Outdoors: 'All around Scotland, the skies are filling with geese coming home to roost'

It is confirmation, if it were needed, of the impending approach of winter. Spring seems a thousand miles away.

But this should only be a fleeting moment, for autumn is a special season heralded by an influx of geese to our shores with their honking V-shaped formations etching the morning and evening skies.

In global terms, Scotland is an incredibly important wintering ground for geese due to its proximity to core breeding grounds in Greenland, Iceland, Svalbard and Scandinavia, combined with our relatively mild oceanic climate, rich estuaries and plentiful inland feeding grounds.

Understandably, this international importance is not something all Scottish farmers are keen to celebrate because the birds can come into conflict with farming interests. Geese are the avian equivalent of the cow, prolific grazers that crop grass with real efficiency.

Geese can be fairly conveniently split into two categories - grey geese and blacks. The greys are by far the most abundant with the two most common being the pink-footed goose and the greylag. Both species will feed on farmland during the day and use traditional and well-established roosts at night, often on water - either fresh or tidal. Most of the greylags and pink-foots here have come from breeding grounds in Iceland, with a good number of pink-foots also arriving from Greenland. There is also a good breeding population of greylags in Scotland.

The east of Scotland is a real autumn and winter hotspot for these two species because of the abundance of farmland for feeding and estuaries and lochs for roosting. Some of the biggest concentrations can be found in Loch Leven in Kinross, which the birds use as both a roosting destination and a feeding area. In 1993, an incredible 27,300 pink-foots were counted at one reservoir roost in Fife.

Greylags and pink-foots can be difficult to tell apart. At close range the pink-foot has a darker head. The dark bill is also less prominent than that of the greylag, which has an orange beak. In flight, the greylag has a distinctive call, very much akin to that of the farmyard goose, while the equally vocal pink-foot has a similar but more "metallic" call.

Scotland hosts two other but much scarcer species of grey goose in winter. The Greenland greater white-fronted goose, which is characterised by a white band at the base of the bill, is a localised visitor to the Hebrides, Orkney and parts of south-west Scotland, with Islay being the principal haunt. Even rarer is the bean goose; a regular flock of about 250 birds winters each year on the Slammanan plateau in central Scotland.

In the black camp are the barnacle and brent goose. There are two distinct populations of barnacles - those from Greenland winter in the Outer and Inner Hebrides and Orkney, while birds that breed in Svalbard spend the winter in the inner Solway Firth. The smaller brent goose, which is not much bigger than a mallard, is usually seen on passage in autumn on its way to wintering grounds in England, Denmark and Ireland. The brent geese that pass through western Scotland to their wintering quarters in Ireland have come from breeding grounds in the Canadian Arctic - an epic 2,000 mile journey that takes them right over the Greenland ice-cap.

These two black geese should not be confused with the larger but similar plumaged Canada goose - an introduced species that breeds in several parts of Scotland, especially Perthshire and Dumfries and Galloway.

Thanks to our unique geographical location, the importance that Scotland holds for some of the world's goose populations cannot be over-stated. Our small country holds 50 per cent of the world's wintering pink-footed geese, 60 per cent of the Greenland greater white-fronted geese and 20 per cent of barnacle geese. Over 95 per cent of the Icelandic greylag population winters here. This is justification enough for their conservation, but another equally valid reason is the light that they bring to our dark winter skies.

This article was first published in The Scotsman on Saturday, 18 September, 2010