Spatial attendance data for immature common guillemots (Uria aalge) at four sites in a large breeding colony

This dataset only presents the number of intervals that individuals spent in pre-breeding and breeding areas. Grid cells with ledges and no apparent evidence of breeding activity but consistent breeding activity completely surrounding them were also assumed to be breeding areas. Individual birds were identified using unique colour rings which were visible at a distance through a telescope with a x20-60 zoom lens. All data was collected by the same observer to ensure consistency.