Mr and Mrs in the back garden

I had a shot last year of two ducks that frequented our front garden and grass - and they have returned.  At least I think that they are the same pair.

What fascinates me is their memory and I wonder about their longevity.

Anyway today they seem to have discovered the back garden, swooping in low and landing on the grass.  Willoughby appeared totally disinterested.  Size?  He wasn't prepared to say.