Snowy Owl

Allow me to take you north and east, out of the Western Palearctic to the Lena delta in arctic Siberia. It is June and the sun will not dip below the horizon until early August. Spring is late this year, and temperatures have been below zero for much of the month. Nevertheless, there is plenty for me to record while waiting for the ice to break. Flock after flock of Curlew Sandpipers Calidris ferruginea and other waders have been arriving, often in full song, only to huddle together on the gravel banks of a small stream of melt water that has cleared away a little snow. 

The wind has been strong most days, and very cold. On a day of mild southerlies, the snow melts. When the wind stops altogether, every creature makes the most of a few precious hours of calm. Pacific Golden Plovers Pluvialis fulva whistle, Pectoral Sandpipers C melanotos boom and Red-throated Pipits Anthus cervinus sing over new claimed territories. Soon a fresh gale starts from some other direction. Blizzards blanket the tundra and all the waders flock to the gravel again. 

We are staying at the Lena-Nordenskjöld International Biological Station, situated on the banks of the main channel of the Lena, about 65 km from the nearest town of Tiksi. Its scientific director is Dr Vladimir Pozdnyakov. I have maybe 200 words of Russian while Vladimir and colleague Yuri Sofronov speak about the same amount of English. We are able to talk about a few things, but there is so much more that I would like to ask. 

There is no spring here, only a monumental battle as summer wrests power from winter. In front of the station lies an 8 km wide stretch of the river Lena. When I arrived it was covered in a thick layer of ice. At the river’s source some 4400 km to the south, winter ended weeks earlier. Here in the delta the ice rose slightly higher each day on the accumulating melt water, cracking here and there until it almost reached the top of the riverbank. Eventually we saw some clear water somewhere far out in the middle of the ice. The break-up was rapid, and on 16 June we awoke to find that the last ice sheet near the station had finally gone.

After several weeks in a tundra landscape of rolling hills, we are navigating a labyrinth of channels between tiny, flat, waterlogged islands. Woolly Mammoth Mammuthus primigenius bones still emerge from the banks each year. It is strange to see Willow Grouse Lagopus lagopus flying low over the water like ducks. On making a short stop, we hear the ecstatic long calls of a pair of Ross’s Gulls Rhodostethia rosea. They are heading for the outer delta, and so are we.

As we make our way towards the island of Nizhny Bobrowski, the big question is whether this will prove to be a ‘lemming year’. The four-year lemming cycle suggests it should be, but proof is lacking. Most years, lemming numbers are low and there are no Snowy Owls Bubo scandiacus at all in the delta. We did not see many lemmings at the station, but a single male Snowy hunting on its slopes gave me some hope. Vladimir tells me that conditions in the delta itself can be very different. Navigating one channel, I think I see a distant Snowy on the ground. Vladimir is not convinced. Then after flushing a female from the top of a bank, right beside the channel, we jump ashore to investigate. 

Snowy Owls do not nest on snow. They prefer windswept places where the snow clears first. The nest of this pair is on a flat area near the highest point of a steep bank. It contains six eggs as well as several dead Siberian Brown Lemmings Lemmus sibiricus. I am impressed to find the severed head of a Stoat Mustela erminea nearby, among moulted feathers and pellets. While Vladimir and Yuri take measurements for a paper they are working on (Pozdnyakov & Sofronov 2005), I make my first Snowy Owl recordings. At first the male mobs me with furious cackles. Soon he settles on the opposite bank where he fixes me with bright yellow eyes, lowering his wings and holding his body in a horizontal position. He inflates his throat, then hoots while thrusting his head down and cocking his tail at right angles to the ground (CD3-47). 

Less then 3 km further along the same channel we find a second pair, this time with five nestlings and three eggs. One of them is still hatching, a task that may take up to three days to complete (Potapov & Sale 2012). The second male does not mob us but starts hooting from the opposite bank almost as soon as we arrive near the nest. The female stays further away. Like all that I recorded, the male in CD3-48 hoots in two-note ‘strophes’, the first hoot marginally higher than the second. At other times, they may give single-note hoots. There is no running water in the recording, because I am using a parabolic microphone and have positioned it low, where it has a ‘view’ of the owl but not the channel. Instead, we can hear at least nine other species of tundra birds. 

