SeaWatch SW is a volunteer-based project that started in 2007 and is scheduled to run until 2011 at least. The main aim is to understand better the distribution and behaviour of migratory marine megafauna, both for scientific and conservation purposes. The priority is the Critically Endangered Balearic Shearwater, but other migratory seabirds as well as Basking Sharks, Ocean Sunfish and cetaceans are the focus of intensive monitoring off southwest England.
Part 1: Balearic Shearwater monitoring in UK and Irish waters
A total of 983 Balearic Shearwater records were received from the UK and Ireland in 2009, relating to a maximum of 4824 birds. Numbers reported over the three years 2007–09 have therefore remained stable, with the number of records averaging about 900 (±100) per year and the maximum number of birds seen averaging about 5100 (±300) per year. It should be noted that these maximum totals will include significant duplication, as some birds may remain in an area for several days or are recorded passing multiple watchpoints.
The temporal distribution of Balearic Shearwater sightings in 2009 was comparable to 2007 and 2008. The now expected midwinter influx into southwest England was noted in January, but very few were then seen until birds began returning to southern England in May. The June total was lower than expected, but numbers rapidly increased to a peak between July and October. Regular records came from southwest England up to mid-December, but few were seen elsewhere in the late winter.
As with previous years, about two-thirds of records came from southwest England, particularly Cornwall, Devon and Dorset. About 9% of records came from Ireland and 7% from Wales, with less than 2% from Scotland. Sightings away from southwest England peaked in August and September. The highest day total was a record Devon count of 145 off Berry Head on 2 Sept. Overall, the spatio-temporal distribution of Balearic Shearwater sightings in 2007–09 has been remarkably consistent.
Part 2: Land-based monitoring from Gwennap Head (Cornwall)
Effort-based monitoring of all seabirds, cetaceans and other target species was undertaken at Gwennap Head (Cornwall) between 15th July and 15th October 2009. About 40 volunteer observers helped man the watchpoint for 93 consecutive days, with 'dawn-to-dusk' observations totalling almost 1000 hours for the third year in succession. It was another unsettled summer in Cornwall, with a dominance of strong winds veering between southwest and northwest in July and August, but more settled and variable conditions in September and October.
Balearic Shearwaters were seen on 90 out of 93 survey dates (same as 2008), with a maximum total of 1422 birds recorded. Totals over the three years 2007–09 have therefore averaged about 1200 (±225). It is likely that some birds are recorded on multiple dates, but these results indicate that overall passage rates over the three years have remained consistent. The pattern of movement was also very similar to previous years, with most birds (96%) flying west and 61% seen during morning sessions. The peak day counts were 78 on 4th October and 91 on 12th October.
SeaWatch SW observers at the Gwennap Head watchpoint (Photo: Russell Wynn)
It was a bumper year for rare seabirds during the Gwennap Head survey, with the highlight being a first- or second-year Black-browed Albatross moving west close inshore on 26th July (the first in Cornwall for over 20 years). Two Wilson's Storm-petrels were then seen foraging offshore with European Storm-petrels on 1st August, during an unprecedented influx into the region. Three sightings of Fea's-type petrels were made between 30th August and 2nd September, with at least two different birds thought to be involved. Finally, there were three sightings of Yelkouan-type shearwaters during August, and the SeaWatch SW team is currently leading efforts to establish the specific identification and origin of these birds (see below).
Totals of other shearwater and petrel species seen during the Gwennap Head survey included 27,508 Manx Shearwaters, 527 Sooty Shearwaters, 509 European Storm-petrels, 31 Cory's Shearwaters and seven Great Shearwaters. Numbers of Manx Shearwaters, Sooty Shearwaters and European Storm-petrels were very similar to 2008, but there was no repeat of the Cory's Shearwater influx of that year. The peak movement of Sooty Shearwaters was 109 on 2nd September, coinciding with record numbers seen further east.
Numbers of Arctic Skuas, Kittiwakes, Sandwich Terns and Common/Arctic Terns were markedly lower than in previous years, although Great Skua numbers remained stable. The main passage of Arctic Skuas and Kittiwakes in early October was again synchronised, but was significantly lighter and later than in 2007 and 2008. Numbers of Guillemots and Puffins have increased progressively over the three years, whereas Razorbill numbers have remained stable.
