Sea Eagle Project Officer Owen Selly tells the story of a fascinating discovery

In the spring of 2013, six years after the first release of sea eagles into the Fife countryside after more than 150 years of absence, a few of these magnificent birds started to build nests in East Scotland. A pair of 2009 release birds built their first nest in a Forest Enterprise Scotland woodland in Fife , whilst a 2008 release female and a west coast male built theirs on a grouse moor in the Angus glens.

Turquoise Z (right) and his partner of five years, Turquoise 1, near their nest in Fife in 2016. Image credit Richard Tough.

Their fortunes could not have been more different. The Fife pair went on to successfully raise their first chick and have continued to do so every year since. The Angus pair watched as their nest tree was cut down in an act of targeted vandalism. Shortly afterwards the male disappeared and has not been seen since.

The following year, the female, known as A9/90 after her colour leg ring, found a new three year old mate, Red P, and they built a new nest elsewhere in the Angus Glens. This time they were not disturbed, but the egg she laid was infertile, which is not uncommon in younger birds. In 2015 things were finally back on track and A9/90 raised two healthy chicks with the male Red P.

 In 2016 they were again seen on the nest early in the breeding season but something must have gone wrong – by mid-April it became apparent they were not going to breed. Sightings of sea eagles in the area were infrequent and individuals were never positively identified. At the time they were assumed be the same pair, A9/90 and Red P, however in hindsight A9/90 may have already been missing which would explain birds being present but no breeding attempt made.

I climbed up into the nest later in the season to see if they had attempted and failed early, but there was no evidence they had done the necessary preparation, such as making a soft lining in the nest with a shallow depression, known as a cup.

As the 2017 breeding season approached, I was not optimistic that they would return, but in February during a coordinated watch to help locate nesting pairs, two adult sea eagles were seen on the nest.

Staff and volunteers continued to monitor the area and sightings of two other birds nearby were passed off as just being nosey and had visited to see what was going on. We even posted on facebook about a visit by one of them – sea eagles are a social species and often seek out and investigate other eagles.

 The new birds were 2011 Red Z, a big female who had previously been seen in Argyll, and none other than Turquoise Z, the male from the Fife nest. He is easy to identify even from a distance as at some point in his early years he lost his right wing tag. It had been known for some time that he occasionally visited the Angus Glens to hunt, despite the distance from his own nest, so it was surprising but not astonishing to see him flying overhead as we watched the nest.

Turquoise Z when he was first seen near the Angus nest in February 2017.

Then, at the beginning of April I set off on my usual hike up to a vantage point overlooking the nest and I was delighted to find a sea eagle laying low amongst the branches, clearly incubating eggs. From my position it was impossible to read the wing tags in the harsh light but the female, A9/90, doesn’t have wing tags so I assumed it was the male, Red P. That day I hadn’t seen any other sea eagles, but I knew the other bird would be off hunting and would return to take their turn incubating the eggs.

With great care not to disturb them I worked my way closer to a new vantage point, 700 metres from the nest. From here I was able to read the wing tags – orange (faded red) with a white Z – Red Z, the big female who had been seen in the neighbouring glen a month earlier. The nest had a new female. The fate of A9/90 is not known, but I was still thrilled to see that Red P had managed to attract this new female and start afresh.

Typical spotting scope view from early monitoring of the Angus nest showing the difficulty of reading wing tags from this distance.

A few days later I returned to check on their progress and I hoped to catch a glimpse of the male, which I did, but he was not who I expected. A large bird came into view over the ridge and dropped rapidly into the valley then swept west towards the nest as Red Z called out in greeting. I couldn’t read the letter on the tag yet but I knew who this was. A single turquoise tag on the left wing could not have been more obvious as he banked sharply away from me and up onto the nest.

I watched in astonishment as Turquoise Z, the male from the Fife nest, landed on the edge of the nest. Red Z got up, let off a few more piercing calls and flew off in search of food. Turquoise Z then took his place on the eggs, settling in for a long shift.

Polygamy – when a single individual has multiple breeding partners – is not unknown in sea eagles but it is very rare, typically they mate for life. It was recorded a handful of times during the early years of the west coast release. In these cases a single male mated with two females on nests a few miles apart and it resulted in the failure of both nests on every occasion.

The demands of raising a chick make it almost impossible for a single male to provide enough food and take on enough of the incubation duties for two females. A single chick can require 1kg of food every day to keep growing and the adults themselves need 500g to stay healthy.

This nest in the Angus Glens is not just a few miles away from his usual nest in Fife; it is 28 miles as the eagle flies and at a higher altitude.

At this point we’d still not found the new nest in Fife; the Fife pair build a new nest every year, just a few hundred metres from the old one and they are usually finished building by January. I was not at all confident Turquoise Z would return to his usual mate, Turquoise 1, despite their success over the last four years, because of the large distance between the nests and was preparing to tell volunteers that there was unlikely to be a nest this year.

Dedicated volunteer and Fife native Richard Tough however was much more optimistic. He has watched these birds week in week out for the last three years and knew it would take more than a far flung affair to break their bond.

I set more of our volunteers the task of watching the forest in the hope of discovering the new nest site and they spotted Turquoise 1 carrying sticks into the same area of the forest where they have nested for the last three years.