Besides hooting in threat to enemies like us, male Snowy Owls hoot to other males as a territorial display, and to females to gain their attention. In the Lena delta in 2004, nests were no closer than 1.5 km from one another (Pozdnyakov & Sofronov 2005) so presumably males can hear each other from at least that distance. Human observers have reported hearing hoots at distances from about 1 km (Potapov & Sale 2012), to an incredible 11.3 km (Sutton 1932). 

When do Snowy Owls hoot? The extreme difficulties involved in Arctic fieldwork in late winter mean that the beginning is difficult to establish. Schaanning (1907) heard ‘courtship notes’ in Novaya Zemlya as early as 5 April, and Sutton (1932) heard hooting on Southampton Island from 25 April onwards. Hooting is frequent during incubation and the early nestling phase, based on my own experience. Watson (1957) heard it frequently on Baffin Island until the end of July, with the last male hooting on 23 August, after its young could fly. 

While the male Snowy Owl’s hooting dominates the spring soundscape, the female hoots rarely and then only close to the nest (Potapov & Sale 2012). I have never been lucky enough to hear female hooting myself, but Scherzinger (1974b), who worked with captive birds, wrote a detailed description. A recording by Claude Chappuis of a captive individual seemed to fit the description (Deroussen & Millancourt 2003). I sent it to Scherzinger and he agreed it was a female. The rhythm and posture are essentially the same as in the male, but the timbre is quite different. Each high-pitched hoot of the female combines a hoarse descending squeak and a sound like a cough or a bark. Being higher-pitched and hoarse, her hoot does not travel very far. 

One of the female’s commonest calls during the breeding season is her soliciting call, a powerful, shrill and slightly hoarse whinny. As the male approaches, the female crouches and sways her head and the front part of her body, before meeting him with spread wings. In CD3-49, the female’s whinny appears at 0:03 and 0:12. The guttural clucking from the male at 0:02 after his first double hoot is a sound associated with food-offering, whether by male to female or young, or by female to young (Tulloch 1968). In this case I was standing near their nest, so the food exchange was probably false: a displacement activity. In such situations males often pass food or even clumps of turf to their mate, or else the pair may copulate (Watson 1957). 

Snowy Owl is one of those species whose formal description dates back to the founder of modern taxonomy, Carl Linnaeus. 

In fact “L.”, as he is often called, described two species, Strix scandiaca and S nyctea (1758), based on drawings by his teacher Olof Rudbeck of a male and female, respectively. Perhaps he also had some experience of them as winter visitors to the farmland around the city of Uppsala, Sweden. Strix was the genus in which Linnaeus placed all owls but as it happens, the Strix owls in the modern sense are among the Snowy Owl’s closer relatives (Wink et al 2009). In the course of a long and complicated taxonomic history, L’s two ‘Strix’ species were combined into Nyctea scandiaca, a name that remained stable for many years, until genetic studies rocked the boat.

Comparison of both mitochondrial and nuclear DNA has shown conclusively that Snowy Owl is in fact an Arctic species of eagle-owl Bubo. According to Wink et al (2008, 2009) and Omote et al (2013) its closest known relative is the Great Horned Owl
B virginianus of the Americas. Most criteria for defining a genus are quite woolly, but two are very clear. A genus should be a ‘monophyletic clade’, consisting of an ancestral species and all of its descendent species, and if new insights mean that two genera have to be merged, the older name has priority. That is why Bubo (1806) consumed Nyctea (1826) and went on to swallow up Ketupa (1830) and Scotopelia (1850).

