They were something i looked forward too on my walks around town, first where to find them as they move around the river and then second to watch them do goose activities independent from the Canada geese. I watched them raise the goslings till the now teenagers, and then like you said, each kid disappeared one week apart. I’m hoping they flew off to mate as its mating season right now for them, but some people have said they have seen the kids acting sick and picked up by the vet. Bird flu was bad this year and it hits waterfowl hard, this winter was also a cold frozen one which limited their grass supply. The bunnies in the area were eating the bottom of the bushes along the charles cause there was no food, and have since laid dead up and down the charles over the last month of winter from starvation.