Winter is Here

Hi folks! Apologies for the slight delay in getting this out. I have been recovering from a recent bout of COVID-19. Since the pandemic started, I’d actually managed to avoid getting the virus, but it finally got me last week.

There has been much talk about the colder weather recently, and it has definitely created a more festive and atmospheric scene across the reserve. It doesn’t take much for the lochs to start freezing over, because they are relatively shallow, and a thin blanket of snow beautifully transforms the surrounding pine forest and hills. But how do birds cope with the colder temperatures? If you go for a walk in the local woods, you’ll notice that instead of being evenly spread throughout the area, several species group together in fairly loose and large feeding flocks. Flocking together in winter increases their chances of locating food. Overnight, birds will huddle together to help conserve body heat. The principle of ‘safety in numbers’ is especially critical in winter, when birds are conserving energy and more eyes also means a better chance of spotting and therefore evading a predator, such as a Sparrowhawk. Flocking becomes especially important for birds during the late afternoon and evenings, when many species will develop massive flocks, both to keep warm and lower the risk of being picked off as dinner, for a predator! This is why species like Jackdaws and Rooks will gather in their hundreds in farmland woods.

At the moment I find myself easily spotting in excess of 20 birds on the feeders next to the office, species such as Coal Tits (the most numerous on our feeders) Blue Tits, Great Tits, Robins and Chaffinches, eagerly packing in the calories throughout the day. Long-tailed Tits, Treecreepers and Wrens also regularly congregate in large numbers like this to feed and conserve heat. Smaller birds especially, have to feed at an accelerated rate, while also ensuring a proportion of their time is spent keeping warm and conserving energy. It’s an extremely fine balancing act and one that unfortunately, can go wrong. The smallest birds have to feed during most of the daylight hours and consume a hefty quantity of food, up to 30% of their body weight on a daily basis! This ensures they can maintain those fat reserves, which is a difference between life and death during the coldest of winter nights. So, if you’re planning to put out feeders yourself, then you really will be helping them out. Hoarders such as Red Squirrels and Jays have already done much of their hard work. In tougher times, they can resort to their larders, which they prepared back in the autumn when food was more abundant.

The biggest challenge for wild birds in winter is to find food sufficient enough to accumulate fat reserves to store on the body and burn for energy. This becomes extremely difficult in cold weather when snow and ice hide once easily found food supplies. We have many species of wintering waterbirds here, such as Goldeneye, Goosander, Wigeon, Teal, Whooper Swan, Cormorant, and more numerous species including Grey Heron and Moorhen. If the temperatures really take a tumble for a sustained period, such species may be forced to leave the lochs in preference for coastal wetlands. But this really would require a substantial big freeze. Will that happen this winter? We’ll have to wait and see.

Snow camouflage is a fascinating transformation seen in a range of species during the winter months, when fur or plumage turn white in response to climate. Scotland is home to two mammal species which do this, the Stoat and Mountain Hare, and one bird, the Ptarmigan. Stoats live here on the reserve and the surrounding areas, and I have been fortunate enough to spot them a few times. Although Mountain Hare might not live specifically on the reserve, they do live in the surrounding higher hills, the nearest population probably being on Morven, an 871-meter-high Corbett, just by the reserve. I thought this winter edition of our blog would be the perfect opportunity to talk a bit about these unique species in a bit more detail.

Nimble, elusive, and very competent climbers, stoats will happily take on larger animals, with Rabbits being their preferred prey. They usually have a light brown coat, white belly, and a black-tipped tail, for most of the year. But in winter, depending on which part of the UK they inhabit, they will turn a patchy brown and white combination, or completely white where the climate is colder. For example, in most of inland Deeside and northern Scotland, Stoats turn white in November most years. This is in anticipation for snow and frost, if they can blend into their surroundings, they can hunt prey more successfully. This colour morph or plumage is known as ermine, a genetic trait passed down the generations. In southern Scotland, away from the increased chance of snow, only about 30% of stoats change colour, and in England and Wales, few stoats ever change colour. But interestingly, it has been recorded before some severe winters have occurred (a recent example being 2009-2010), that Stoats turned white even south of the border. The process of changing to white is quite complicated, but put simply, decreasing daylight hours and lowering temperatures, stimulate receptors in the eyes and skin to send information to the brain, activating the production of a white moult with extra dense fur.

