Austin, G.E., Cook, A.S.C.P., Maclean, I.M.D., Mitchell, P.I., Rehfisch, M.M. & Wright, L.J. 2010. Healthy & Biologically Diverse Seas Evidence Group Technical Report Series: Evaluation and gap analysis of current and potential indicators for Seabirds & Waterbirds. JNCC, Peterborough.