Great skuas have been painted as the villains of the piece for far too long. Dominic Couzens dares to find a sweeter side to these avian thugs.
There are some animals that wear their reputation. Look at typical pictures of great skuas, and you can guess what these sharp-clawed seabirds might be like. Bulky and aggressive, intimidating and uncompromising: if club bouncers were birds, they would probably be great skuas.
Most BBC Wildlife readers will have heard of the way in which great skuas (or bonxies, as they are known in Shetland) go about their business. They bully other seabirds into disgorging their catch; they attack and devour smaller birds and chicks; and, when not harassing other feathered creatures, they dive-bomb any humans and gormless sheep foolish enough to intrude upon their territories, sometimes even drawing blood with a savage peck to the head. It’s a sordid tale of abuse and brutishness.
But is this reputation deserved? Are great skuas just thugs that wreak a trail of violence across the boggy coastal moorlands and chilly seas that they frequent? Or is there maybe more to them, some hidden tenderness, panache or even a dash of vulnerability? In short, is there any beauty to detect within the beast?
Pirates of the high seas
Nobody could deny that great skuas are accomplished food-pirates, predators and scavengers. One of their favourite tactics is to steal from birds that are ‘bringing the shopping in’, returning from fishing trips with a fully laden bill or crop (the food storage area located just above the stomach in some birds).
The skuas’ main victims are guillemots and kittiwakes, which usually regurgitate their crop contents at the slightest hint of trouble. It is hard not to sympathise with these hard-working parents, which may have flown anywhere between 50km and 100km, only to surrender their prize at the final hurdle.
Food piracy, or kleptoparasitism as it is known, isn’t always so simple, though. Great skuas target gannets, too, which are a much better match for them and more than capable of defending themselves.
Such dogfights often end with the skua grabbing the poor gannet’s wingtips, causing it to stall and topple headlong into the sea. It’s a bold and skilful feat, and you have to admire the chutzpah. Besides, the skuas don’t always win.
Earning an honest living
Moreover, you often get the impression that skuas do nothing in the breeding season except pilfer and pillage, and this isn’t true. Surprisingly, they do a great deal of their own foraging. They pitch into mêlées of seabirds to seize shoaling fish from the surface of the sea, and refrain from directly abusing other foragers.
They do the same near trawlers, scrumming for discarded fish and fish parts, mucking in with robust equality, shoulder to shoulder with gannets, fulmars and gulls, shoving their competitors like bargain hunters at a closing-down sale.
To my mind, the skuas’ behaviour in these circumstances is no more sinister than starlings bickering over grub-digging spots on lawns – like everyone else, they have a living to make. By contrast, predation might seem fairly straightforward: one bird eats another; killer and killed.
Here, then, if we are to appeal on behalf of great skuas, we must search for something other than skill in order to stand up for their good name. So, how about their powers of learning?
Brutes with brains
It turns out that great skuas are predators with brains. This is best illustrated by the different patterns of predation seen in different skua colonies. Adult kittiwakes are relatively safe on the island of Foula in Shetland, but further north, on Hermaness, they must give the skuas a wide berth to avoid being attacked in mid-air.
Meanwhile, some skuas in Iceland began to steal fulmar eggs in 1940, despite the ability of those birds to spit noxious oil at their enemies. The oil-dodging behaviour spread through the skua population and, today, it can be seen across the country.
The skuas of St Kilda
have another trick: night feeding. This remote archipelago hosts one of the world’s largest colonies of Leach’s storm petrels – small seabirds that only visit their breeding colonies in the dark. The skuas have somehow learned to catch them, and the knack has been passed on.
Another instance of dietary refinement in great skuas is the phenomenon of ‘rogue’ predators – individuals that have specialised in a niche food item, or in using an ingenious feeding technique.
Take the case of the skua that, knowing it would be relentlessly mobbed by a colony of Arctic terns if it dared to intrude into their airspace, took to approaching on foot instead, causing far less commotion as it did so and carrying off tern chicks at will.
One particular bird was well known for killing black guillemots by falling on them as they emerged from their burrows in the manner of a kestrel catching a vole. Other great skuas have, unfortunately, taken to attacking ewes and lambs, while a few, disturbingly, are apt to prey on the eggs and chicks of their own kind.
It isn’t adorable behaviour, but it does show remarkable adaptability.
A tender side
I have suggested that great skuas are more complex than people tend to believe, but is it a step too far to look for gentle qualities in the species? I don’t think so.
They do, for example, make attentive mates: the male and female form a strong, lifelong bond and demonstrate a tender togetherness. The birds meet up on their breeding grounds each spring after spending the winter at sea, and perform graceful displays, including an aerial show in which they glide side by side and call to one another (okay, I’ll admit that their duets are a bit gruff).
Later, during the egg-laying period, the male brings gifts of food for his mate, who begs for them with chick-like pleading, which is also sweet in its way.
If great skuas are so nice, then why do they mug intruders, including humans, with such evident gusto? The answer is that this violence is an expression of care towards their offspring. It is difficult to appreciate this when you are ducking out of the way of a skua’s rapidly approaching claws, but the bird’s determination to protect its young from interference is really quite admirable.