Suilven, an Assynt Golden Eagle

January 21st 2016

Many of you will remember me writing about “Suilven” the young golden eagle that hatched in Assynt in April 2010 and was fitted with a satellite tag by Roy Dennis. He was named Suilven by the children of Lochinver and Stoer Primary Schools at the time. Well I wanted to write and update you with what Suilven has been up to in his first five years of life. You will be glad to know that he is doing well and after roaming the Highlands of Scotland has returned to Assynt and is looking for a place to set up home.

He was ringed by Doug Mainland, Roy Dennis and myself in June 2010 from a nest on Glencanisp estate. His female sibling was collected under SNH licence by Lorcan O’Toole for the Irish golden eagle reintroduction project in County Donegal. It is fairly rare for eagles to have siblings and the reintroduction programme in Ireland was only allowed to take a single chick from nests that had two young. Suilven, the remaining youngster was ringed and fitted with a satellite tag and then returned to the nest.

Suilven being satellite tagged
Suilven being satellite tagged

He has obviously done well and the satellite tag has allowed Roy and his Highland Foundation for Wildlife to monitor Suilven’s movements ever since.

The reason for the satellite tag is to allow scientists and conservationists to gather data on what happens to young eagles when they leave the nest. The tags do not disrupt the bird’s activities and are designed to naturally fall off the bird after about five years.

This is what we found out: After fledging Suilven remained close to the nest throughout July and early August of his first year before starting to range more widely towards the end of August. He explored Canisp and Glendhu and then returned to his parents’ home range and spent the rest of the year there. There were plenty of rabbits afflicted by myxamatosis, which must have provided easy hunting opportunities for a young eagle.

In January 2011 he headed to the Fannich Hills and then ranged very widely throughout the spring and summer of his second year, including a visit to Skye. In 2012, he ranged north to Durness but spent much of the summer in mid Sutherland between Glencassley and Strathvaich. He seems to have spent the winter near to Loch Glascarnoch so perhaps some of you saw him on a trip to Inverness.

In 2013, Suilven ranged from Assynt north to Kylesku and to Loch Eriboll in February. He spent a lot of time near Elphin, Ardgay and the Lairg area. But by October 2013 he was returning more and more to Loch Assynt and the Lochinver area.

click to enlarge
click to enlarge

This map shows the range of Suilven in 2014. Many thanks to Roy Dennis and the Highland Foundation for Wildlife for allowing us to use it.

In November 2014 he moved to the moors south of Altnacealgach however, the batteries on the satellite tag started to fail and the transmission became intermittent and then stopped altogether.

Suddenly in mid-August 2015 Suilven’s transmitter started to give signals again near Loch Borralan, Ledmore. On closer inspection of the data it seems likely that the satellite tag had dropped off and the sunshine during August had boosted the solar panel allowing the transmitter to burst into life.

Despite looking Roy cannot find the tag but he is certain the transmitter came off Suilven last November after 4.5 years of study – this is what these transmitters are designed to do when they reach the end of useful data gathering. It would appear that Suilven was trying to find a place to breed in his natal area. We wish him good fortune and he has taught us a lot about immature and sub-adult golden eagle behaviour in the NW Highlands.

For more information on Suilven and other eagle monitoring go to http://www.roydennis.org/animals/raptors/golden-eagle/

Andy Summers
Senior Highland Council Ranger for Caithness and Sutherland

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