A fair number of guillemots nest along the Dorset coastal cliffs and, if you look carefully, amongst them you will find a lesser number of of their cousins, razorbills (Alca torda). They are not easy to get close to from the heights of the cliffs as they nest on the lower edges and this photograph I took is about as good a view as I have ever been able to get. It does show the two features, however, that enable you to pick them out from amongst the many guillemots.
Firstly, and usually the most obvious feature, is the razorbill's razor bill! The guillemot has a much more pointed bill whereas the razorbill has a much bigger, chunkier, awkward looking beak. The other feature, when the light is good, is that the razorbill is very much darker, almost black, on its back whereas the guillemot is chocolate brown.
The two species are both members of the Auk family (along with puffins of course) and they are often seen together and so obviously get on well together. In many ways they are the penguins of the northern hemisphere