Cory's Shearwater Calonectris diomedea
Computer-generated image © Colin R Casey.
Still a great county rarity, with fewer than ten records up to 2022. The first flew south at Saltfleetby-Theddlethorpe Dunes NNR in Aug 1985; the next two in 1988 and 1995 were also on very similar dates in August. One went north close in at Gibraltar Point in August 2000 and it wasn't until 2009 that another was picked up during a seawatch at Witham Mouth in September; it drifted slowly north past Freiston Shore and away up the west side of The Wash, briefly landing on the sea. Singles were seen in 2011 and 2012 and then a 10 year gap until July 2022. The extraordinary events of 2023 are summarised below.
The mini-invasion of Cory's Shearwaters in 2023
The year 2023 was easily the best year ever for this vagrant (to Lincolnshire) shearwater. This was not entirely unexpected given the tens of thousands which were logged off the SW headlands in Aug-Sep. The first was seen Aug 17th at Chapel Point, with another individual Aug 18th which was sequentially logged at several sites headed north, and then going back south as follows: north at Chapel Point and Wolla Bank 07.14hr; Anderby Creek, 07.27hr; Sutton on Sea, 07.38hr. Then south at Anderby Marsh at 08.09hr; Chapel Point 08.13 hr; Gibraltar Point 08.41-08.43 hr.
The action wasn’t over as more were seen Sep 17th: singles north at 07.16hr. and 10.24hr at Gibraltar Point, and later three north together at 16.50hr. At Anderby Creek two flew north in the morning (09.09h and 10.17h) and another two went north together in the evening (17.39h). It seems likely that fewer than half a dozen birds were involved in these movements, with sightings duoplicated along the coast at the usual well-watched sites. Several blurry but recognisable photographs were taken to mark this seabird event.
The rarity of this species in the county is most likely related to geography with no peninsulas or prominent headlands. For example, the species is regularly recorded in small numbers Yorkshire coast, usually heading south and with occasional larger influxes, one of which occurred in 2001 with 41 records. Although good numbers of Sooty Shearwaters, Ardenna grisea, were seen off the Lincolnshire coast on that date, no Cory’s Shearwaters were reported. There are well known late-summer movements in the South-western approaches, with occasional huge influxes such as the 17,250 recorded in 1980 including an astonishing 10,940 past Cape Clear Island, Co. Cork on August 16th. Unsurprisingly with such huge numbers arriving in some years, the species ceased to be considered by BBRC in 1983.
| Site | First date | Last date | Count | Notes |
| Saltfleetby-Theddlethorpe NNR | 14/08/1985 | - | 1 | |
| Huttoft Bank | 20/08/1988 | - | 1 | Flew north |
| Skegness | 22/08/1995 | - | 1 | Flew north |
| Gibraltar Point NNR | 30/08/2000 | - | 1 | North close in, 18.56-19.01. |
| Witham Mouth | 13/09/2009 | - | 1 | Drifted slowly north, on the sea at one point |
| Trusthorpe | 10/10/2011 | - | 1 | Flew south |
| Gibraltar Point NNR | 24/09/2012 | - | 1 | South, from seawatch ridge 13.45h. |
| Wolla Bank | 08/07/2022 | - | 1 | Flew north during a sea watch |
| Chapel Observatory | 17/08/2023 | - | 1 | |
| Chapel Observatory | 18/08/2023 | - | 1 | Flew north at 07.05hr, then south at 08.13hr, |
| Wolla Bank | 18/08/2023 | - | 1 | Flew north at 07.14hr. |
| Anderby | 18/08/2023 | - | 1 | Flew north at 07.27hr, then south at 08.09hr. |
| Sutton on Sea | 18/08/2023 | - | 1 | Flew north at 07.38hr. |
| Gibraltar Point | 18/08/2023 | - | 1 | Flew south at 08.41hr. |
| Gibraltar Point | 17/09/2023 | - | 5 | Flew north at 07.16hr (1),10.24hr (1), and 16.50hr (3) |
| Anderby | 17/09/2023 | - | 4 | Flew north at 09.09hr, 10.17hr and 17.39hr (2). |
| Chapel Observatory | 17/09/2023 | - | 1 | Flew north |
Finder's Report: Cory's Shearwater at Saltfleetby, August 14th, 1985, first county record.
by Michael Tarrant and Barry Clarkson.
