POPULATION ESTIMATES FOR THE DUNLIN CALIDRIS-ALPINA DERIVED FROM REMOTELY SENSED SATELLITE IMAGERY OF THE FLOW COUNTRY OF NORTHERN SCOTLAND

THE Flow Country of northern Scotland is of international importance for wading birds, and has in the last decade been greatly affected by afforestation1, 2. Here we demonstrate that remotely sensed satellite imagery of this area can be used to make accurate predictions of the numbers of the dunlin Calidris alpina, and thereby assess the impact of forestry on this wading bird. The habitat favoured by dunlin is wet moorland interspersed with small pools ; they do not use large water bodies, built-up areas, woodland or agricultural land. We show first that the numbers of dunlin on 42 moorland sites, as surveyed in 1986 (ref. 3), are significantly negatively correlated to an index of soil wetness4, as provided by reflectance data from a satellite image of these sites taken in 1978 before afforestation. We then tested this relationship by using it to predict dunlin numbers on a random sample of unsurveyed sites. Subsequent surveying of these sites in 1988 revealed a good fit between predicted and observed numbers, and confirms previous independent estimates of dunlin loss4. © 1990 Nature Publishing Group.