The expanded and now monophyletic genus Bubo can be divided into three further clades, each of which branched off at a different point in time. The oldest clade includes the fish owls, formerly Ketupa, the fishing owls of Africa, formerly Scotopelia, and at least four eagle-owls from Africa and Asia. The next to evolve was the Snowy Owl and Great Horned Owl clade. The most recent clade includes all the other eagle-owls mentioned so far in this book – Spotted B africanus, Indian
B bengalensis, Pharaoh B ascalaphus, Cape B capensis, Eurasian B bubo and presumably also Greyish B cinerascens and Arabian Eagle-Owl B milesi. The mewing whinny of the female Snowy fits well with this phylogenetic tree. Soliciting calls in both of the older clades are relatively high-pitched mewing or whinnying sounds. Soliciting calls in the most recent clade are very different: Eurasian and its closest relatives beg with harsh sounds that use a wide range of frequencies. 

Adult Snowy Owls also use a mewing whinny or whistle in distraction displays, and in the latter part of the breeding season this is the whistle a human intruder is most likely to hear. Watson (1957) saw many distraction displays, which involved trailing and threshing the wings, spreading the tail and swaying the head from side to side. It was usually the female that whistled during distraction displays, but Watson once heard a male giving a similar call in the same situation. 

I never saw any distraction displays in arctic Siberia, although the owls did subject me to other defensive measures. Being dive-bombed by a huge white owl is something I shall not easily forget. It happened that very first time when we jumped out of the boat, as soon as the male found me alone. During the bombardment he used his ‘devil’s cackling’ call (CD3-50).

As in Eurasian Eagle-Owl, devil’s cackling is an expression of general excitement and not just an alarm call. Snowy Owls cackle in sexual excitement, when attracting a partner to the nest and in response to rivals. In many situations they hold their body horizontally, with the head low, then jerk the tail upwards with each cackle (Scherzinger 1974b). When alarmed, however, they cackle in an upright posture as shown by Håkan’s illustration.

Female devil’s cackling is easy to tell from that of the male, being distinctly higher-pitched with a squeaky quality. In CD3-51, a female cackles at close range. In the long gap between the first and second cackles, the nestlings chitter faintly, eg, at 0:34. At 1:27 the male interrupts his hooting to cackle too. 

When Vladimir and Yuri had finished taking measurements at the nest, I moved in to make a quick recording of the young, the oldest of which was c 10 days old. In CD3-52, you can hear two loud series of chitter calls, a sign that the young were cold or stressed. I would have liked to record more of their calls but clearly it was time for me to leave.

When the young leave the nest their bodies and heads are covered with their second downy plumage known as mesoptile. Their wings soon grow white, dark-barred ordinary feathers, which are concealed in the grey mesoptile at rest. A juvenile lying down on the tundra looks like a grey boulder, but when a parent flies in with a lemming, suddenly the boulder stands up and waves white wings. The earliest form of begging call – a short psu or psju – gradually becomes longer, more whistling and louder as the nestlings grow. By the time they are fully-grown, their begging calls sound quite like soliciting calls of adult females. CD3-53 has the falling pitch typical of owls one month or older (Scherzinger 1974b). Juveniles beg until they are three to four months old. By the time they can fly, their begging calls may be heard from over 1.6 km away (Tulloch 1968). 

Snowy Owls are among only a handful of bird species that are capable of wintering in the Arctic. Two of the others, Rock Ptarmigan Lagopus mutus and Willow Grouse L lagopus, are their most important winter prey when lemmings are not available. Alternatively, some Snowy prey on sea ducks wintering in polynyas in the polar ice (Robertson & Gilchrist 2003). When the midwinter skies are clear, the owls hunt by the stars and the northern lights: there is no daylight at all.

Snowy Owls that winter on grasslands south of the taiga zone thrive on a more varied and plentiful diet of small mammals and birds. Still, it is not exactly the Serengeti. When Mark and Mo crossed southern Canada three decades ago, the temperature was so low and the railway was so straight that the train would freeze into a straight line. When it finally had to turn a corner, men would get out and knock ice off the vestibules with hammers. It was not easy to spot the Snowy Owls they dreamed of seeing, sitting in such a white landscape. The one they did eventually see was flying alongside the train. 

