A fascinating new study has been published today in the peer-reviewed scientific journal Diversity, providing an in-depth analysis of the movements of young satellite-tagged golden eagles in Scotland and an examination of the physical barriers (water and unsuitable terrestrial habitat) that may restrict movement between different regions of Scotland.
Here’s the citation: Fielding, A.H. Anderson, D., Barlow, C., Benn, S., Reid, R., Tingay, R., Weston, E.D. and Whitfield, D.P. (2024). Golden Eagle Populations, Movements & Landscape Barriers. Diversity, 16(4), 195.
It is the latest in a long line of scientific papers produced by the Golden Eagle Satellite Tag Group (GESTG), a formal collaboration of scientists and researchers from several organisations that are involved with golden eagle research in Scotland who share tag data & other information for the purpose of furthering golden eagle research and conservation. I’ll try and blog about the other papers soon.
Using over 7 million dispersal records from satellite tags fitted to 152 golden eagle nestlings between 2007-2022, this research found that there were no movements by young golden eagles tagged in the Highlands to the southern uplands.
Similarly, there were no movements from eagles tagged in south Scotland to the Highlands, with the exception of one young eagle in 2015 which flew north to the Highlands in 2016 but was later probably illegally killed in the notorious Eastern Highlands in May 2016.
These results provide justification for the bolstering of the vulnerable south Scotland golden eagle population by translocating chicks and juveniles from further north. Natural recolonisation by golden eagles from the Highlands is quite clearly unlikely.
The study also demonstrates the reluctance of golden eagles to undertake large sea crossings, as evidenced by the already-known genetic isolation of the golden eagle sub-population in the Outer Hebrides. No satellite-tracked eagles tagged as nestlings moved between the Outer Hebrides and the Inner Hebrides or mainland Highlands, in either direction. Three tagged eagles from the Outer Hebrides made several possible but apparently aborted attempts to fly towards the mainland Highlands.
Flights across smaller water bodies were less problematic with frequent movement of golden eagles between the Inner Hebrides and the Highland mainland. However, eagle flights between Lewis/Harris and the Uists in the Outer Hebrides were surprisingly rare.
The paper concludes that the Scottish golden eagle population appears to be composed of three relatively isolated sub-populations. The largest is in the Inner Hebrides and in the mainland (Highlands) north of the Highland Boundary Fault; the second is the large Outer Hebridean sub-population; and the third, and much smaller and more vulnerable, is the southern Scotland sub-population. The authors suggest that recolonisation of golden eagles in northern England is likely to occur from terrestrial flights from south Scotland as opposed to flights over water into NW England.
This study, along with all the others the GESTG has produced, highlights the importance of satellite-tagging golden eagles in Scotland and puts to bed the ridiculous claims made by the grouse shooting industry that ‘tag data serve no purpose other than to try and entrap gamekeepers‘ and there’s no need to satellite tag golden eagles because ‘we know all we need to know‘.
Of course we don’t know all there is to know about golden eagles in Scotland – indeed the research undertaken by the GESTG is revealing just how little we previously understood and how much more there is to learn. What is more certain is understanding why the grouse shooting industry is so against any form of raptor tracking (see here, here, here, here and here). Indeed, it was the result of satellite-tracking golden eagles and uncovering patterns of widespread illegal persecution on some driven grouse moors that played a significant part in the Scottish Parliament’s decision last week to introduce a grouse moor licensing scheme to tackle ongoing illegal persecution.
Thanks to generous funding from Natural Research, the paper is available free of charge and can be read/downloaded here:
Raptor Persecution UK 
Wow, some of the conclusions were unexpected, by myself. Just shows how important satellite tags and research are to uk wildlife.
That is a very surprising result: something I would never have guessed.Speculation: Were ancient Golden Eagles around the UK 20,000 years ago, about the time sea levels were last low enough for the UK to form a single land mass with the continent?Was that, then, the last time they could spread to all parts of the UK? It would have been a very cold time (cold enough to drive humans out). How could they have survived?It is possible nobody knows.If Golden Eagles did not spread before sea levels rose, then might population pressures have eventually driven them to undertake this apparently reluctant migration?Or, Golden Eagles finally managed to populate all parts of the UK by the simple expedient of very low numbers of unusually curious/brave individuals managing to cross natural boundaries over long periods of time? A drip, drip, drip… effect?Great research:-)
oops! Apologies Keith. I didn’t mean to plagiarise your comment. I guess its pretty obvious I didn’t read the comments before I posted mine. 🙄
Still, great minds eh?
Very interesting, and among several ‘new’ questions that might arise, I wonder how the outer isles sub-population got there in the first place? Are they the decendants of a post glacial population spread across the landscape before the sea level rose enough to put them off and is there any genetic work that might shine a light on that?
But then apparently, we know all we need to know about golden eagles now!
If they think tagging is to trap gamekeepers, then surely that is a very good reason to keep them tagged.
I was going to make the very same comment. If gamekeepers are illegally killing golden eagles then an industry that claims to be opposed to persecution of raptors should welcome any technology that roots out the criminals that undermine their good reputation. The fact that they do not merely underlines the lack of good faith in those claims to abhor illegal persecution.
The paper referenced in the original post demonstrates that there are other very good reasons to continue with tagging but even if there weren’t its role in helping to reveal criminality is a good enough reason by itself.