Manx Shearwater Vs Guillemot: Key Differences Explained

Both the Manx Shearwater and the Guillemot are seabirds that can be spotted off the coast of the UK. These two species share enough similarities to make it difficult to tell them apart from a distance.

They both have black backs, white bellies and a similar shape especially when observed flying and they can both be seen all around the UK at various times of the year.

Keep reading to find out more about these interesting seabirds as we find ways to differentiate between the two species.

Table of Contents

Key Takeaways

When seen on land, guillemots look like penguins
Manx shearwaters are considerably smaller than guillemots
Manx shearwaters have a light stripe that runs through their eye
Guillemots have a white ring around their eye and a stripe behind it
Manx shearwaters nest in burrows or under huge rocks
Guillemots nest on cliff faces

What Is The Difference Between Guillemots And Manx Shearwaters?

Guillemots and manx shearwaters have a number of things in common which can make identifying each species difficult. Especially if you’re observing from a distance and there are a number of species in the same location.

However, these bird species have enough differences to make identification possible. Let’s start with the visual differences and see how many differences we can find.

Visual Differences

Guillemots are members of the Auk family and look distinctly like penguins when seen on land. They have a brown head and upper body with a contrasting white lower body.

In poor lighting conditions the guillemot’s brown head and upper body can look black if seen from a distance. The head, neck and long thin black bill all blend in together.

Guillemots are often mistaken for Razorbills; however, their colours and markings are quite different. When standing out of the water, guillemots take on the appearance of penguins.

Manx Shearwaters are relatively small for a shearwater and quite a bit smaller than guillemots with a shorter wingspan as well. Manx shearwaters have a black back, neck, bill and wings with a white under belly.

They have long narrow wings and streamlined bodies and a long thin bill. If seen close enough or through high powered binoculars, the light stripe that runs through the eyes of the manx shearwater is clearly visible.

Guillemots on the other hand have a white ring around the eye and a stripe behind it.

Differences In Habitat

Both of these birds spend most of their lives out at sea only returning to land to breed. Both species can be spotted off the UK coastline with guillemots present all year while manx shearwaters are only present from March to October.

Guillemots nest on coastal cliffs mainly in the north of England and in Scotland. But they are present in many coastal areas all around the UK during the non-breeding season.

Manx shearwaters nest around the coasts of Wales, Ireland, Scotland and the Isles of Scilly. After the breeding season has ended they fly to warmer climes in places like South America.

Nests & Eggs

Manx shearwaters nest in burrows and under large boulders and only return to their burrows under the cover of darkness to avoid predators like great black backed gulls and great skuas. They will typically breed on islands that are free from any rats which are known to steal their eggs and take their chicks.

Guillemots are a peculiar bird, they don’t make any nests at all. They lay a single egg directly onto bare rock on the side of a cliff. Their eggs are pyriform or pear shaped and roll around in a circle if disturbed instead of rolling off the edge of the ledge on the cliff.

The eggs of the guillemot are white, pale or dark blue or green and often match the colour of the area of rock they have been laid on. They often have markings that can include dark spots, freckles, blotches or thin lines. The size of a guillemot’s egg is around 82 x 50 mm and weighs around 108 g.

Manx shearwaters also lay one egg which is white and is around 61 x 42 mm in size and weighs around 57 grams. Manx shearwater eggs are rarely seen as they are laid underground in burrows or under huge rocks and boulders.

Likewise, guillemot eggs are also rarely seen as they are laid on cliffs within huge colonies of other cliff nesting birds. The guillemots eggs are often covered in the bird’s excrement which helps camouflage the egg and keep it in place on the edge of the cliff site.

Bird Calls

These two bird species have totally different calls which can help to determine which birds you’re watching. Manx shearwaters are mainly vocal at night especially in their breeding colonies.

You will hear an almost scary mix of wails and coos which gave them the nickname in days gone by of “devil birds”.

Guillemots are more vocal during daylight and you will often hear a deep murmuring or muttering sound coming from guillemot habitats.

The use of these bird calls is vital in both species for communication and socialising and is especially present during the breeding season.

Size & Weight

One big difference between manx shearwaters and guillemots is their size and subsequent weight. Manx shearwaters are far smaller than guillemots with an average adult manx shearwater weighing around 350 to 450 g with a body length of around 30 to 38 cm and a wingspan of around 76 to 82 cm.

Guillemots weigh twice to three times as much as manx shearwaters on average with a weight of around 850 to 1,130 g with a body length of between 38 to 45 cm and a wingspan of around 64 to 73 cm.

Guillemots are similar in size to gannets while manx shearwaters are similar in size to common terns.

Frequently Asked Questions

What does a Manx shearwater look like?

Manx shearwaters are small members of the shearwater species and have slim wings that are black above and white below and a streamlined body which is also black above and white below.

What do guillemots look like?

Guillemots are slightly larger than a razorbill and have a brown head and upper body with a white under belly. However, when seen from a distance the brown head, neck and back look black.

What is the nickname of the manx shearwater?

Manx shearwaters were originally called “Manks Puffins” during the 17th century. However, their modern nickname is the “devil birds” due to their eerie bird calls typically heard at night.