Diving mallard

There is just one female on site so far this breeding season (pictured). As discussed in previous blog entries she has been the subject of heavy competition between two drakes although that particular situation seems to have calmed down over the last week or so. However she has a peculiarity that I have not previously observed with adults mallards - she spends a lot of time diving for food. All mallards dabble - that's when they stick their heads under the water and use their feet to keep themselves facing vertically down. Also the ducklings go through an entertaining phase when they dive under water and then bob up like corks. However she has been regularly diving for food whilst her accompanying drake continues to dabble. It seems that this behaviour is seldom seen with mallards. My theory is that she was brought up on the moat ( I have always assumed that the ducks that breed here are from the ones previously raised here) and learned the behaviour from the Tufted ducks that were here last year which are proper diving ducks.