Arctic Skua Vs Pomarine Skua: Key Differences Explained

Arctic Skua Vs Pomarine Skua: Key Differences Explained

It can be difficult to differentiate between the 3 smaller species of skuas. The Arctic skua, pomarine skua and the long-tailed skua all look very similar especially if spotted flying out at sea.

There are differences between these birds. However, they are  subtle and to the untrained eye can be difficult to spot. In this article we’ll take a closer look at the arctic and pomarine skuas and identify all of the differences to make it easier to spot these birds when out birdwatching.

Keep reading to find out more.

Key Takeaways

  • One of the easiest ways to differentiate between arctic skuas and pomarine skuas is that pomarine skuas have spoon shaped central tail feathers
  • Pomarine skuas also have low hanging bellies
  • Pomarine skuas tend to nest in north Russia, north Alaska and northern Canada
  • Arctic skuas tend to nest in the west and north of Scotland and the Scottish Islands
  • Both of these birds have very different tactics for getting food with pomarine skuas being far more physically aggressive than arctic skuas who tend to just use intimidating flying tactics

What Is The Difference Between An Arctic Skua And A Pomarine Skua?

Although these two bird species share many characteristics, there are enough differences to make a fairly informed identification even at a distance. However, as both of these birds go through various phases, identification of an individual bird can be challenging.

For instance, all skuas go through a dark phase and a light phase when their plumage changes colour completely. Plus juveniles of both species look very similar. Which means in some cases, all you can say is that the birds you’re looking at are of the skua family.

With all that said, let’s start looking at the distinguishing features of both the pomarine and arctic skuas.

Visual Differences

Let’s look at the visual differences between arctic and pomarine skuas.

Pomarine Skuas

Pomarine Skua

Of the three smaller skuas, the pomarine is the largest and heaviest and is only slightly smaller than a herring gull. The pomarine has been described as “full bodied” and having its centre of gravity between the breast and belly.

You can often identify a pomarine skua by its low hanging belly. This is quite similar to the great skua, however, the pomarine has a smaller head, a longer tail and its body isn’t as barrel shaped as the great skua.

Adult pomarine skuas also have spoon shaped central tail feathers. They also have a black crown and face mask and their bill is flushed with a dull shade of pink and tipped with black.

They have pale yellow cheeks, throat and neck, a bright white belly with a dark grey breast band (although this can’t be relied on as it is always present in females but is often missing in males, but not always).

Their backs are a dark grey colour which is also found on the wings and tail with white flashes on the underside of the wings and a white patch on top of the wings.

Dark Morph Birds

However, not all adults are coloured in such a distinguished way. Around 20% of all pomarine skuas are what are known as dark morph birds.

These dark morph pomarine skuas have a deep almost black plumage all over their bodies with the base of their bill a grey colour. But they still have those white wing patches.

In many ways these dark morph colourations make the birds seem more intimidating.

Arctic Skuas

Arctic Skua Flying

Adult arctic skuas also have a dark phase and a light phase which can make differentiating between the two difficult. The light phase birds have a white belly, and a dark back and cap.

The dark phase is dark brown all over. An easy way to distinguish between arctic skuas and pomarine skuas is by looking at the tail feathers. Arctic skuas have two pointed central tail feathers that protrude beyond their main tail.

They also have broad white flashes on the underside of their wings. 

While on the subject of wings, arctic skua wings are more elegant and not as wide as those of the pomarine skua.

Differences In Habitat

Both pomarine and arctic skuas spend most of their life out at sea which in birding terms means they are pelagic. When the adults reach sexual maturity both arctic and pomarine skuas return to land to breed.

They both scrape out shallow depressions in the ground which are lined with local plant materials.

However, there are differences in their breeding habitats;

Pomarine Skuas are typically found in the tundras of northern Russia, northern Alaska and northern Canada during the breeding and nesting season.

They prefer areas with moist boggy land or mossy ground. They over winter out at sea but relatively close to the coasts of all major continents. 

But are typically found between the tropic of cancer and the equator and around the Australian continent during winter months.

Arctic Skuas are typically found in the far north and west of Scotland and the Shetland and Orkney Islands when breeding. They are typically found nesting on moorland and marshland with their nests often situated on a mound with a clear view of the sea. 

Arctic skuas migrate to South Africa and South America during winter months.

Can You See Arctic & Pomarine Skuas In The UK?

In all honesty, you’re more likely to see arctic skuas in the UK than you are pomarine skuas. This is because arctic skuas breed in the west and north of Scotland and the Scottish islands.

Whereas pomarine skuas typically only enter UK coastlines during their winter migration and only then if they happen to get blown off course.

Nests & Eggs

Both arctic skuas and pomarine skuas make shallow scrape nests which are basically depressions in the ground. The nests are typically situated in colonies with other birds of the same species.

The shallow depressions are scraped out by both parents and then lined with plant material that’s found in the local area.

The eggs from both arctic skuas and pomarine skuas are of similar colours; dark olive brown with darker brown spots or freckles.

Pomarine skua eggs are around 73 x 48 mm in size whereas arctic skua eggs are around 58 x 40 mm in size. So pomarine skua eggs are larger than those of the arctic skua.

Differences In Feeding Habits

Arctic skuas are adept at intimidating other birds into dropping their regurgitated food and then stealing it for themselves and their young. The pomarine skua is equally as fast and skilled when in flight.

However, pomarine skuas tend to use more brute force when trying to intimidate other birds to give up their food. Pomarine skuas will also be more likely to be found sitting on the surface of the sea with other seabirds waiting for fish.

Bird Calls

These two skuas can also be identified by their differing calls. Arctic skuas make a distinctive nasal mewing sound which is often heard during their aerial displays when intimidating other birds to give up their food.

They can also make a sharp alarm-like sound if they feel under threat.

Whereas pomarine skuas are not particularly vocal. The males tend to make wheezing sounds as part of their courtship displays and females make a growl-like sound when they feel threatened.

Pomarine skuas also make  a long series of around 15 gull-like sounds as well as a sharp two noted alarm call that sounds like “which-yew”. This is particularly common when out at sea and threatening other birds to drop their food.

Size & Weight

Pomarine skuas tend to be larger and heavier than arctic skuas with pomarine skuas being around 46 to 51 cm in length with a wingspan of around 113 to 125 cm. Pomarine skuas weigh in at around 550 to 900 grams.

Arctic skuas on the other hand, tend to be around 40 to 45 cm in length with a wingspan of around 110 to 125 cm and weighing around 330 to 570 grams.

SEE ALSO: Aquatic Warbler Vs Sedge Warbler: Key Differences Explained

Frequently Asked Questions

Are Arctic and pomarine skuas the same?

No, arctic and pomarine skuas are not the same. They are both members of the skua family but they do have striking differences.

What are the differences between arctic skuas and pomarine skuas?

One of the main differences between pomarine and arctic skuas is the tail feathers. Adult pomarine skuas have spoon shaped tail feathers, arctic skuas do not have this feature. Also adult pomarine skuas are larger and heavier than arctic skuas.

Are pomarine skuas aggressive?

Yes, pomarine skuas can be aggressive especially when intimidating other birds to give up their food. Or when they feel threatened.

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