The late afternoon of the 14th was sunny, with a light on-shore south-easterly wind; conditions not particularly favourable for a heavy sea-passage, but the easterly component to the wind direction was promising. We arrived at the tide-edge at about 1700 hours and immediately noticed a northward movement of Fulmars with an occasional Gannet flying south. Some 45 minutes later, with only 4 Arctic Skuas, 2 Great Skuas and 46 Fulmars in the notebook, we had resigned ourselves to another uneventful sea-watch.
Looking northwards, MJT saw an approaching bird some 150m distant, gliding in the manner of a shearwater on bowed wings, close to the surface of the sea . As it drew closer, it became clear that it was a large shearwater, but when it flapped its wings with four deep, slow strokes and the medium-brown upperwing and white underwing were clearly seen, it gave the initial impression of an immature Herring Gull. Although there were no other birds in the immediate vicinity for size comparison, it appeared to be longer than Fulmar but not as stocky as Herring Gull. By now, BMC had been alerted, and we both mentally took notes as the bird sheared across our field of view: these are the points we noted.
Flight action: Low over the waves mainly on bowed wings, occasionally flapping (4 beats) in the light breeze. The flaps were deep and slow. When gliding, the wings were held so that the hand was angled back and curved down at the wrist.
Size and structure: Slightly larger and less compact than FuImar. Head large, giving bull-necked impression. Forehead steep rounding to flat crown. Full-girthed from breast to belly, vent tapering markedly to long undertail coverts. Tail very short and rounded. The wings were broad-based, long, and slightly rounded at the primary tips.
Head and bare parts: Forehead and crown, down to just below the eye, greyish . The dark eye was centrally placed within the face. The bill was pale yellow, long and stout along its entire length. Leg colour not determined. Nape greyish-brown extending on to sides of neck and down the sides of breast. The grey-brown colouring reached below the edge of the open wing.
Underparts: Chin to undertail coverts, white. Tail brown. The details of the underwing were not fully noted in the field but as the shearwater banked and moved further out, and the chance of a close photograph was missed, but one was taken, albeit a poor one and at some distance. We realised then that we had obtained virtually no detail of the underwing, but fortunately later scrutiny of the transparency revealed that the white underwing showed a narrow , dark leading and trailing edge, with primary tips broader and an indistinct dusky line from carpal through the coverts.
Upperparts and wings: Back to rump greyish-brown. Uppertail coverts were distally one-third white forming a horseshoe band, contrasting sharply with the tail but becoming progressively indistinct towards the rump. Upperwing, scapulars darker than the rest of the wing. Coverts, grey-brown broadly edged grey-buff. Secondaries and primaries brown. The fore-edge of the wing was darker than the rest of the coverts.
At the tide-edge, we determined that the bird was a Cory's Shearwater Calonectris diomedea* having experience of the species in Mallorca in 1981 , but we wished to verify our deduction with the aid of the photograph and available literature to determine any possible confusion species. The only other large shearwater with a pale bill is the Streaked Shearwater Calonectris leucomelas occurring in the NW Pacific, and whose diagnostic features are a white face with streaked hind crown and nape (Harrison 1983). This is the first county record of this species.
*Taxonomic note: since the time of this sighting Cory's Shearwater is now Calonectris borealis, having been split from the closely related Scopoli's Shearwater, now C. diomedea, the large shearwater breeding in the Mediterranean.
References
Harrison P. (1983). SEABIRDS: an identification guide. Croom Helm Ltd; A.H. & A. W. Reed Ltd.
Tarrant, M. and Clarkson, B. (undated) Cory’s Shearwater at Saltfleetby, August 14th 1985. Lincolnshire Bird Report 1985 p.65.
Wallace D.I.M. and Bourne, W.R.P. (1981) Seabird movements along the east coast of England. British Birds 74: 417-426.
(Account as per new Birds of Lincolnshire (2021), included September 2022; updated August 2023)