Guillemots are spring and summer visitors to the Southern Hebrides and by far the biggest gathering of one species is the colony of guillemots at Harp Rock on Lunga in the Treshnish Isles.
Guillemots nest and breed on extremely narrow ledges on the sheer cliffs and huge numbers, as many as 5000, are crammed together onto this inaccessible rock rearing their chicks (jumplings). When they are ready, the jumplings leave the nest and are looked after by the males for 4-6 weeks.
One outstanding ability guillemots have is they can dive to incredible depths in search of food, a trait they share with razorbills. One has been recorded at a depth of almost 90 metres at the base of an oil rig in the North Sea.