First Guillemot eggs seen at Sumburgh Head

Published: 11 May, 2019

During the breeding season there is always a lot of auk activity down on the stacks and the lower ledges. This last week we’ve been keeping an eye on the cliffs for our first glimpse of on egg and we didn’t have to wait long. On Thursday morning, about 7:30am SOTEAG Seabird Monitor, Will Miles reported seeing the first Guillemot eggs on the ledges beneath View Point 2.

Like all our breeding auks, Guillemots lay just one egg and theirs is a most intriguing egg being highly colourful and uniquely conical in shape. Guillemot eggs are unique in colour and surface pattern, ranging from speckled turquoise to pale brown. As Guillemots nest on crowded ledges, it is thought this variation of colour and pattern allows parent Guillemots to recognise their egg.

There are various theories to explain the curious shape of a Guillemot egg. It has been suggested that the conical shape maximises heat transfer from the parent during incubation, as the narrow end points towards the tail feathers while the rounded part fits snuggly under the  parent’s warm belly. However, if this was the optimum design for incubating a single egg then why are Razorbill eggs a different shape? Perhaps their nesting site also has the answer: Guillemots choose to lay their eggs on narrow sloping ledges, so it has been suggested that the conical shape of their eggs helps fix them to the ledge – a property that isn’t required for Razorbill eggs as the parents often tuck themselves inside little crevices at the breeding colony.  

Follow our Sumburgh Head Lighthouse Facebook page to see how the season progresses for our Guillemots, Razorbills and Puffins. You can also find out more about these awesome auks in our Marine Life Centre.