During the 1990’s data were collected in Scotland on the ranging behaviour of resident golden eagles. Analyses of these data produced a model that predicts likely eagle ranging behaviour based on location and use of nests, nearness of neighbours, terrain, and land cover (McLeod et al 2003). This ‘PAT’ (Predicting Aquila Territories) model was explicitly developed to assess likely development impact on range use by eagles (Whitfield et al 2001, McLeod et al 2003) and extended the ‘RIN’ (Research Information Note) model of McGrady et al (1997). Though they are no substitute for actual field data, these models have proven useful in assessing likely impact of developments within eagle home ranges, especially where high-quality local observational data are not available. Guidance from Scottish Natural Heritage on assessing effects of wind farms on birds recommends the PAT as a useful supplementary tool in investigating potential effects of developments on resident eagles (SNH 2004).
Working within a GIS environment with a minimum set of data, eagle range use can be predicted and the likely effects of development can be assessed relatively quickly. Variations in the size and location of developments can be examined in a near-interactive way to determine their relative likely impact. Similarly, the effects of habitat management and other mitigation can be explored, and additional eagle field work, if necessary, can be targeted. PAT model products allow the likely effects of developments on eagles to be explored early in the development stage, improving design iteration and cost efficiency.
Minimum data requirements
Location of territory centre for eagle range in question and its neighbours.
Digital elevation data for the area.
Land cover data
Map of development
The PAT model uses the estimated location of home range centres of territory-holding eagles, terrain features and habitat information to predict areas likely to be important for territorial eagles. It can be used to assess the likely impact of developments, including windfarms, hydro-electric schemes and new forestry on range-holding eagles.
McGrady, M. J., McLeod, D. M., S.M Petty, J. R. Grant, I. P. Bainbridge. 1997. Eagles and forestry. Forestry Commission Research Information Note. No. 292. HMSO. London.
McLeod, D. R. A., Whitfield, D. P., McGrady, M. J. 2003. Improving prediction of golden eagle (Aquila chrysaetos) ranging in western Scotland using GIS and terrain modelling. J. Raptor Research 36(1 Supplement): 70-77.
McLeod, D. R. A., Whitfield, D. P., Fielding, A. H., Haworth, P., McGrady, M. J. 2003. Predicting home range use by golden eagles Aquila chrysaetos in western Scotland. Avian Science 2: 183-198.
SNH 2004. Survey methods to assess the impacts of proposed onshore wind farms on bird communities, SNH Guidance Note, SNH, Edinburgh.
Whitfield, D. P., Band, B., McLeod, D. R. A., Fielding, A. H. 2001. Predicting the effect of wind farms on golden eagles in Scotland. Abstracts of 4th Eurasian Congress on Raptors, Seville, Spain. 25-29 September 2001.
Photos: M. McGrady