Identification Guide

The identification of seabirds and other marine animals likely to be recorded during the SeaWatch SW survey is covered by a number of field guides and websites, as listed below. However, at the bottom of the page we provide specific identification tips for the two key target species, the Balearic Shearwater and the Basking Shark, as well as some of the rarer seabirds that may be seen from Gwennap Head.

General seabird and sea mammal identification

Books
The following books are probably the best all-round field guides covering seabird and sea mammal identification in UK and European waters:

• Collins Bird Guide (Mullarney, Svensson, Zetterstrom and Grant) Collins.
• Flight Identification of European Seabirds (Blomdahl, Breife and Holmström) Helm.
• Whales, Dolphins and Seals (Shirihai and Jarrett) A&C Black.
• Whales, Dolphins and Porpoises (Carwardine and Camm) Dorling Kindersley.

Websites
http://www.biscay-dolphin.org.uk/birds.html
Basic ID guide to seabirds of the western English Channel and Bay of Biscay (note that Balearic Shearwater is referred to as ‘Mediterranean’ Shearwater). The site also has a guide to cetacean ID. 

http://www.terra.es/personal5/arbmor/arbsf019.htm
Spanish site with several photos of Balearic Shearwaters taken in the western Mediterranean, and comparison with Yelkouan Shearwater (confusingly referred to as ‘Mediterranean’ Shearwater!).

http://www.seawatching.net/
Excellent site for anyone interested in seabirds and sea mammals, has lots of useful photos. Focuses on the Macaronesian Islands but useful for anyone in Europe. Includes photos of Manx Shearwater and many rarer European seabirds.

http://www.seawatching.net/reports/Catalonia/index.html
Specific link from the above site to a trip report off NE Spain - includes good photos of both Balearic and Yelkouan Shearwaters.

http://www.oceanwanderers.com/
General site on seabirds with identification articles and many photos.

http://www.birdguides.com/webzine/article.asp?a=558
Birguides article (subscriber only) on identification of Yelkouan Shearwater.

http://www.birdguides.com/webzine/article.asp?a=595
Birguides article (subscriber only) on identification of Scopoli’s Shearwater.

http://www.surfbirds.com/searchimages.html
Surfbirds photo gallery search page. Type in 'Balearic Shearwater' for two nice images taken off Scilly.

Balearic Shearwater identification

Balearic Shearwater identification is not always straightforward, and therefore should only be attempted by those with previous seabird observation experience (particularly Manx and Sooty Shearwater).

Size and structure
Balearic Shearwater is slightly longer-bodied and longer-winged than Manx Shearwater, but is markedly smaller than Sooty Shearwater. However, gauging size on lone birds can be difficult. The dimensions of the three species are shown below:

• Manx: Length = 30-35 cm. Wingspan = 71-83 cm
• Balearic: Length = 34-39 cm. Wingspan = 78-90 cm
• Sooty: Length = 40-50 cm. Wingspan = 93-106 cm  

In flight, Balearic Shearwater appears bulkier, longer-necked and shorter-tailed than Manx Shearwater, and often looks slightly pot-bellied with the centre of gravity located just behind the wings. The overall impression is of a less compact and streamlined bird than Manx Shearwater. The feet clearly project beyond the end of the tail (unlike Manx Shearwater), but good views are required to see this feature. Sooty Shearwater is a more athletic bird than Balearic Shearwater, with longer, thinner and more pointed wings, and a cigar- or spool-shaped body. It is worth remembering that Balearic Shearwater is a dominantly inshore species, which undergoes a much shorter migration than either Manx or Sooty Shearwater; this partially explains why the latter two species look more streamlined and athletic in flight.

Balearic Shearwaters with Herring Gulls (Devon, July 2006). Note the size compared to Herring Gull, and the relatively long head and neck. The wings are relatively broad and rounded compared to Manx and Sooty Shearwater.
Balearic Shearwater at Gwennap Head in July 2006 (left) and Sooty Shearwater (right). Sooty Shearwaters are entirely dark chocolate-brown, but show a clean silvery-white centre to the underwing. The belly is always dark, whereas Balearic Shearwater almost always shows a pale belly. The body of Sooty Shearwater is cigar- or spool-shaped and the wings are slender and pointed; the overall appearance is of a more athletic bird than Balearic Shearwater, which tends to show a pot-bellied appearance.

Plumage
The plumage of Balearic Shearwater is quite variable, with some pale birds resembling Manx Shearwater but others appearing as dark as Sooty Shearwater. Typical birds are dull brown above and pale brownish-white below, the brownish tone resembling dark hot chocolate. The palest areas are the belly and centre of the underwing. The vent and undertail is mostly dark brown, and the axillaries and secondary underwing coverts are also dusky brown. Sooty Shearwater is entirely dark brown (blackish in poor light) with a paler, more silvery underwing. Dark Balearic Shearwaters may be confused with Sooty Shearwater but normally still show a pale belly. Manx Shearwater is a more contrasting black-and-white bird, and shows white flanks and rump sides and a white half-collar extending up behind the dark ear coverts.

The plumage tones of Balearic Shearwater are quite variable; this bird is typical with dark brown upperparts
and paler underwings and a whitish throat and breast. Note the dark undertail. Photo taken in Dorset in July 2006.

Moult
Many Balearic Shearwaters seen in UK waters in summer and autumn are at least one year old and are therefore undergoing moult. These birds often appear relatively pale milky brown on the upperparts due to sun-bleaching (especially in bright conditions), and have a patchy appearance. The margins of the hindwing may have indentations resulting from missing primaries and secondaries. Newly-moulted birds or fresh juveniles look much darker and neater.

