Thank a lemming

Many of you in the south are enjoying great sightings of Snowy Owls (Bubo scandiacus) this winter.  Most provinces and most northern states have had sightings, and the irruption has extended as far south as Oklahoma (so far).  Everywhere on Facebook I see friends and acquaintance posting photos of Snowy Owls, and or status updates on how they’ve succeeded or failed in their search for reported birds.

Now as most everyone knows Snowy Owls are birds of the Arctic. They breed up here, and spend their winters (usually) in the lower reaches of the Arctic and near polynyas (year round ice free waters) such as the North Water Polynya between Ellesmere Island and Groenland. I’ll not touch on the fact that despite their breeding in the neighbourhood (a friend saw 17 nesting pairs in a valley near here) I’ve only ever seen them in the south on one of their irruptions. They are a bit of a nemesis bird for me, but only because I’m somewhat lazy. I could end my northern Snowy Owl drought with a bit of effort and a trip farther inland by ATV.

But the fact is that most people who have seen them have seen them in the south on one of their irruptions, mass exoduses of their Arctic Home, which happen on fairly regular occasions of varying intensities. Why is that?

Well, if you have been lucky enough to see a Snowy Owl down south, you should probably thank one of these guys, a lemming. Lemming populations famously wax and wane, and with them go the fortunes of Snowy Owls, and a number of other Arctic predators.

Where I live, there are two species of lemmings, the Brown Lemming (Lemmus trimucronatus)  and the Collared Lemming (Dicrostonyx groenlandicus). The Collared Lemming is unique amongst rodents in that it changes colour in the winter to white. In Inuktitut they are known as Avinga, which is also one of my son’s names.

Lemmings are active all winter under the insulating snow, and soon after the Sun returns and begins to gain a little strength, you start to see their tracks in the snow as they wander about. I’ve long wanted to photograph one on one of these over snow journeys, but on the few occasions I’ve actually seen them up on top of the snow they’ve proved very difficult to capture. Lemmings simply do not hold still for a shot and move constantly away from you, resulting in my having a lot of blurry photos of lemming butts. Their bolting away shouldn’t be a surprise given their position on the food chain, just above grass and seeds.

Lemmings are the linchpin of terrestrial food chains up here. They are on the diet of every Arctic predator outside the ocean. Peregrine don’t take many, being more of a bird prey specialist, but apart from that they are the daily feature on the menu of foxes, ermine, wolves, Rough-legged Hawks, Gyrfalcon and especially Snow Owls.

Lemmings have cyclical populations that build from low numbers into years where the populations explode, only to crash and then start the cycle over again. Lemmings can have four or five litters a year of as many eight young. They are able to breed at the age of 5-6 weeks so it is easy to see, given the right conditions how quickly their population can grow. And when lemmings have a good year, predators such as Arctic Fox, Ermine and Snowy Owls adjust their breeding to take advantage of the bounty. Arctic Foxes will have as many as 16 kits on good lemming years. A friend of mine saw a family of eight Ermine while hiking this past summer.

Snowy Owls produce large broods of up to 14 chicks on years when lemmings are plentiful. A brood of nine chicks will be fed something in the order of 1500 lemmings from the time they are hatched until they are independent.  Remember that friend of mine that saw 17 breeding pairs of Snowy Owls in a single valley? If they each raised nine owlets, the owlets alone would have eaten over 25,000 lemmings from that valley.

So this was a good summer for lemmings, a very good year. They were everywhere, including a couple of them that inhabited a cage in my house for a while (they were released back where they were caught). They actually make very good pets, becoming very tame quite quickly. And because it was a good year for lemmings it was a very good year for Snowy Owls, who produced large broods.  As these broods have grown into juvenile birds there is more and more competition for fewer lemmings and they begin to disperse farther and farther afield, resulting in the irruption that many of you are enjoying now. I think that you’ll find that most of the Snowy Owls you are seeing are juveniles.

And they are probably having a hard time down there without an abundance of lemmings to sustain them. So please remember that when you are trying to get a better look at one, or get that once in a lifetime photo shot. The energy they expend will be sorely needed to get them through the winter and get them home to their breeding range up here. And when you do see one, remember to give thanks to the lowly lemming that is the reason you are seeing those magnificent birds in your backyards.