Tuesday, January 26, 2016 at 11:55AM Maximum winter counts from all sites counted for the Wetland Bird Survey in Pembrokeshire. Data after 2000 includes the Teifi Estuary.
Main wintering sites for this species are the Cleddau Estuary, Bosherston Lakes, and Llys-y-fran Reservoir. However, large numbers can occur elsewhere, for example 50-60 in Fishguard Harbour in early 2015.
Saturday, September 14, 2013 at 8:55AM Phalacrocorax carbo carbo
Common resident. Found on inland waters, autumn to spring. Mathew gives the following breeding stations: Ramsey, Skomer, Lydstep Head (20-30 pairs), at Pointz Castle (where they drove out Herons), and in trees at Slebech. These still exist but the colonies fluctuate (eg the colony on the Mewstone, Skomer was apparently deserted in 1898 and in 1947). Other colonies: St Margaret's Island, St Bride's Stacks, Pwll Deri and Newport Head.
R.M.Lockley, G.C.S.Ingram, H.M.Salmon, 1949, The Birds of Pembrokeshire, The West Wales Field Society
Monday, May 7, 2012 at 4:27PM The largest colony of Cormorants is on St Margaret’s Island and this is one of the best studied in the UK, with almost continuous census data for 50 years and over 5,000 chicks ringed since the mid 1960’s. There are smaller colonies on Thorne Island (it relocated from Sheep Island in the early 1990’s), on the Mew Stone, Skomer, at times on Stack Rocks off Little Haven, on the Green Scar at Solva, around Dinas Island and at Cemaes Head. Occasionally pairs might nest at scattered mainland sites. There are many coastal drying out sites (including jetties etc in the Milford Haven Waterway) where sometimes good numbers of birds can be seen.
The Cormorant population fluctuates from year to year, as probably in poor springs some birds fail to breed. Overall counts show there was a tendency to a decrease during the 1990’s but a modest increase again in the early 2000’s. The total population in the county in 1984-88 survey was around 300 pairs and a census following the Sea Empress oil spill (1996) found 360 pairs, with 180 of these on St Margaret’s Island. The population during the most recent years appears to have been stable and may have increased slightly.
The highest county population was almost certainly in the early 1970’s, when around 450 - 500 pairs probably bred, 330 of them on St Margaret’s, but the reasons for the subsequent decrease are poorly understood. Breeding success varies from year to year but there are few years of substantial failure. Ringing has shown that considerable numbers are shot on rivers or killed in coastal fishing nets during the winter period. It seems likely that this is a major cause of population changes.
Steve Sutcliffe
Fieldwork 2003-07 (based on 490 tetrads)
Red = breeding confirmed = 13
Orange = breeding probable = 2
Yellow = breeding possible
Total tetrads in which registered = 15 (3.1%)
Sunday, December 11, 2011 at 8:27PM Breeding resident
Mathew (1894) noted Cormorant colonies at Ramsey, Skomer, Lydstep Head and Pointz Castle, Lockley et al. (1949) adding St Margaret's Island, St Bride's Stacks, Pwll Deri and Newport Head.
In 1969, during Operation Seafarer, 378-388 pairs were found breeding, while the Seabird Register of 1985-1987 found 362 pairs, so the population has remained fairly stable despite variation in the sizes of individual colonies. Cormorants are seen throughout the year with the colonies usually occupied from February to September, ranging from single pairs breeding on cliff sites to the largest colony in Wales at St Margaret's Island, which held 322 nests in 1973, but 230 pairs in most years since (see Table 2). Mathew (1894) recorded nesting in trees at Slebech.
Ringing at St Margaret's Island has shown that some birds remain in Pembrokeshire waters throughout the year but others, mainly immatures, move up the Bristol Channel during the winter, or along the length of the English Channel and into the Bay of Biscay as far as the Iberian peninsula. Some pass inland to the Thames Valley, a few reach Ireland and North Wales and one has been recovered in Holland. Additionally, each autumn strings of up to 20 birds are seen passing down through the southern Irish Sea and St George's Channel from the north, and Irish‑bred birds have been noted at St Margaret's Island.
Cormorants fish extensively in the shallow bays around the Pembrokeshire coast, penetrate all the estuaries and rivers and regularly frequent the larger inland waters such as Llysyfran reservoir, besides visiting quite small pools on an opportunistic basis. Winter roosts of up to 47 birds include several breeding sites but they also roost elsewhere, notably in trees at Llysyfran reservoir, Slebech and Femhill.
Fieldwork 1984-88 (based on 478 tetrads)
Red = breeding confirmed = 13
Orange = breeding probable = 1
Total tetrads in which registered = 14 (2.9%)
Donovan J.W. & Rees G.H (1994), Birds of Pembrokeshire
Friday, November 11, 2011 at 10:31AM 
Red = breeding confirmed
Orange = breeding probable
Yellow = breeding possible
Friday, September 16, 2011 at 12:07PM 
The BTO winter atlas showed that Cormorants were present in most coastal and estuarine 10km squares and on some inland waters during the winters of 1981-82, 1982-82 and 1983-84.
The darker the colour, the higher the relative total count for each 10km square. The darkest blue represents over 25 birds.
Graham Rees
Tuesday, December 28, 2010 at 6:30PM Species account from M Mathew, 1894, "The Birds of Pembrokeshire and its islands"
