Circus cyaneus – BOD TINWEN – Scarce passage migrant, winter visitor and former breeder.
The Marsh Harrier breeds throughout the Western Palearctic, wintering southwards as far as Africa but it is resident in some areas.
Said to be formerly a common resident in Pembrokeshire, it had become a rare visitor by the time of Mathew (1894). How rare can be judged by there being only eight recorded occurrences between 1880 and 1941. Eighteen individuals were noted between 1942 and 1980, an increase that cannot be entirely due to a growth in the number of active observers.
From a single pair in 1971, the British breeding population increased by about 20 % per year to reach a minimum of 363 pairs by 2005. Although Pembrokeshire is peripheral to the main breeding area in eastern England and the species remained scarce in the county, its frequency of occurrence increased during the British population expansion.
A pair summered in both 2010 and 2011 but breeding was not proven.
Cumulative monthly totals up to 2011.
Peak passage periods were April and May in spring and August and September in autumn. Apart from one seen near St David’s on the 2nd January 1955, there have been two over wintering birds, at the Dowrog in 1982/83, Marloes Mere in 1994/95 and at Castle Martin in 2009/10.
The only adult males recorded were: at Stone Hall in 1880, Ramsey on 20th May 1953, Skomer on the 3rd April 1984 and 24th – 25th April 1997, Trefeiddan on the 8th April 1984, the Gann on the 2nd March 1994 and 29th March 1995, Skokholm on the 3rd May 2001, Hendre, St David’s, on the 4th May 2001, the Dowrog on the 13th November 2003 and one half of the possible breeding pair in 2010 and 2011.
Most Marsh Harriers recorded were at or near the coast, from the Ceredigion border to Tenby, most frequently at the Teifi Marshes, St David’s area, Skomer and Marloes Mere.
Records from further inland were: Stone Hall in 1880, shot at Loveston in c.1884, Jordanston Moor prior to 1894, Mynydd Preseli on the 14th August 1929, Thornton on the 12th May 1971, Treffgarne on the 29th September 1996, Clarydale on the 15th April 1997 and Haverfordwest Race Course on the 10th October 2002. It should be noted that the bulk of observer attention has been focussed on the coastal strip.
Marsh Harriers seen migrating through the county have often hunted on the way, particularly pausing at wetlands, heath and moor but have also been seen quartering barley fields. Many followed the line of the coast but one was seen flying northwards out to sea at Strumble Head on the 6th May 2001 and another coming in off the sea from the north on the 3rd November 1996. A female was seen to depart eastwards from Marloes Mere on the 26th April 1987 steadily gaining height and was at an estimated altitude of 500 feet when finally lost to sight.