Méndez, V., Austin, G.E., Musgrove, A.J., Ross-Smith, V.H., Hearn, R.D., Stroud, D.A., Wotton, S.R. & Chas A. Holt, C.A. 2015. Use of environmental stratification to derive non-breeding population estimates of dispersed waterbirds in Great Britain. Journal for Nature Conservation doi:10.1016/j.jnc.2015.09.001