Wintering Hen Harriers on Birsay Moors RSPB Reserve

One of the most enjoyable parts of my job on reserves during the winter months is carrying out a monthly count of wintering Hen Harriers using the Birsay Moors reserve communal roost. Selecting the right day weather wise is crucial as it can be a bitterly cold/damp session otherwise. Generally we try and arrive on site about an hour before sunset, with bird activity peaking around 15 minutes either side of sunset.  Concentration for this survey work is key and keeping track of birds when they come in from any angle can be difficult at times as they quite often settle somewhere as if to take stock of who else is about before then settling for the night in a grassy gap in the dense heather. Quite often two of us will observe the harriers at dusk, which helps. We are very fortunate on Orkney having several traditional roost sites used across the county and indeed in recent years a few smaller sites have been found.

 
Ring-tail female Hen Harrier - Andy Hay

On the 27th Jan I decided to do an interim visit to Birsay as the weather was suitable to count the harriers. I arrived at 1530hrs and the first ring-tail bird (ring-tail is the general term for a female or young male, which show a white crescent at the base of the tail/rump) appeared at 1547hrs. During the next hour I was treated to a minimum of 20 birds (8 grey males and 12 brown ring-tails) coming to roost on the hillside, with the last bird entering the roost 27 minutes after sunset which was at 1620hrs. The males tend to gather on the outskirts of the roost before entering themselves satisfied that the coast is clear or perhaps waiting for certain ring-tails to arrive, who knows? The short flight from their vantage point ends with a twist plunge dive to the ground and the show is over...

Pair of Hen Harriers - Mike Langman

Not much else seen that night in terms of other species but, occasionally other raptors are recorded with Buzzard, Peregrine, Merlin, Kestrel & Sparrowhawk all being seen this winter. More frequently are sightings of Short-eared Owls which come out at dusk to feed and they seem to revel in harassing the Hen Harriers before they have settled for the night. On occasions up to 4 Short-eared owls have been recorded. A large congregation of Hooded Crows roost in a nearby reedbed with between 60 - 100 birds at times.


Male Hen Harrier - Andy Hay

The Hen Harrier Winter Roost Survey (HHWRS) has been running continuously since its instigation by the late artist and ornithologist Donald Watson and harrier enthusiast Dr Roger Clarke in the early 1980s.