Mountain Hares are Scotland’s and the UK’s only native hare and an important species for indicating a healthy ecosystem in Scotland’s hills. They also turn white in winter thanks to the same process that causes Stoats to change colour. This camouflages them in the snow and helps hares avoid predators, especially birds of prey like Golden Eagles. They are now classed as ‘Near Threatened’ in Scotland on the UK Red List of Mammal Species and subsequently, have been given full protection in Scotland from March 2021.

Historically, they have thrived in managed grouse moors, but in recent decades, they have undergone excessive persecution from Game Keepers, because it has been thought that they are a significant harbourer of ticks (despite considerably more numerous sheep and deer occupying the same habitats and presenting far larger hosts for ticks!). Ticks can cause deaths in Red Grouse chick populations. It is estimated that up to 25,000 hares were being culled each year, which, according to some sources, was approximately 10% of the Scottish population! But since Monday 1st March 2021, Mountain Hare have been included on Schedule 5 of the Wildlife & Countryside Act 1981, which has given them full protection, meaning that culling can only happen in a closed season, under license.

Mountain Hare and Ptarmigan are among the only true Arctic species naturally found in Scotland and are sometimes referred to as being an ‘Ice Age Relict’ species. An Ice Age relict or ‘Glacial Relict’ is a population of a cold-adapted species that has been left behind, as their geographic range has changed after an ice age ends (from glacial maximum to glacial minimum or interglacial). This happened about 10,000 years ago, when Mountain Hare and Ptarmigan were left behind in the UK, as the North Sea land bridge known as Doggerland flooded and became sea. Glacial relicts are typically found in enclaves under relatively benign conditions. In the case of Mountain Hare and Ptarmigan, the Scottish Highlands is an example of such an enclave, an island of Ice Age habitat in effect, surrounded by an otherwise warm and temperate sea of ecosystems further downhill.

Ptarmigan are Scotland’s hardiest birds and also live on Morven and the higher hills surrounding the reserve. In Scottish Gaelic, their name ‘tàrmachan’, literally means ‘the croaker’. Very fitting. If you’ve ever accidentally flushed one and heard its call, you’ll know exactly why they were given that name. There are many place names in the Highlands such as Tàrmachan Ridge (near Ben Lawers), which refer to these birds. They’re accustomed to the Arctic Tundra, the High Arctic, Iceland, the Alps, the Scandinavian Peninsula Mountain chain, the Ural Mountains, Siberia, Canada, and Alaska. So, for ptarmigan living in Scotland, it must be relatively balmy here, when compared to these considerably harsher environments!

The highest Highland mountains are the only place in the UK, which remotely resemble their true habitat, and sadly climate change is definitely a threat to this species in Scotland. A place which is already on the very western edge of its Arctic Alpine range. In fact, they have declined by 81% here since 1961. Mountain hare and Ptarmigan are beautiful creatures, part of Scotland’s unique natural heritage and symbols of healthy biodiversity, it would be so sad to lose them. Let’s hope they can both return to stable thriving populations.

Female Ptarmigan conserving energy.

That’s all for this week. Take care, wishing you all a very Merry Christmas and Happy New Year from me, Kirsten and all the team at Dinnet! Thanks for reading. Danny.

About dannyfabianharvey

Danny works for NatureScot as an Assistant Reserve Officer, at the Muir of Dinnet National Nature Reserve, in the Eastern Cairngorms National Park. He graduated in 2019 with an MSc in Ecology and Conservation from the University of Aberdeen. This has provided him with the scientific rigor required when dealing with issues of Ecology and Conservation, coupled with a profound respect for wildlife and habitats. He directs his own short films, two of which were Highly Commended in the British Wildlife Photography Awards 2018. Currently, he is co-directing and filming a documentary feature called, 'The Bough Beaks', with independent production company, Mousehole Films, due to complete in the summer of 2023. Danny is regularly booked for his lively talks on Wildlife Filming, where he discusses the joys, challenges and techniques. Recently he has started working as a freelance bird surveyor, having conducted multiple farmland bird surveys for the James Hutton Institute for their Framework program. Previously, he has worked with the RSPB, Trees for Life and Aquila Ecology.
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