This afternoon Zoe pointed out a strange grouping of ducks right in the centre of the largest of the Reading University lakes. There were about twenty ducks all swimming around in a circle no greater than about 2 metres in diameter. They seemed to be a mixture of males and females, the females being a drab light brown colour, but the males having black heads, a large white patch covering their breasts and shoulders, a large reddish-brown patch on their sides, and a smaller white patch under a black tail.
As they were a long way out and did not seem to be interested at all in the bread that we were throwing, so we could not get a close look at them. However, I am fairly confident that they were shoveler ducks (Anas clypeata). We were not able to clearly make out their characteristic 'shovel' bills, but when we go back tomorrow morning I will be taking my binoculars with me.
The densely-packed flock was probably feeding (BWP-CE states "Most likely to congregate densely when feeding" and also notes that they tend to gather in flocks of 20-30). They feed on small animals and plant debris that they suck up with their 'shovel' bills. The flock were probably swimming in a circle in order to create a whirlpool to stir up food from the bottom.
On Sunday, Zoe and I went back to the lake with our binoculars and this
time we could clearly see the shoveler's beaks. Most of them were formed into two densely packed
rotating groups. Occasionally one or two birds would detach
themselves from one group and swim across to the other. We later
noticed a more dispersed group of shovelers basking in the winter sun at
the other end of the lake.