Almost There

The finished nest should have the following features:

A depression where the eggs will lay. In the final nest building stage, the depression will be lined with softer material like grass and down from the swans to cushion the eggs.  I have noted the female plucking down during the past couple of days, so we may be nearing completion.

Sloping sides, to allow easy access to the nest for the cygnets and also allowing for  eggs to be pushed back into the depression should they fall out.

The nest has to be high enough to prevent water from getting in and swamping it.ensure

As a protective measure against mammalian predators, the moat or ditch will surround the nest.

The final size of the nest depends on the amount and type of nearby material.

Also, if there is a lot of material around the nest site. The final nest will be larger it will be added to during the incubation process.