Consultez les articles du Bulletin Aves !
Aves, 10/1 | 1973 | 19-25
During tree pelagic cruises in the South-eastern part of the North-Sea, the author spent a total of 82 hours (in 41 days) watching birds (Joiris, 1972). Sea bird watching involves only few birds, belonging to non-marine species. Nevertheless, it is a mathod which enables to point out periods of movement for given populations.