Tuesday, 15 April 2014

Langholm Harriers

Many thanks to Stephen Murphy at Natural England for this update:

10th April
 I hope you have enjoyed keeping up with the birds since they fledged in July 2013 but as they have recently moved to where they may breed, the updates will continue with text only. Should any of the tracked birds move significantly then updates will recommence as usual.
All birds as they were in last update.
Miranda, or maybe O’Miranda, as she has spent more time in Ireland than her native Scotland, is still in County Mayo, approximately 457 km from her sister Grainne and near neighbour Hattie in Langholm, Scotland. A recent note kindly sent by Irene O’Brien may give a hint at why Miranda is staying in Mayo – “There has been a male seen roosting in the area over the Winter....It would be great if she stayed around, I don't know why hen harriers don't breed up here as there is plenty habitat for them”. It is interesting that Miranda did not use the nearest communal roost (B. O’Donoghue pers comm), this information suggests it is good habitat and prey availability that is holding her, as opposed to finding a mate and breeding. All can change quickly though and it may only take a passing male or a philopatric pull of home to get her on the move.
I was informed today that Hattie and Grainne were skydancing and nest building, so all being well they will attempt to breed in the next few days. I know, do not count your chickens but if the tracked females are successful and transmitters are fitted to their young, it will only be the second time that a parent and young harrier have been satellite tracked together. This is the best method for investigating whether the parents play a role in juvenile dispersal and for assessing sociality between tracked individuals (Jacobs Index). The transmitters will also provide data to map the parent females range as they start to hunt for their growing young.
That Hattie and Grainne have overwintered in the Langholm area is testimony to the management in place. It is vital that birds of local provenance along with any immigrant birds can find a safe haven for wintering and breeding in the Langholm area. It is important that birds such as Hattie and Grainne breed at Langholm, as lack of recruitment is the main reason the harriers have not increased as in the JRS.
With any luck, over the next few days, the fixes for the Langholm females will start to contract, and then clump on one circular spot, measuring about 60cm across, made of heather, lined with fine grass.

On the 13th April Miranda left the area she has been loyal to for 25 weeks and flew 75km to the east into Sligo before making a u-turn and returning towards County Mayo. By her recent standards, this was a significant journey. The distance covered over time was more similar to a migrating harrier. So has that natal pull kicked in, has she followed other harriers heading east, or was it just a bird prospecting around? We will know tomorrow.
The most recent run of data covered the 13th of April from early hours at roost near Carrowmore Lake in County Mayo to the last fix was at 11.50 am heading west back towards Mayo, for all we know (now) she could now be back at Carrowmore.
Fig 1 shows the places we know she visited during the 10 hr transmission period because it is based on fixes guaranteed to be within 250m of the birds actual location. Fig. 2 shows the same data set without filtering including two fixes over sea at 09.43hrs and 10.11 hrs. These low class fixes could be accurate and probably shows a more realistic route taken.

Skydancing male Hen Harrier John Wright

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