Changing waterfowl require greater understanding

The latest review of waterbird populations in the UK makes interesting reading. At first glance it suggests contrasting fortunes for many of the species with which we share these islands. The review, jointly published by the BTO, RSPB and JNCC, stems from the efforts of some 3,000 volunteer counters. These volunteers participate in the synchronised monthly counts that take place across our many inland and coastal waterbodies.

While some species reached new ‘highs’ in terms of their population levels, others reached all-time lows. An examination of the ‘winners’ and ‘losers’ reveals that many of the ‘winners’ are introduced species whose naturalised populations continue to expand. These include Egyptian Goose, Mandarin Duck and Barnacle Goose. However, in with these are genuine colonists like Little Egret, a species expanding north on the back of global climate change.

The numbers of some species reflect breeding conditions elsewhere, the UK being a wintering ground with little or no breeding population of its own. A poor breeding season elsewhere may see fewer birds available to make the journey to our shores. The recent downtown in wintering numbers of Bewick’s Swans was once thought to be linked to a contraction eastwards in the wider European wintering range. However, recent research has revealed a decline in the overall population rather than just a shift in distribution. In contrast, our population of wintering Whooper Swans has continued to increase, with most of our visiting Whoopers arriving from Icelandic breeding grounds. The nature of the survey also enables the volunteer counters to gather information on breeding success for some species. In the case of the Whooper Swan, cygnets accounted for 16.8% of the birds present, slightly up on the previous winter.

The estuaries around Britain & Ireland are important wintering sites for many wading birds and these are also surveyed by the volunteers. Again fortunes appear mixed, with some notable increases seen in Avocet (a real conservation success story), Grey Plover and Sanderling. Balanced against this is the apparent news that Ringed Plover and Dunlin have both hit all time lows. Britain has eight sites of international importance for Ringed Plover but, while the decline might seem worrying, news of increasing numbers at sites elsewhere in Europe (notably The Netherlands) suggests that what we are actually seeing is an eastward shift in the core wintering range, perhaps linked to a run of mild winters.

Taken as a whole, this report highlights the need to monitor the changing fortunes of these birds at a much wider spatial scale, since a decline here may not mean that the population is falling, merely that it is now wintering elsewhere. Fortunately, our knowledge of waterbirds is increasing, placing our understanding into a wider context.

A bit of added colour

Bright and colourful, the Mandarin Duck is a species that is evidently exotic in origin. First introduced into Britain before the middle of the Eighteenth Century, this delightful little duck has now established a sizeable feral population. The current population, with its strongholds in Berkshire, Surrey, Buckinghamshire, Somerset and Gloucestershire, most likely is the result of escapes and introductions that took place during the first half of the Twentieth Century. Typically secretive in habits, the Mandarin appears to have established a population numbering several thousand individuals, virtually unnoticed. Perhaps this is not the only reason why the Mandarin has not attracted our attentions in quite the same way as certain other exotic waterfowl. There have been no obvious conservation problems associated with its arrival. In fact, up until recently, it was thought that Britain held a sizeable proportion of the world population, with numbers in the native Asian range believed to be in severe decline. Fortunately, new estimates of breeding numbers in China, Japan and Korea suggest that the species is doing rather better there than previously supposed.

I remember seeing my first Mandarin whilst undertaking a hiking expedition towards one of my Cub Scout badges. To see such a brilliantly coloured bird (it was a male) on a tiny stream running through a block of woodland was a revelation. Here was a bird that looked even more stunning in the flesh than in those of my bird books which sometimes over-egged plumage colours. Since that first encounter I have stumbled across Mandarins on a fairly regular basis, though less so within Norfolk.

This pattern of encounters seems to be changing and, since 1995, the species can no longer be considered scarce within the county. Pairs have been reported breeding in Norfolk since the 1960s and there have been a number of high profile releases or escapes of birds, most notably at Sandringham where eight ducklings obtained from Windsor were released in 1973. A look through Norfolk Bird Reports supports the nortion that there has been a notable increase in sightings since 1995, with some sites now just about guaranteed to ‘deliver’ the species for the birdwatcher. Top amongst these has to be Felbrigg Hall, where a dozen or so individuals may be seen on the lake at this time of the year. Interestingly, these little ducks do not gather in large flocks, even though they are largely sedentary in nature. Nesting in tree cavities and feeding throughout the winter on tree seeds (such as beech mast and acorns), the grounds of Felbrigg must be a rather favourable habitat for Mandarins. If you get a chance to visit them, please do and add a splash of colour to a dull January day.