31/08/2014 - CORMORANTS (Phalacrocorax carbo) IN THE RIBBLE CATCHMENT
CORMORANTS (Phalacrocorax carbo) IN THE RIBBLE CATCHMENT
Malcolm Greenhalgh
In recent years the numbers of adult Atlantic Salmon (Salmo salar) returning to the Ribble, and other rivers flowing into the Irish Sea coastline of north-west England and south-west Scotland, have greatly declined. Investigations are being carried out in an attempt to find the cause(s). One cause could be predation, of parr within the freshwater river and of smolts as they pass downstream, through the estuary, and north off the coast. The Cormorant is a potential predator.
SOURCE OF DATA
Prior to the 1960s little effort was made by amateur ornithologists in the region to make thorough censuses of the birds that inhabit the great estuaries of Dee, Mersey, Ribble, Morecambe Bay and the Solway. Then, from the mid 1960s, a small team that included me, made regular censuses of the Ribble estuary and Morecambe Bay (see, for instance, Greenhalgh 1975, Smith and Greenhalgh 1977, and Wilson 1973). This work was carried out because of plans to develop the Ribble estuary (by reclaiming the extensive saltmarshes) and Morecambe Bay (with a proposed barrage). The British Trust for Ornithology and Wildfowl & Wetlands Trust then joined forces to extend these surveys to include all the bays, estuaries and other wetlands of the British Isles in the WeBs survey.
Every year the Lancashire & Cheshire Fauna Society produced an annual report that includes observations from a wide range of amateur birdwatchers and the “official” WeBs data. These are the main sources used here, together with my own other observations and censuses. All quotes are taken from the appropriate year’s Report.
THE RIBBLE CORMORANT POPULATION, 1954-2012
1954: “14 Jan No fewer than 52 in the Ribble estuary...a record number from the area.”
1957: “seen every month at Lytham, with a maximum of 21, 13 December.”
1958: “11 May, one flying E.-W. Over Burnley, 10.45hrs.” This is the first published record that I have found from the (inland) Ribble catchment. 70 off Lytham, 2 March.
During the 1950s and 1960s Cormorants were present in the estuary in numbers peaking at fewer than 100 in the autumn-winter-early spring period, with single figures from April-July.
However, in the 1960s inland records became annual. For instance, the only record in the Ribble catchment in 1962 was “1 west over Leyland, 5 Feb.”; in 1963 the only one was “1 dead, near Burnley, 29 June (this was the first summer inland record); in 1965 the only record was one at Ribchester, 27 November. So by 1970 the Cormorant was a regular visitor inland, in single numbers, most records being in the winter months.
In 1970 there was evidence of a significant migration of Cormorants off the Lancashire coast when, on 24 January, 190 were counted heading north and 46 heading south off Freshfield, and when in 1973, 180 were counted from Formby Point. It was around this time that a roost of Cormorants developed in the docks at Seaforth on the Mersey estuary (see below). It was also in the 1970s that Cormorants established roosts at high water on the Ribble estuary, on Longton-Hutton Marsh at the confluence of the Ribble and Douglas and at Southport: e.g. at Douglas Mouth, 66, 31 December 1976; 49, 18 November 1975; 47, 13 March 1979, and at Southport 53, 30 January and 35, 15 March 1978.
Then, depending on the stage of the tide cycle, the saltmarsh roost moved sometimes onto Banks Marsh, which, being visible from Lytham promenade, sometimes resulted in the record of numbers “off Lytham”. The following are some counts of the Southport and saltmarsh roosts:
Southport Saltmarsh
1980 42 33 (Mar)
1981 45 (Jan) 92 (Nov)
1982 29 -
1983 52 (Nov)
1984 25 136 (Nov)
It was in this period, the late 1970s and early 1980s that Cormorants began to be recorded more frequently inland. The 1979 Report stated that they were, “Regular along Ribble in small numbers in the Preston area”, on 15 January 1982, 39 were counted at the confluence of the Ribble and Darwen at Walton-le-Dale, and by late winter of 1985 a roost had developed at Balderstone that held 56 birds on 20 February and with the last six birds there in April. In 1986 the Balderstone roost peaked at 63 on 15 March, two or three were present at Stocks reservoir throughout the year, and that year’s Report stated that, “in both winter periods” Cormorants were regular “upstream on Ribble, Hodder and Calder”.
