SummaryThe Fulmar has a long period at the breeding colony prior to egg‐laying. The pattern of annual occupation and build‐up in numbers has been examined in detail at Marsden, Co. Durham, at a colony in which over 100 eggs are laid annually (Order 3 of Fisher's classification).The re‐occupation of the cliff starts in early November with an occasional visit by one or two birds. The main period of activity at the cliff is during the morning and, as the numbers build up, the diurnal period of occupation increases. By mid‐December the first birds to arrive in the colony do so before dawn and the last to leave remain well after dark until near midnight. Almost throughout the pre‐egg stage, the colony is deserted each night and re‐occupied the next day and birds only stay regularly overnight just before egg‐laying. A similar pattern of occupation occurs after breeding but in the reverse order.The numbers of birds at the colony in January and February exceed the breeding population and include many non‐breeders. The non‐breeders progressively decline in numbers until May when only the breeding birds remain with a few non‐breeding birds.The daily variation in the numbers of birds at the cliff is influenced by the wind speed. In general, the birds leave the colony under freshening conditions and the number present at the colony can be interpreted in terms of the wind conditions over the last three days.It is suggested that the synchronised departures are primarily feeding trips, the birds using the strong winds to reach feeding areas, except that the departure just before egg‐laying is linked to egg development and synchronised laying in the colony.Competition between Fulmars and Kittiwakes for nesting sites usually results in the Kittiwakes gaining the site. This is achieved by the Kittiwakes taking over the Fulmar sites during one of th