Montagu’s Harriers set UK longevity record
The two Montagu’s Harriers ringed as chicks in Dorset in 2004 were caught this year by the RSPB and become the oldest known birds to be seen in the UK. They announced the news in their 2017 breeding season roundup in which we also found out that only five nests were located, meaning the Montagu’s Harrier population is still teetering on the edge.
Here is the full update from the RSBP
During the 2017 breeding season five Montagu’s harrier pairs were located; four were successful and produced a total of 12 fledged youngsters. The fifth pair nested (SW England) but failed after the un-tagged male disappeared for unknown reasons.
One of the nests was a relay, as the first clutch was predated whilst at egg stage. One pair was in Norfolk with four pairs elsewhere in England. Sally, the satellite-tagged Norfolk adult female, which was featured on BBC Winterwatch vanished in questionable circumstances recently - read our blog here.
Once hatched all four nests were fenced to stop predators and enable farming operations to continue without any accidental damage. Harvesting successfully took place at all four sites before any of the juveniles were flying.
All the juveniles were fitted with unique lettered Darvic rings, bringing the total to 25 juveniles fitted with rings over the past two years. This should prove invaluable in calculating return rates and site fidelity. Amazingly we have already seen a juvenile ringed in SW England on 20th July (with the letters 'FX') sighted abroad, in Holland at Vlieland on 21st August, an amazing movement and a surprising direction. Another ringed juvenile bird seen at Winterton, Norfolk last week was from the same brood in SW England but frustratingly the full ring details could not be seen. We urge birders to look out for these rings on any Montagu’s harrier they are fortunate to see, sighting can be reported to montys@rspb.org.uk.
Four birds previously satellite tagged in England returned to breed including Mark (2014), Roger (2015), Beatrice (2016) and Sally (2016). Mark is the longest standing harrier that we have tagged and it was frustrating this year that the aerial from his tag came off, affecting his signals but not his ability to father four more juveniles. In partnership with the Dutch Montagu’s Harrier Foundation three new adult birds were satellite tagged, males James and John and female Ruth, this work was again kindly sponsored by The Sound Approach.
The undoubted highlight of the year was the catching of two new adult female birds - Ruth and ‘GL’. Both were found to be wearing BTO metal rings and incredibly are sisters from the same brood of chicks ringed in Dorset in 2004! - when they were filmed being ringed by Chris Packham as part of a BBC Inside Out TV programme!. Ruth hadn’t been specifically seen since 2004 but we know that ‘GL’ had toured around southern England for a few summers, had attempted to nest on the Humber in 2015 and has been breeding successfully in SW England for the past two summers! These are sensational harriers and if wintering in Senegal then they will have each flown around 65,000 miles on migration alone!
This really is a watershed moment - proven UK born juveniles returning to breed and surviving 13 years.
Not only have both of these birds set a new UK longevity record but together with the fact that all of our returning satellite-tagged adults have returned to their previous years breeding sites this shows we have a defined UK population which requires continuing conservation effort.
In trying to understand how we increase the UK population we now have to solve the final piece of the jigsaw - what happens to the bulk of our fledged juveniles? where do they winter? when do they return back to breed ? how many die ? where ? when? and why? We will be working on this next year!
In the meantime you can follow the latest news of the adult birds on migration at UKmontagus on Twitter, we will provide daily updates once the birds have left the UK.
6 September 2017
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