We went in for one last sweep and found the new nest in a stand of trees I had searched just a few weeks earlier. She had built a new nest very late and very fast, just in the nick of time. On the west coast sea eagles have usually laid their eggs and started incubating by mid-March, at least two weeks before Turquoise 1 had started building.

There was still no sign of Turquoise Z, but on 9 April, Turquoise 1 started incubating eggs. A few agonising days later, Turquoise Z was at long last seen in Fife, flying into the nest and taking over incubation. It was finally confirmed – he had two females, two nests, four eggs and a lot of flying to do in between.

The first images of Turquoise Z at the Fife nest (top) making some last minute adjustments and at the Angus nest with Red Z just visible incubating. Both in early April 2017.

Over the last three months, a team of nest watch volunteers in Fife, Raptor Study Group members in Angus, RSPB Scotland and Forest Enterprise Scotland staff have watched both nests and I must take this opportunity to thank them publicly for all their hard work.

In Fife we have 30 volunteers watching the nest throughout the breeding season, recording their behaviour and ensuring the birds aren’t disturbed. This is not possible in Angus and we rely on a much smaller team of volunteers. The local famer also keeps an eye on the birds and any comings or goings of people near the nest.

During our observations a pattern started to emerge – Turquoise Z seemed to be alternating every other day between the two nests, travelling from Fife to Angus mid-morning. On several occasions he was seen leaving the Fife nest and arriving at the Angus nest between 60 and 90 minutes later. A long journey for this remarkable bird, who still had to take shifts incubating, provide food for both females and feed himself.

Even with this extraordinary effort the females had to take on much more of the incubating than they would normally. But they were up to the task and in May I got my first glimpse of two tiny, fluffy grey heads on the Angus nest, followed a week later by two more on the Fife nest. This is my favourite moment in this job, seeing the chicks for the first time and knowing they have safely made it through the precarious incubation stage where even a minor disturbance in cold weather can result in failure.

Turquoise 1 and the larger Fife chick at 4 weeks old in June 2017.

The chicks are still very vulnerable for the next three weeks however as they are unable to maintain their body temperature and need the parents to cover them and keep them warm when it’s cold or shade them from the sun when it’s hot, a behaviour known as brooding.

At some point in the first week after hatching one of the Angus chicks died, but the other flourished and continued to grow rapidly. On the Fife nest the chicks almost reached six weeks before one of them also died. It is quite rare for the second chick to die at such a late stage, indeed sea eagles often fledge two, but this has happened at the Fife nest for the last three years. Sadly it seems that one of the chicks becomes dominant and starts to outcompete the other for food.

Red Z at the Angus nest with surviving chick just visible behind her in June 2017, aged 7 weeks.

By July the remaining chicks, now one in each nest, reached eight weeks old. At this age they are almost full size but not yet able to fly, so this is when we fit them with satellite tags and wing tags. These are important tools for conservation as they allow us to study their behaviour – where they roost, where they hunt and even how they interact with other sea eagles. Three sea eagles from previous years that were fitted with satellite tags are still exploring East Scotland and giving us invaluable insight into how they spend their first few years of life.

The surviving chick at the Angus nest in early July aged 8 weeks, having just been put back in the nest after being fitted with wing tags “Blue V” and a satellite tag.

The female chick on the Angus nest was fitted with blue wing tags with a white V. The Fife chick, also female, was tagged with blue wing tags with a white X. At the time of writing they are 13 and 12 weeks old respectively and Blue V has taken her first tentative flight into an exciting new world. Blue X will surely follow within a few days. Given all they have known for their short lives to this point is a pile of twigs and branches two metres across, this must be quite an experience.

They are able to cover large distances using very little energy, thanks to their huge 2m wing span and their eye sight is one of the best in the animal kingdom. Combined with their social nature this makes meetings inevitable and all of the young sea eagles we have satellite tagged so far have met and spent time together. As long as they survive the difficult early months out on their own, it is almost a guarantee that Blue V and Blue X will meet each other before the end of winter, not knowing of course that they share the same father.

The surviving Fife chick, Blue X, during tagging in early July. Image credit Richard Tough.

These two nests are now connected by this curious quirk of behaviour, but it is striking how different their stories have been.

In Fife Turquoise 1 and Turquoise Z have bred successfully for the last five years, living alongside humans seemingly unperturbed by cars, planes, helicopters, dog walkers and everything else that comes along with us.

In the Angus Glens, far away from our towns and villages, the first three adult sea eagles that have been involved in breeding attempts have vanished along with one of the previous years satellite tagged juveniles – three more have disappeared elsewhere, also on grouse moors. The circumstances for each individual remain a mystery, but sea eagles usually pair for life so the pattern is hard to ignore, especially in light of the overwhelming evidence for satellite tagged golden eagles disappearing under suspicious circumstances on grouse moors.

There is cause for hope however. Already the presence of these sea eagles from the reintroduction in Fife has attracted birds from the much larger West Scotland population. Until 2016 all but one of the seven chicks fledged from East Scotland nests had died within their first year, but now three have reached this milestone and continue to do well. In another few years they may be building nests of their own.

  

Timings of the changes at the Angus and Fife nests, with the tiles representing individual adults.

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