby narrows a great deal. On a site with a public beach, that also happens to be the period when the ground is quietest and easiest to work.
Then the recreation season arrives and inverts it. Swimming, fishing and the general public presence at a pond like Eastbury put people on the exact ground the birds are using, at the exact times a program most wants access. Work that could have been done comfortably in March becomes a scheduling negotiation in July.
The winter half has its own logic here. Skating means the site stays in use when most properties have gone quiet, and DEEP's statewide timing has migrants arriving in early October, movement continuing through November with another peak in mid-December, and most birds leaving by mid-January, though mild winters hold them longer. A flock that settles in over the cold months is the flock you meet again in March with a fixed opinion about the place.
Two dates are worth treating carefully here. Nobody publishes when a Glastonbury pond freezes or opens, so we watch the water rather than the calendar. And on a drawdown pond like Great Pond, where the level moves substantially across the year, the shoreline itself is a moving target, so a plan drawn in one season should be checked in another.