Through the 1990s the increase inland continued, though slowly. For example, in 1990 Cormorants were recorded every month on the Ribble at Walton-le-Dale with a peak of 21 (February) and six throughout late spring and early summer. In 1993 the peak at Stocks was 24, it was recorded there every month except June, and in that year there were 58 records of Cormorants from 19 sites in East Lancashire.
It was in the mid 1990s that anglers became concerned at the increasing Cormorant population and so-called conservationists reacted to these concerns in a most unhelful way. In 1996, when 25 were counted on Parsonage Reservoir on 21 March and the Stocks Reservoir population peaked at 17 on 31 March, the editor of the Lancashire Bird Report argued that, ‘they are far from the “black plague” of some anglers’ fevered imaginings’. Sad.
Since then the following has been the status of the Cormorant inland in the Ribble catchment.
At Stocks Reservoir the peak has averaged (2000-2012) 58, and although the peak has occurred in autumn or early spring, numbers are present all year. Some of the food of these cormorants comes from the reservoir, but birds flight daily elsewhere in the catchment and it seems that some feed in the Hodder, if not also the Ribble, downstream of the reservoir.
At Brockholes (the Wildlife Trust Reserve at Salmesbury) the population has peaked at 51 (in March 2003 and November-December 2004). These birds mostly head elsewhere inland to feed.
Woodland roosts have been recorded at several places. I have already mentioned the roost at Balderstone. Others include: Hurst Green (maximum 37 in 2008), Lambing Clough Wood (26 in 2007), Calder Wood (19 in 2007). Again, these are birds that feed on rivers and reservoirs within the catchment.
As the 2007 Bird Report stated, “virtually all Lancashire water bodies hold at least a few [Cormorants] at some time during the year.”
The increase of the Cormorant population on the Ribble estuary (2000-2012)
The following are the monthly averages for 2000-2004, 2005-2009, and 2010-2012:
JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC
’00-’04 194 206 202 83 14 10 39 89 196 290 231 409
’05-’09 317 281 209 109 74 46 96 120 252 291 422 307
’10-’12 677 727 843 340 242 210 341 344 611 1039 1301 1580
The increase, and especially a very recent great increase, is quite marked, especially when the annual peaks are compared for the years 2005-2012 (month of peak in parathenses):
2005: 543 (January)
2006: 289 (February)
2007: 397 (December)
2008: 623 (November)
2009: 659 (November)
2010: 946 (November)
2011: 1197 (November)
2012: 3297 (December)
This increase on the Ribble estuary is a part of a massive increase throughout the north-west’s estuaries and bays. In 2011-12 (the last years for which I have records) the Dee estuary Cormorant population peaked at over 3000, Mersey over 400 (the Mersey formerly held far more, but their population seems to have moved north, to Ribble, Morecambe Bay and Cumbrian coast, due, according to the 2012 Lancashire Bird Report, to “a change of favoured feeding areas within Liverpool Bay, away from the Burbo Bank towards the outer Ribble. The combined December [2012] WeBs count in the English sector of Liverpool Bay on the Ribble and at Formby Point, Seaforth and Hilbre Island [Dee estuary] totalled 4973, 14% of the British and 4% of the western European populations.” Add to that, in 2012, in the order of 3000 Cormorants spread from Morecambe Bay to the Solway, and the impact on fish swimming through inshore waters must be great.
A Conclusion
Ten years ago the Sea Bass population of Ribble estuary was great (I once caught nine in an hour from one of the estuary training walls!); today, I am informed (by Phill Williams) that the Bass population has collapsed, and stocks of other inshore fish species similarly low. I cannot see how, in 2010, 2011 and 2012, a May-June average population of over 240 Cormorants cannot have a serious effect on the Ribble salmon smolt run, for the smolts must pass downstream through a channel 110 metres wide, 25km long that is shallow and with a flat sandy bed as they pass out from Preston to the sea. There is no hiding place and, from my observations from a salmon netsman’s boat, Cormorants feed keenly through the ebb in the estuary channel, the time when the smolts are running.
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