When food is plentiful and disturbance is limited, it is sometimes possible to find concentrations of Snowy Owls. Logan Airport near Boston, Massachusetts, USA, has had up to 23 individuals present at one time (Smith et al 2012). Grain terminals in the Duluth-Superior harbour area (Minnesota/Wisconsin) are another ‘hotspot’, thanks to plentiful Brown Rats Rattus norvegicus. Evans (1980) studied territorial interactions between Snowy Owls wintering there, and found that they could be surprisingly vocal. The owls, mostly females, defended their winter territories with “high pitched, drawn out screams”.

In the Western Palearctic, Snowy Owls are relatively rare. Håkan has probably seen more wintering in Sweden than anybody else alive, but never more than five together at the same place, and those were always silent. In North America, five is ‘peanuts’. In early December 2013, an unprecedented influx of Snowy took place in Atlantic Canada, the north-eastern USA and the Great Lakes region. Nowhere was this more apparent than in Newfoundland. In one weekend, Bruce Mactavish saw 301 Snowy in the south-eastern corner of the island. While this was thrilling for a birder, the owls were close to starvation. Bruce found a dead one, and it was very thin. Owls were flying high and out to sea while others were coming in off the sea. They were pretty tolerant of one another, although they did tend to spread out over a large barren area. With nothing to fight over, none of them were calling.

Migrating Snowy Owls may occur in large concentrations more often than we think, although usually we only see one at a time. Potapov & Sale (2012) developed a fascinating theory after they noticed that as soon as the first Snowy appeared on their study site in the Lower Kolyma in spring, there would always be more at some distance. They believe that almost the entire population of Snowy can be divided into about five to 10 ‘loose boids’, huge but widely dispersed aggregations that move through vast areas of the tundra in spring in the hope of hitting good lemming areas, if any exist that year. The individual owls keep their distance but influence each other’s movements, so that a boid may occupy hundreds of km of tundra. Each one is capable of producing 300 to 2000 breeding pairs. Potapov & Sale (2012) believe that one such boid roams across northern Europe, from Scandinavia and Novaya Zemlya to the Taimyr peninsula, an idea that is at least loosely supported by satellite telemetry (Solheim et al 2008, 2009).

Europe’s Snowy Owls have not always been confined to the Arctic. For much of the last million years they occurred widely in southern and western Europe, with records as far south as Gibraltar (Eastham 1968). Their oldest known remains come from Early Pleistocene France, and we know that they bred there in the Middle Pleistocene thanks to immature bones found in Bouches-du-Rhône (Mourer-Chauviré 1975). Much more recently, the Magdalenians of south-western France were obsessed with Snowy. At several sites associated with these sophisticated hunter-gatherers, archaeologists have found unusual numbers of their remains. (In recent times, Inuit have also hunted Snowy Owls, and the Inuit name for Barrow means ‘the place where we hunt Snowy Owls’.) Cave art in Trois Frères shows a pair at a ground nest, although Short-eared Owl Asio flammeus is difficult to rule out (Eastham 2012, Potapov & Sale 2012). Another more safely identifiable image comes from La Portel cave, and has been dated to 11600 BP (Clottes 2002). 

Ice Age remains from North America are much scarcer and mostly Late Pleistocene, leading Potapov & Sale (2012) to suggest that Snowy Owls arrived there after expanding their range from Europe. A different line of thinking leads me to the opposite conclusion. Snowy only breed when there are wsufficiently high concentrations of lemmings, and they prefer collared lemmings of the genus Dicrostonyx (Dorogov 1987). The form ancestral to this genus, Praedicrostonyx hopkinsi, appears in the earliest Pleistocene glacial period in North America, but only later in Asia (Yalden 1999). According to the molecular clock, the ancestral eagle-owl that gave rise to both Snowy and Great Horned Owl lived around 4 million years ago (Wink et al 2009). There is a gap of around 3 million years until the earliest appearance of Snowy in the fossil record. During the intervening period, I envisage a ground-dwelling eagle-owl on the North American prairies that coevolved with its favourite prey and only became white during the course of the Pleistocene, when collared lemmings adapted to live in Arctic conditions.

In the southeast of our region, another very large owl can only survive when some of its habitat remains ice-free. Its range once stretched from the eastern Mediterranean to southern Asia. All that remains is a relict population that was only hypothetical until 2009. We were thrilled to take part in its rediscovery.