Records of scarce seabirds included single Goosander, Red-necked Grebe, Leach's Storm-petrel, two Sabine's Gulls, two Yellow-legged Gulls, three Black Terns, five Little Gulls, seven Grey Phalaropes and 16 Pomarine Skuas. The total of 84 Mediterranean Gulls is a further increase, and is presumably related to increased dispersal of birds from the rapidly growing breeding population in northwest Europe.
Migrant waterbirds seen offshore of Gwennap Head included 14 Grey Herons, 17 Little Egrets and 91 Whimbrel. Migrant land birds found by SeaWatch SW observers around Gwennap Head and nearby Porthgwarra Valley included a fly-over Purple Heron on 16th September, two Marsh Harriers, several Merlins, and a juvenile Hobby and a Woodcock in off the sea in October. Small birds included Dartford Warbler, Firecrest and Pied Flycatcher. Two Choughs were seen on four dates. A juvenile Peregrine was seen unsuccessfully attacking a number of seabird species offshore, including Black-headed Gull, Kittiwake, several Razorbills and even a Balearic Shearwater!
Six species of cetacean were observed during the Gwennap Head survey. Harbour Porpoises were regularly encountered, being seen on about two-thirds of survey dates. The maximum total of 412 animals is very similar to the 2007 and 2008 totals. Minke Whales were seen on 20 dates, with a maximum total of 46 animals recorded. This total is also comparable to previous years. Both species were regularly observed foraging in the tide race around the margin of Runnelstone Reef.
Common Dolphin numbers were higher than in 2008, with a maximum total of 684 including a superpod of at least 200 in mid-August. Both Risso's and Bottlenose Dolphins continue to make sporadic appearances, and were seen on six and ten dates, respectively. The cetacean highlight was probably a pod of 20–25 White-beaked Dolphins moving west on 10th October: the first record in almost 3000 hours of survey effort at this site and one of the largest pods in Cornwall in recent years.
Numbers of Grey Seals using the haul-out to the west of Gwennap Head remained stable, peaking at 18–20 animals on several dates. A clear cyclic pattern to the numbers using this haul-out is emerging, related to the fortnightly spring–neap tidal cycle. Prey items included wrasse, mullet, bass and even a Conger Eel! A maximum total of 20 Ocean Sunfish were seen, a reduction on previous years. Most sightings were made in July and August.
It was a very poor year for Basking Shark sightings in southwest waters during the survey period, presumably linked to the dominance of unsettled weather conditions. A maximum total of 71 surface sightings were made off Gwennap Head, almost an order of magnitude lower than the 2007 total. Few were seen in July and August, with a peak in September for the third year in a row. The highest count of animals seen at the surface simultaneously was just 12 on 25th September. There was just one record of breaching in 2009.
Other notable wildlife recorded at Gwennap Head included a buck Roe Deer on the cliff edge on 20th July, and a small specimen of Portuguese Man-o-War washed up in the adjacent cove on 29th July. This stranding was one of many of this species in the southwest UK in late summer 2009, related to the dominance of strong south and southwest winds at this time.
Visual monitoring data are providing increasing evidence that the Runnelstone Reef, offshore of the Gwennap Head watchpoint, is an important foraging area for a range of species. The visible tide race around the reef margin regularly attracts feeding seabirds (e.g. Manx Shearwaters, European Storm-petrels, Gannets, Herring Gulls and Puffins), cetaceans (especially Harbour Porpoises), Grey Seals and Basking Sharks, with occasional Balearic Shearwaters and Minke Whales also utilising this habitat.
Basking Shark feeding along a froth line off Gwennap Head, with the dorsal fin, tail fin and white inner mouth all visible. (Photo: Russell Wynn)
As with previous years, small-scale disturbance by boats and kayaks was noted off Gwennap Head on multiple dates. Grey Seals and Shags were disturbed from their low-tide haul-out and roost site by kayakers, while Basking Sharks were seen being closely pursued by leisure craft. On one occasion, a group of snorkelers was seen to surround a Basking Shark to within touching distance, although the shark appeared to be relatively unaffected and continued surface foraging. The small fleet of local fishing boats was again seen to have negligible impact on any of the survey target species.
Part 3: Land-based observations from sister sites
Timed observations were carried out at five sister sites, totalling over 1200 hours of observations. Data from four sites in the southwest UK (Berry Head in south Devon, Pendeen and Trevose Head in northwest Cornwall and Strumble Head in Pembrokeshire), help to put the Gwennap Head sightings into a regional context. Whitburn in northeast England is contributing data that may help link seabird migratory movements between the North Sea and western English Channel.
