RSPB Scotland’s Investigation Intelligence Officer Jenni Burrell provides an update on Mannin, the Isle of Man sat-tagged hen harrier.
Monitoring satellite-tagged hen harriers can bring many positives – following an individual bird from the day it was fitted with a transmitter until its first flights away from the nest area, its travels through the UK (and beyond in some cases) or even hopefully until its own first nesting attempt. Unfortunately, however, it can also bring some negatives. Sadly, here, we report on the death of another of our 2017 birds.
Mannin, along with his sister Grayse, was tagged on the Isle of Man on 3rd July 2017 by trained & licensed members of the Scottish Raptor Study Group and Manx Ringing Group in partnership with Manx Birdlife. After fledging in July, Mannin explored his home island until 14th August, when the tag data showed he had departed the island and headed north towards the Galloway coast in SW Scotland. Sadly he never completed this journey, and the data showed that he had gone down in the sea, approximately 5km off the Scottish coast.
Mannin and sister Grayse - image by James Leonard
We have not lost one of our tagged birds at sea before, and while we were almost certain he had died, we were unsure if the tag would continue to function or when we would eventually lose track of Mannin, if the voltage in the tag’s battery declined or if his body sank to the bottom of the sea?
A few days later, on 24th August we had our answer. The satellite tag had continued transmitting, and the data showed that Mannin was now located on the shoreline. After a brief search of the area, near Kirkcudbright, my colleagues soon found Mannin’s remains and the tag. As with all recovered birds we submitted his body for examination, at the SRUC Veterinary Laboratory. Their subsequent post mortem report said that there was no evidence of trauma or health problems and that Mannin had eaten a small mammal recently.
We’ll never know what caused Mannin to go down in the sea. Maybe he was caught in heavy rain, and with nowhere to land, became waterlogged and was unable to complete the sea crossing? Whatever the cause, it was a sad end to his short life.
Map of Mannin’s movements
Sadly, Grayse has also died, also just a few weeks after fledging. She was recovered on the island on 9th August after her tag showed that she had died. Her body was examined by ZSL whose interim diagnosis did not implicate human interference as a cause of death.
Neil Morris from Manx Birdlife said “Obviously, everyone involved in the project here in the Isle of Man is desperately sad that Grayse and Mannin have perished. Their early demise highlights the vulnerability of young birds learning to fend for themselves once they have fledged the nest. It also underlines the need for a large healthy population that can withstand such losses.
“At the same time, it’s wonderful to see Aalin coming through her first year so well, and to get such an insight to her behaviour. We need to know so much more about these wonderful birds of prey in order to formulate ever better conservation strategies. We shall continue the work to study Hen Harriers on the Isle of Man.”
Whilst the deaths of both of these birds through natural causes is disappointing, the finding of their bodies and recovery of them and their tags was straightforward. As you would expect, their transmitters continued to provide us with good location data, even after one of them had spent ten days in the sea.
This is, however, in marked contrast to the disappearance of “Calluna”, whose perfectly-functioning tag’s transmissions ended very abruptly on 12th August. Her last recorded position was on a grouse moor, a few miles north of Ballater, in the Cairngorms National Park, and her disappearance can rightly be regarded as highly suspicious.
Here’s hoping that the ten remaining birds from the Class of 2017 continue to thrive and provide us with many more positive stories. You can follow them here.
RSPB Scotland’s Investigations Intelligence Officer Jenni Burrell introduces the new class.
This year the Hen Harrier Life Project website has been improved to provide a more interactive experience for visitors. You can choose to look at individual birds, track their journey and look at any points of interests that appear.
The profiles of twelve of this year’s satellite-tag hen harriers are now online and what a brilliant bunch they are. Take a look on the website to learn more about their stories and meet:
Calluna (image by RSPB)
Eric (image by Alan Leitch)
Heather (image by Brian Etheridge)
Lia (image by Guy Anderson)
Mairie (image by Paul Howarth)
Mannin (image by James Leonard)
Manu (image by Tim Jones)
Rannoch (image by Brian Etheridge)
Saorsa (image by Brian Etheridge)
Skylar (image by RSPB)
Sirius (image by RSPB)
Tony (image by Dave Anderson)
Sadly Calluna is no longer with us. Calluna’s sat tag transmissions abruptly ended on 12th August, with no further data transmitted. Her last recorded position was on a grouse moor a few miles north of Ballater, in the Cairngorms National Park - Jeff Knott has written this blog about her.
You’ll be able to follow the progress of the other birds as we map their movements online. To protect sensitive breeding sites, maps of their movements will only be added as soon as they’ve dispersed away from their nest sites. We have already been able to share the first movements of Heather, Eric, Skylar, Sirius and Saorsa who have already proved to be adventurous and spread their wings. We’ll add the remaining birds as soon as we can.
You may notice that only one of last year’s birds is back on the website. After a very successful breeding season, DeeCee has moved away from the nest site so we are able to share her movements again. Don’t worry, the other four are safe and well, but have yet to move away from breeding areas. We will keep you updated and will begin to map their movements in due course. In the meantime, see what they have been up to in a previous blog.
It’s going to be an exciting year following these birds and seeing what they get up to and we can’t wait to share it with you.
I’m very sad to have to report that one of the hen harrier’s satellite tagged as part of the LIFE project this year, has already disappeared.
“Calluna”, a female harrier, was tagged this summer at a nest on the National Trust for Scotland’s Mar Lodge estate, near Braemar. We were monitoring her transmitter’s data which showed that she fledged from the nest in July. She left the area in early August, and gradually headed east over the Deeside moors. However, while the tag data showed it to be working perfectly, transmissions abruptly ended on 12th August, with no further data transmitted. Calluna’s last recorded position was on a grouse moor a few miles north of Ballater, in the Cairngorms National Park.
For regular followers of our hen harriers, this will be a depressingly familiar story. I’m sure some will focus on the date transmissions ended – the 12th August, the traditional start of the grouse shooting season. Bluntly, the date isn’t really the point. The disappearance of one of our hen harriers is a major loss whenever it occurs.
While we will likely never know for certain what happened to Calluna, it fits a pattern of disappearances where perfectly functioning tags suddenly stop transmitting and are never recovered. She joins the growing list of satellite-tagged birds of prey that have disappeared, in highly suspicious circumstances, almost exclusively in areas intensively managed for grouse shooting. The transmitters we use are incredibly reliable and the sudden halt in data being received from it, with no hint of a malfunction, is very concerning.
I started working on hen harriers for the RSPB 10 years ago next month. One of the first documents I helped produce discusses how terrible it was that there were only 14 successful hen harrier nests in the whole of England that year. This year there were three. It’s appalling to me now that those historic 14 successful nests in one year would be treated like a breeding bonanza today!
But despite that lack of progress and the continued disappearance of hen harriers like Calluna, I remain optimistic. More people know more about the plight of these amazing birds than ever before. In Scotland the Cabinet Secretary for the Environment has commissioned an independent group to look at how grouse moors can be managed sustainably and within the law.
And there are still lots of other young hen harriers out there with satellite tags on, thanks to the LIFE project. The team has fitted a significant number this year, with the very welcome help from landowners, including the National Trust for Scotland, who value these magnificent birds breeding on their property. You will be able to follow the trials and tribulations of some of those birds very soon. Check back here for more news. These tags help us not only better understand and protect hen harrier, but also bring new voices into the fight to save them.
Hopefully no more of our hen harriers go the way of Calluna.
If anyone has any information about the disappearance of Calluna we urge them to contact Police Scotland as quickly as possible.