Satellite tagging is an important tool of modern conservation science and it is leading to a whole new understanding of sea eagle behaviour in Scotland and around the world. You can find out more about satellite tagging from RSPB Scotland’s head of species and land management here. The particular devices we use weigh 90 grams, or between 1.2 and 1.8% of the birds’ weight. They’re solar powered and fitted with a Teflon harness which is designed to last around 5 to 7 years, after which the hemp thread holding the Teflon together breaks and the tag falls off. This gives us the birds’ exact location anywhere from twice a day in the winter to every hour in the spring, throughout its early years and a short way into adulthood.
Currently we’re learning a great deal about how they disperse in their first year, how they explore the landscape and ultimately which areas are most important to them. Key roost sites and feeding areas are becoming evident as more tagged birds take to the air. With a bit of luck and a lot of patience, eventually we will be able to see how these early experiences lead them to settle in a territory of their own, with a partner they may have met many years before. None of this would be possible with standard fieldwork practices because of the distances involved and the difficulty in identifying individual birds.
There are now 7 sea eagles that fledged from nests in East Scotland carrying GPS satellite transmitters. Four of these hatched just 7 months ago and already most have left their parents protection and ventured out to explore their new home. We’ll look at the dispersal of this year’s chicks in a future blog once they have all moved away from the nest area, so in this blog we look at how the oldest 3 have fared over the last year.
October 2016 to January 2017. White K is in orange, White Diamond is in green and White L is in blue. This shows the first few months of the younger birds’ dispersal and White K’s expedition out to Mull.
White Diamond, Strathspey 2016
White Diamond is a female that fledged from the nest in Strathspey in 2016. Her only contemporary was White L, a male from the nest in Fife. She has been the more adventurous of the two, having covered 6000km in 12 months, compared to White L’s 5000km. During the last 12 months she’s been in every direction, using distinctive ‘loops’ to explore, which contrast strongly with White K’s straight line ‘there and back’ expeditions.
One of her early expeditions took her right out into the farmland of Aberdeenshire and almost to Fraserburgh in the north east corner of the country. Others took her south to Loch Rannoch and west to the fringes of the west coast population where she undoubtedly met other sea eagles. But much like White K she returned to the familiar mountains of East Scotland. Shortly before the Rannoch expedition, which eventually took her within sight of the Isle of Skye, she was in the company of White L in the Angus Glens. White L followed her as far as Loch Rannoch, staying a respectful 7km behind her, but they roosted separately and he flew back the next day.
In April she settled in the Monodhliath mountains, where she has now spent the majority of her time using the rivers and burns to hunt and scavenge. From observations at the roost sites there are plenty of other young sea eagles around, aside from White K probably all west coast in origin. Unlike White K she uses the whole of the mountain range, including the occasional trip over Loch Ness, rarely visiting the same area as the day before.
February to April 2017, showing White Diamonds looping expeditions and White K’s return from Mull
White K, Angus Glens 2015
White K, a male, is the oldest satellite tagged sea eagle from East Scotland. It has now been 2 years and 7 months since he hatched on a nest in the Angus Glens. At the end of 2016 he had travelled all the way out to the isle of Mull on the west coast, where he must have met many other sea eagles. Much to our relief, he headed east again in April and settled in the Monadhliaths. Sea eagles are very sociable and these birds are no exception. White K first met the 2016 female chick from a nest in Strathspey, White Diamond (see below), shortly after she had dispersed into the Cairngorm mountains, where they spent several weeks hunting and roosting together on and off.
May to July 2017. A relatively sedentary time of year of year with White K, the oldest, not travelling more than 20 kilometres from his favoured roost.
Over the last few months they have both been using the Monadhliath mountains, but remaining largely separate and using different the landscape quite differently. It remains to be seen whether this is the quirks of individual behaviour or a pattern associated with their sex. Aside from a short foray into Deeside In October he has remained in this area and has recently been seen hunting over Insh Marshes.
White K in the Monadhliath mountains, September 2017
White L, Fife 2016
White L, a male, fledged from a nest in a Forestry Enterprise Scotland woodland in Fife in August 2016. After spending a few months being fed by his parents, Turquoise 1 (female) and Turquoise Z (male) and building up his courage he left the safety of their protection and ventured off on his own. In previous years young sea eagles from this territory have stayed until February, most likely because there are no other young eagles close by to draw them away, but White L seemed particularly tenacious and left right on time – most fledgling sea eagles will disperse in September or October.
He first headed north through the lowlands of Angus and Aberdeenshire, reaching Inverurie before turning around and heading all the way back to Angus. After a few more weeks in the Angus farmland full of brown hares, rabbits and pheasants, he then headed up into the Angus Glens, probably having spotted another eagle to go and investigate. It wasn’t long before he’d bumped into White Diamond (see above), a female just a few weeks older, and they roosted together in Glen Tanar forest on a few nights.
August to October 2017, showing White L’s exploration of Perthshire and Stirling.
Since then he’s continued to explore the uplands of East Scotland, coming within a few miles of Inverness in the north and Loch Ericht in the west. More recently he has headed south west and explored Pertshire and Stirling, eventually reaching Loch Katrine in the Trossachs, before returning to the Angus Glens.
An interesting read, especially White L. I happened to be at Loch Katrine on July 6th and was advised to keep my eyes open for the eagle as the steam ship I was on headed across the loch. No such luck, though I was delighted to see two stunning ospreys instead. I hope these magnificent birds (and the ospreys!) continue to do well.