Condition and age structure of bird populations on the Mersey : a report by the British Trust for Ornithology in association with the Merseyside Ringing Group and the British Association for Shooting and Conservation to the Mersey Oil Spill Project Advisory Group in fulfilment of Contract 3B /
Clark, N. A.
Evans, J.
Lochhead, D.
British Trust for Ornithology.
Tring : British Trust for Ornithology,
1992.
"August 1990".