Guillemots are the quintessential auks. They are colonial breeders nesting on the inaccessible ledges of sea cliffs & stacs. The single large egg is laid directly on stone & is pear-shaped so that if accidently dislodged it rolls in a tight circle reducing the risk of mishap.
A small percentage of Scottish Guillemots are of the bridled form -which have the appearance of wearing spectacles. The proportion of this form increases the further north the colony is.