The total numbers of target species seen from the six SeaWatch SW watchpoints are tabulated below. The upper summary table shows the total number of seabirds and cetacean/fish recorded, while the lower table shows the rates of birds per hour, although only those species passing at rates >0.2 birds per hour are listed:
Total numbers of target species recorded
|Total hours||998.5||135.5||144||118||478||343||Balearic Shearwater||1422||379||276||149||122||12|
|Great Northern Diver||9||0||0||3||0||7|
Passage rates in birds per hour
|European Storm Petrel||0.51||0.12||3.91||0.33||0.18||0|
The above tables reveal some interesting patterns, although variable effort between sites means direct comparisons should be treated with caution. Only the data from Gwennap Head are effort-based, i.e. fixed hours every day during the survey period. Despite these limitations it is clear that Balearic Shearwater passage rates were fairly consistent across southwest England (1.3–2.8 birds per hour), with lower rates off Strumble Head and very few off Whitburn.
Passage rates of wildfowl, e.g. Common Scoter, and terns are much higher off Whitburn than off the southwest UK, although numbers of skuas are comparable between regions. Manx Shearwaters and Guillemots/Razorbills are most abundant off Strumble Head and northwest Cornwall, which are in close proximity to major colonies. The high passage rate of Common Scoters off Strumble Head, compared to sites off northwest Cornwall, is due to birds moving to wintering grounds in Carmarthen Bay (south Wales) where 40,000 were counted in February 2010.
Eiders passing the sister site at Whitburn (Photo: Mark Newsome)
Looking at year-to-year variations at those sites with sufficient data (Gwennap Head, Berry Head, Trevose Head and Strumble Head), it is clear that passage rates of Arctic Skua, Kittiwake, Sandwich Tern and Common/Arctic Tern were lower in 2009 than in 2008, but Puffins were seen in higher numbers at all sites. The other regularly occurring seabirds showed no overall change.
The highlight off Berry Head was probably a Devon-record count of 145 Balearic and 582 Sooty Shearwaters on 2nd September, with two Yelkouan-type shearwaters seen the same day. Wilson's Storm-petrels were seen off Pendeen, Trevose Head and Strumble Head, while a Madeiran Storm-petrel was seen passing both Pendeen and Trevose Head on 2nd September. As with Yelkouan Shearwater, this species is yet to be officially admitted to the British List, partly due to a combination of identification and taxonomic issues.
The heaviest seabird passage off Whitburn in the North Sea occurred from 13th–16th September, with four-figure counts of Manx Shearwaters, Gannets, Wigeon, Kittiwakes and Guillemots, and three-figure counts of Red-throated Divers, Fulmars, Sooty Shearwaters, Common Scoters, Arctic Skuas, Great Skuas and Puffins. Initial comparison with sites off the southwest UK shows little obvious correlation in the timing of peak movements between the two regions.
Part 4: Marinelife boat-based surveys in the western English Channel
Marinelife surveys in the western English Channel increased in range and intensity in 2009, largely due to additional funding from Natural England and the EU Charm III project, and a new eco-tourism initiative. These effort-based and opportunistic surveys utilised a range of platforms, including ferries and angling charter boats.
Most at-sea Balearic Shearwater sightings involved records of one or two birds, concentrated in coastal areas such as Portland Bill, Lyme Bay and northern France. Many records involved birds scavenging around angling and fishing boats in coastal waters. Again, there is no evidence that land-based monitoring is missing significant offshore movements or aggregations of this species off southern England. An interesting development has been the discovery of very large numbers of Balearic Shearwaters in moulting and foraging aggregations off northern Brittany, involving at least 2000 birds. Further survey work in 2010 and 2011 will better constrain the numbers involved in these aggregations.
Large numbers of auks were noted in Lyme Bay in February 2009, estimated at 16,000 Guillemots and 4000 Razorbills. An unseasonable Great Shearwater was also seen in Lyme Bay in February. Large foraging aggregations involving hundreds of Gannets and Manx Shearwaters were seen in western Lyme Bay in August. Other notable records in the English Channel included single Fea's-type petrel and Wilson's Storm-petrel (within UK waters) in August–September, and a Black-browed Albatross reported by a fisherman off Salcombe (south Devon) on 23rd July (presumably the same as the Gwennap Head bird).
It was deemed to be a poor year for cetaceans and Basking Sharks in the English Channel, partly due to the dominance of unsettled windy weather for much of the summer. Despite this, a total of over 550 cetacean sightings relating to 11 species were made during Marinelife surveys in the region. Harbour Porpoise was the most frequently encountered cetacean, with 260 sightings relating to a maximum of 618 animals. A small wintering population in Lyme Bay was a new and important finding.
