During the last two bird surveys on ’98 land, I have come across a mallard nest on the banks of the Bourn Brook. On the, 27^th April, the female flew off the nest site which was very close to the route I was taking along the bank, and there were four eggs.

She flew to a spot on the brook where two male mallards were waiting, and they all flew off together; indicating that the female may still have unfertilised eggs that these males were hoping to help with - mallards have interesting lifestyles!

On the visit on the 5^th May the female was still on the nest, and now there were six eggs, so clutch-building is complete and she is undertaking incubation. The males were nowhere to be seen.

In some mallards, a pair stays together even during incubation and hatching, but quite often the female goes alone. Her drab brown plumage makes sense for doing all the incubation, while the colourful males would draw attention to the nest if they got involved in that important business.

It seems like mallards are increasing in the area and successful nesting is of course fundamental to any chance of a bird species increasing the population. While mallards have many predators during nesting – foxes, crows, stoats, and many more – the lack of any mink in recent years will almost certainly have had a massive impact on increasing success rates.

Mink particularly hunt the areas where mallards hang out, and of course they are also very capable of taking the ducklings even if the nest and eggs aren’t found during the incubation period. One of the first mink I saw in Cambridge was about 25 years ago, when I was on a punting trip on the River Cam. A mink attacked a brood of ducklings, many of which actually jumped into our punt to escape! The mink caught one and went off with it, but of course it would know that there was a reliable source of food in that area and come back for the rest later.

Mallard populations in the UK have increased over the last 50 years, but in the last 20 years the numbers have stabilised and started to decline. According to the British Trust for Ornithology, little is know on the causes of change. It has been placed on the ‘Amber List’ of Conservation Concern, mainly due to declining winter numbers, but this could be because fewer European birds are visiting the UK in winter as climate change expands the area they can spend their winter months. It is such a mundane species that it rarely receives attention! It will be interesting to see if or wider efforts to eradicate mink across East Anglia have detectable impacts on mallard at the regional scale – there is enough monitoring data to detect this over the next few years.

Dr Vince Lea
Head of Wildlife Monitoring