These are Mute swans that nest in several ponds located in a large municipal park near the shore of Lake Ontario.
Because these swans are not native to this region and compete with "local" waterfowl, their population is controlled
by workers from the NY State Dept. of Environmental Conservation (who kill the eggs by applying an oil coating).
Seems sorta sad, especially after observing the diligent nesting behaviors over a period of many weeks.