This manual is a product of a course in methods for counting waterfowl in aeroplane and ship organized by IWRB's Western Palearctic Seaduck Database and Nordic/Baltic Duck Survey Group in collaboration with Britain's former Nature Conservancy Council, and arranged by Denmark's National Environmental Research Institute.
Manual for Aeroplane and Ship Surveys of Waterfowl and Seabirds
Komdeur, J.; Bertelsen, J.; Cracknell, G. (1992). Manual for Aeroplane and Ship Surveys of Waterfowl and Seabirds. Report by National Environmental Research Institute (NERI). pp.