On the nest

Mr and Mrs Swan came back to the pools behind the office last week, having been out in th fields somewhere through the winter. Yesterday lunchtime both birds were on the other side of the road, but today they were back in the pool nearest my window. Their nest, half-hidden in the reeds, is in the same spot they used last year.
This bird appears to be sitting on eggs, so I guess they have been laid since yesterday. Both male and female mute swans (I think they're called that because they don't honk like most swans, they just make a nasal snorting noise and, if you get too close, they hiss) have a prominent knob at the base of the bill, as shown here. I presume this is the female because they do most of the incubating, although the males do take over for short periods.