5 Great Migrations
Dec 13 2024
The waters around the Hebrides are incredibly productive but are also very seasonal. A lot of the species we see here every day in the Summer are only around for a short period of time. We even have a few rarer visitors that you might not expect to find in Scotland!
1. Manx Shearwater
Each Spring on the Isle of Rum, a cloud of up to 120,000 Manx Shearwaters (Puffinus puffinus) descend on this small isle. Manx Shearwaters are a bit like puffins, in that they produce a single chick that lives underground in a burrow. However, they have a unique migratory behaviour. When the chick is almost fully developed the parents will fatten it up until it weighs more than they do and then they take off, leaving the chick alone. This little one will then spend the next week looking at the sky and mapping the stars – a process known as astral imprinting. Ready to go, under the cover of darkness these fledgelings will then fly across the Atlantic, until they reach South America where they will spend their juvenile and sub adult years. After roughly 6 years, 80% of the world’s population of Manx Shearwaters will then journey back to the UK, navigating by use of the stars, returning to the exact spot that they were born.
2. Orca
Orca or Killer Whales (Orcinus orca) are highly intelligent, social animals with often complex or unexplainable behaviour – such as the pod which developed a trend of wearing salmon hats, and our two resident boys are no different. John Coe and Aquarius have a cult following here on the west coast, with a large network of citizen science reports any time they’re sighted and they’re often seen covering huge distances in short periods of time for unknown reasons. These two bull orca used to be part of a larger pod known as the West Coast Community pod but as of 2016 following the loss of the last female, Lulu, it seems that these two are the last remaining members. Maybe they’re looking for some new company?
To get an idea of the distances travelled over such short timeframes, John Coe’s distinct dorsal fin was photographed as the pair were seen in Cornwall on the 5th May 2021 and then were both resighted off Skye on the 14th May, meaning they covered an average of 100km a day! Just this year they’ve been sighted as far south as the Blasket Islands in Ireland and all along the Scottish coastline from Eyemouth on the east coast, to the Western Isles of Lewis, Skye, Coll, Tiree, and were even spotted travelled up through the Sound of Mull. All this travelling makes them super unpredictable so you never really expect to see them until they’re right there in front of you!
3. Arctic tern
Covering up to 1000 miles a day and travelling from pole to pole, the Arctic Tern (Sterna paradisaea) holds the title for the longest migration on Earth.
Each Spring we see arctic terns return to nest and raise their young. These delicate looking birds have just returned from a Summer in the Antarctic circle, ready to take advantage of another seasonal bloom of prey. In a straight line the distance is 18,500 miles, but since they don’t fly in a straight line the estimate is 22,000-28,000 miles for each leg of their journey. Based on these numbers an adult tern can reach well over 1 million miles over its 30-year lifespan.
4. Leatherback Turtle
An unusual species and not one that we see very often. As the name suggests, leatherback turtles (Dermochelys coriacea) have flexible leathery shells whereas other species of marine turtle have solid shells. They are also unique among reptiles as they can raise their body temperature above that of the surrounding water. This allows them to survive our climate as they search for their favourite food, jellyfish, of which we have plenty!
Leatherbacks nest on beaches in the Caribbean and in West Africa and its thought they follow the warmer waters of the gulf stream to the UK as part of their 12,000 mile round trip. Despite their measuring over 2m in length and weighing 600kg they’re incredibly elusive animals. These ancient reptiles can hold their breath for up to 85 minutes and have been recorded diving to depths of 1200m, so to spot them you really need to be in the right place at the right time and looking in the right direction!
5. Cetaceans
Some of the most common cetaceans seen on our trips are the aptly named Common Dolphin (Delphinus delphis), and the smallest of the rorqual whales, the Minke whale (Balaenoptera acutorostrata). Of the North Atlantic population of 600,000 common dolphins most live further south, along the coast of continental Europe. However, we have a steady population of around 500 around the Isle of Coll which we see frequently in varying pods sizes of anywhere from 5-300 individuals. Minke whale sightings usually vary year on year, but it’s estimated that 1/3 of the North Atlantic population come to the west coast of Scotland each Spring.
Despite being so common we still know little about where they spend the winter months. It’s thought that both species may head offshore and travel south to the Azores but there’s no confirmed evidence for this theory, and some sightings persist into the winter. It’s hard to know for sure how many individuals remain around our coastline, as most operators stop for the winter due to less tourism and rougher sea conditions.
In recent years the numbers of common dolphins and minke whales have both significantly increased making them a welcome sight on most of our days offshore!
