What you may be observing is actually the female sitting intermittently on the eggs and then searching for the male. Depending on the species and individual attributes of the swan, usually, the male will not try to incubate the eggs, rather it is the female.

Whatever the case, one of the swans may have been chased or attacked by a predator and is refusing to return to the area. If the eggs hatch, the swan will care for the cygnets. Regardless, if there is a great deal of disturbance in this area (humans, predators, etc.), it is not likely that the swans will return to the area and try to nest again. The Regal Swan
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