Back in February, project volunteer Murray Baird picked up a mortality signal for a 2011 released male white-tailed eagle, Red T, whilst radio tracking. An intense team effort with a little expert help from RSPB’s investigations team lead to the discovery of his carcase buried under several inches of snow below a wind turbine.
Every white-tailed eagle carcase that is recovered is sent to the Scotland’s Rural College (SRUC) for an independent post mortem, and although in this instance the cause of death seemed obvious, a full post mortem including toxicology (to test for chemicals such as pesticides or poisons) was carried out to rule out the any foul play that might have occurred.
Only a few weeks ago, the final post mortem results confirmed that the likely cause of death was trauma due to collision with a turbine.
“Red T” was one of the most “interesting” personalities amongst the East Scotland released birds. Despite getting off to a bad start after his release, he found his feet and was one of the most frequently spotted white-tailed eagles in Tayside. People enjoyed seeing him in Methil hill shortly after his release, and then at Tentsmuir Forest for a while. He then regularly spent time on Carsebreck loch near Braco and Glen Lednock near Comrie, where I would often see him on my “days off”.
This is the first white-tailed eagle to be found that has been killed by a wind turbine in Scotland. For the East Scotland Sea Eagle project, this is one of 27 fatalities that have been recorded since the project began in 2007.
To put this into context, my colleague Richard Evans, Senior Conservation Policy Officer at RSPB's Scottish Headquarters, has presented some of his research into the threats that face white-tailed eagles in a modern landscape:
"The same week that news broke of the disappearance in Aberdeenshire of the first white-tailed (sea) eagle fledged in the wild in the east of Scotland for more than 150 years, RSPB Scotland received a post-mortem report on a 3-year-old eagle from the east of Scotland release programme that had been recovered a short time previously at a windfarm in the Ochils.
As is often the case with bird post-mortems, the findings were not conclusive, but in this case they pointed strongly to collision with one of the windfarm turbines as the most likely cause of death.
Collision is just one of many perils for birds inhabiting modern landscapes, increasingly scattered with man-made hazards, such as communication masts, glass buildings, cables, pylons, motor vehicles and trains – all very much in addition to wind turbines.
For sea eagles in many countries, this is part of the price of success, as populations have made enormous recoveries from nineteenth-century campaigns of persecution, and the more recent pesticide crash of the 1950s and 1960s.
For example, in Germany, sea eagle numbers have been increasing steadily by 6% or more annually. At the same time, lead-poisoning (from ammunition fragments in unrecovered hunting carcasses scavenged by eagles) has overtaken collision with trains as the largest single cause of death, although trauma of all types combined (including territorial fights), accounts for more admissions to veterinary clinics.
Over the last 10 years or so, collision with wind turbines has become much more common in Germany, as numbers of both turbines and eagles have increased. Nevertheless, more eagles die from lead poisoning and other types of collision with other human artefacts, particularly with trains. Moreover, numbers are increasing rapidly, and eagles fledged in Germany have contributed to the continuing natural recolonisation of Denmark and the Netherlands, as part of widespread recovery across Europe.
A similar tale of recovery from persecution and pesticides in spite of increasing absolute numbers of deaths from collision and environmental lead poisoning can be found in Sweden, and many other European countries.
Away from the Baltic, Norway was the country in continental Europe least affected by the pesticide crisis. This fortunate quirk of (bio)geography led to it providing donor stock for the reintroduction of white-tailed eagles to Scotland in the 1970s. In the last decade, as in Germany, collision with wind turbines has emerged as an issue for sea eagles in Norway, in particular at a large wind farm on the coastal island of Smøla. This has led locally not just to a highly-publicised eagle casualty rate, but also territory abandonment and poor breeding success in the wind farm area.
As in Germany, this is against a wider background of steadily increasing eagle numbers, largely as range long lost to past persecution is reoccupied. Smøla is now widely regarded to have been a very poor choice of site for a windfarm, as noted at the time by NOF, the Norwegian BirdLife partner. The potential for conflict remains, as many of the prime sites for wind energy development in Norway are found on flat coastal islands that, like Smøla, support very high densities of breeding sea eagles. At the same time, Smøla has become the location of cutting-edge research into windfarm impacts on eagles, as well as possible mitigation or offsetting measures.
As sea eagles reintroduced into Scotland and Ireland recolonise more widely, it does seem likely that some birds will succumb to pressures of living in modern human landscapes – just as they do in similar landscapes in other parts of Europe.
We already know that 8 of the sea eagles released in the east of Scotland since 2007 have collided with power-lines (or been electrocuted) and 6 with trains. The new probable wind turbine casualty can now be added to these figures.
Over the same period, there have been three confirmed and three probable sea eagle deaths in Scotland due to persecution. And since 1989, there have been 63 incidents of illegal poisoning, shooting, trapping or nest destruction affecting eagles in Scotland. This includes 12 confirmed incidents involving sea eagles and 51 golden eagles, 31 of which were confirmed to have been illegally poisoned. Golden eagles were also the target of a further 37 incidents of probable persecution.
The small number of birds from the east Scotland release actually confirmed to have been illegally killed will doubtless be a large underestimate, because the vast majority of wildlife crime goes unreported, and if carcasses are recovered at all they are often in such a poor state that the cause of death cannot be determined. By contrast, accidental deaths are much more likely to reported, and quickly enough for a post-mortem to be carried out. This means that a simple comparison of the numbers of different known causes of death is likely to be flawed.
But as in most other European countries, the overall population trend in Scotland is very strongly upwards, as sea eagles expand into vast areas of low-lying, long-lost range. Knowledge and experience from countries like Germany, Sweden and Norway provides an insight into the likely nature of future problems for white-tailed eagles to the west of the North Sea.
So far, it also offers significant reassurance that strong recovery can continue even in spite of new pressures, provided vigilance is maintained and other appropriate steps are also taken to improve conditions for eagles more widely.
For Scotland, this means continuing to ensure that new development proposals with a significant risk of collision mortality are modified, or not given consent at all, in order to minimise their actual impacts. Marking key sections of electricity grid infrastructure could offset or avoid future problems. A switch away to non-lead ammunition for all types of hunting would probably avoid in Scotland the impacts currently seen in Germany and Sweden.
But the single most important change to benefit eagles would be a lasting end to the illegal killing of birds of prey, which still poses the most direct and significant threat to the long-term re-establishment of the species across its former range."