As early as 1998, the World Meteorological Organisation and the UN Environment Programme had set up the Intergovernmental Panel on Climate change to investigate the claims of some scientists that the fossil fuel combustion was contributing to an accelerated warming of the planet. Few now question the validity of the science although specific outcomes remain the subject of much conjecture. In a montane environment, however, even small changes are magnified when combined with altitude; a rise in global average temperature of just 3 – 4 degrees Celsius could mean an upslope shift of habitats by up to 500 metres. And for species such as ptarmigan, whose range is restricted to the high coires and plateau, there may be nowhere else to go.
The ptarmigan’s problems don’t end there though. Dr Adam Watson, whose studies of ptarmigan in the Derry Cairngorm area of the Central Highlands have lasted for more than 50 years, points out that concentrations of walkers and skiers in some areas leads to increased chick and egg predation by crows. Scraps of food left behind by some of these mountain users attracts crows into places they wouldn’t normally be found and while there, they take advantage of any other opportunities to feed.
Fences are used extensively in downhill ski areas to assist in the accumulation of snow but research from Norway – and my own observations in Scotland – show that they too contribute to ptarmigan mortality. When the clouds are down and visibility reduced to a few metres, it’s not really surprising that deaths occur when these relatively poorly sighted, rather unmanoeuvrable birds whirr low and fast over the hillslopes.
NINA scientists, Dr Kjetil Bevanger and Henrik Brøseth, conducted investigations into the significance of reindeer fences in Finnmark, northern Norway, as a cause of death amongst resident willow (equivalent to the red grouse) and rock ptarmigan (Wildlife Biology 6:2 ;2000) . These structures range in height from 1 – 2.5 metres and are usually a combination of wire and mesh. Although the snow fences on Scottish hills are generally of closely spaced wooden paling and in theory easier for the birds to see and avoid, poor visibility negates this and indeed the Norwegians concluded that the height and type of fence had no effect on ptarmigan collision rates. They found that most mortalities occurred during the winter months (since most of the birds found in spring were in winter plumage) and that something between one and two ptarmigan fatalities per km of fence was “an absolute minimum”. While acknowledging that fences alone might not be pose a serious threat to ptarmigan numbers, when taken alongside the other pressures they experience – including poor breeding success in the unsettled summers associated with global warming – their significance rises.
It’s tough at the top…
Andy Raynor Dover NH