There were over 100 Common Dolphin sightings, mostly in deeper water during the early winter and spring periods. Bottlenose Dolphins were also regularly recorded, with 93 widely scattered sightings relating to a maximum of 1540 animals. Largest numbers were seen in summer and autumn, and included two pods of ~100 animals. One individual with a distinctively notched dorsal fin (Cookie) was seen off west Cornwall, south Devon and south Dorset in 2009.
Small numbers of White-beaked Dolphins were again recorded in outer Lyme Bay, with 19 sightings relating to about 170 animals. Most sightings were between early July and late October, although up to 13 were seen in early January. Lyme Bay is the most southerly known regular site in Europe for this cold-water species. Several calves were noted in early August, amongst a group of 35 animals present for several days off Berry Head, feeding on pelagic fish. A total of 20 different animals were photographed, including one in central Lyme Bay in October 2009 that was first photographed 15 km away in August 2007.
Scarcer cetaceans seen during Marinelife surveys in the western English Channel included single Cuvier's Beaked Whale and Northern Bottlenose Whale (which sadly died), and small numbers of Long-finned Pilot Whale, Risso's Dolphin and Striped Dolphin. There were 24 Minke Whale sightings in 2009, but no Fin Whales in a poor year for the species in the Biscay–southwest UK region. Just nine Basking Sharks were seen, and only six Ocean Sunfish.
Marinelife survey work was featured on the BBC One Show in November 2009, and filming for the BBC Coast series was also carried out (showing in autumn 2010).
Part 5: SeaWatch SW project news
SeaWatch SW and SAHOFS hosted the third annual South West Marine Ecosystems (SWME) meeting, held in Plymouth on 14th December 2009. About 40 invited representatives of various science and conservation organisations were in attendance, and provided an overview of environmental conditions and marine wildlife sightings in 2009. The unsettled summer weather again dominated the discussions, in particular its impact on marine megavertebrate occurrence and Portuguese Man-o-War strandings.
SeaWatch SW and Marinelife data continue to contribute to a number of conservation initiatives. Project data have contributed to recent Biodiversity Action Plan and Species Action Plan updates for Basking Shark and Balearic Shearwater, respectively. Project data have also contributed to consultations on offshore renewable energy installations, and a seabird foraging fact sheet on Balearic Shearwater (produced by RSPB).
The SeaWatch SW website accumulated over 30,000 individual hits in the period 2007–09, and news items on sightings during the Gwennap Head survey appeared in local and regional media. A PhD student and several Masters-level project students at University of Southampton are working on SeaWatch SW data, investigating the spatio-temporal controls on marine megavertebrate distribution off the southwest UK. Two new PhD students (Sophia Butler-Cowdry and Lavinia Suberg) will be joining the project team this autumn to further these research activities.
Zooplankton sampling off Gwennap Head in Sept 2009 (Photo: Russell Wynn)
Data being collected by the SeaWatch SW survey team are currently contributing to a number of scientific studies, led by staff and students at the National Oceanography Centre Southampton, in collaboration with colleagues at several UK universities and research organisations. These studies include:
- geolocator tagging and colour-dyeing of Balearic and Manx Shearwaters
- calibration of acoustic and visual monitoring of small cetacean activity around rocky reefs
- land- and boat-based surveys and zooplankton sampling, investigating the importance of topographically controlled tide races to marine fauna and
- the influence of meteorological and oceanographic phenomena on Basking Shark, cetacean and seabird sightings off the southwest UK.
SeaWatch SW is continuing in 2010, with public sightings and effort-based data on Balearic Shearwaters again being collected at a regional and national level. Effort-based surveys of all target species are being carried out at Gwennap Head between 15th July and 15th October, supported by data from several sister sites. A variety of Marinelife boat-based surveys in the western English Channel are also continuing through 2010.
If you feel inspired after reading this report and would like to contribute to SeaWatch SW 2010, please visit the project website and/or contact the project co-ordinator for details of how to get involved. The project website and co-ordinator addresses are shown below.
To get involved in boat-based survey work in the western English Channel with Marinelife, contact Kate Lewis.
Finally, we would like to thank all the individuals and organisations that contributed to SeaWatch SW 2009. Vital financial support was received from Total Foundation, RSPB, BTO, SAHFOS, RNBWS, BirdGuides, The Seabird Group and Marine Information Ltd.