Balearic Shearwaters photographed from Gwennap Head in late July (left) and early September (right). The July bird is in active moult and shows paler, patchy upperparts and several missing primaries; it is at least one year old. The September bird is darker and neater overall, and is probably a fresh juvenile.

Flight action
Balearic Shearwaters have slightly looser and more ‘fluttery’ wingbeats than either Manx or Sooty Shearwater, again contributing to the less athletic appearance. Both Balearic and Sooty Shearwater have longer wings than Manx Shearwater, and so are more inclined to show swept-back wings in strong winds. Manx Shearwater has rapid compact wingbeats, while those of Sooty Shearwater are quite shallow but always look smooth and effortless, like a well-oiled machine.

Video of a Balearic Shearwater in flight (slow motion). The stiff-winged flight is typical of small shearwaters,
but on Balearic Shearwater the wingbeats are slightly looser and more flexible than Manx Shearwater. Video: Michael O’Keefe.

Both Sooty Shearwater (above) and Balearic Shearwater have a tendency to show swept-back wings when flying into a strong headwind;
Manx Shearwater has shorter wings and is less likely to do this. Note the well-proportioned elongate oval body of the
Sooty Shearwater shown above, and the longer tail than Balearic Shearwater.

Behaviour
Balearic Shearwater is usually an inshore species, and on days with a stiff headwind birds often pass closer to shore than either Manx or Sooty Shearwaters. Balearic Shearwaters are less likely to be found in large flocks when on passage in UK waters, with groups of 1-3 birds typical and very occasional double-figure flocks. Manx Shearwaters can be seen passing singly or in small groups, but flocks of 10-100 birds are more common. Sooty Shearwaters are usually seen as singles. Balearic Shearwaters often form large feeding and roosting flocks in areas where food is abundant; such flocks may hold in excess of 100 birds. Birds actively plunge-dive in pursuit of small shoaling fish, but can also be found following trawlers for fish discards. Odd vagrants are often mobbed by gulls.

Balearic Shearwaters often follow trawlers and scavenge on discards. This brings them into conflict with gulls,
which have a tendency to mob lone individuals. Photo taken in Devon in July 2006.

Yelkouan Shearwater
There have been a number of claims of Yelkouan Shearwater in UK waters in recent years. However, more photo-based research into the variations of plumage, structure and moult of Manx, Balearic and Yelkouan Shearwaters is required before definitive identification criteria are established. It is hoped that careful analysis of birds seen during SeaWatch SW will contribute to our knowledge of these shearwaters, and images taken from Gwennap Head will be added to the Gallery page as the project progresses. For further identification information see the following article, and the websites listed above:

Gutiérrez, R. (2004) Identification of Yelkouan, Balearic and Manx Shearwaters. Birding World, 17 (3), 111-122.

Basking Shark identification

The Basking Shark is the second largest fish species in the world, and can grow to a length of 11 m and a weight of 7 tonnes. Most shore-based sightings of this species relate to a dark triangular dorsal fin and pointed tail moving leisurely along the coast at or near the sea surface. However, from a high vantage point in sunny weather it may be possible to look down upon the body of the animal, which can appear brown, grey or black depending on light conditions. The snout is pointed and the stocky body is broadest at the head (especially when the mouth is open while feeding) and tapers towards the tail. The bright white insides of the cavernous mouth and the long gill slits may be seen on feeding animals, and the large pectoral fins may be visible from above. The dorsal fin is asymmetrical when viewed side-on; the front end sweeps upwards at a roughly 45^o angle while the rear end is steeper and, in some cases, almost vertical. The narrow pointed tail tip is angled backwards at a slightly shallower angle to the front of the dorsal fin. The snout of the animal can sometimes be seen above the surface. Basking Sharks can be seen singly or in groups of up to several hundred animals.

These images show a typical shore-based view of a Basking Shark in sunny weather. Note the erect dorsal fin, the white inside to the open mouth (indicating feeding), the large head and tapering body, and the elongated tail fin.
This view of a Basking Shark from above again shows the white insides to the open mouth
Some Basking Sharks lift the snout above the water surface while feeding, as can be seen here. Length can be estimated by doubling the distance between the dorsal and tail fins.

Other sharks are rarely seen from land in UK waters, of these the Blue and Porbeagle Sharks are most likely to be seen. Both species appear paler then Basking Shark and are a different shape; the Blue Shark is long and slender with a long uppertail, while the Porbeagle is oval-shaped. Neither species grows much beyond 2-3 m in length.

Images of Basking Sharks taken from Gwennap Head can be found on the Gallery page.

Recent articles on rare seabirds in southwest England

The following recent articles are particularly useful for those interested in finding rare seabirds, as they refer to observations of Fea’s Petrels and Wilson’s Storm-petrels off the Isles of Scilly:

• Fisher, A. and Flood, B. (2006) Fea’s Petrel off Scilly: new to Britain. British Birds, 99 (8), 394-400.
• Fisher, A. and Flood, B. (2001) The Fea’s Petrel off the Isles of Scilly. Birding World, 14, 289-292.
• Flood, B. (2003) Wilson’s Petrels off the Isles of Scilly 2000-2002. Birding World, 16 (5), 210-218.
• Flood, B. and Fisher, A. (2005) Wilson’s Petrels off the Isles of Scilly: a five year analysis, 2000-2004. Birding World, 18 (6), 247-249.
• Flood, B. and Lascelles, B. (2004) Another Fea’s Petrel off Scilly. Birding World, 17 (9), 392.
• Lees, A. (2006) Fea’s Petrel in the Western Approaches. British Birds, 99 (8), 401, 403.
• Steele, J. (2006) From the Rarities Committee’s Files: Do we know what British ‘soft-plumaged petrels’ are? British Birds, 99 (8), 404-419.

For back issues of British Birds see http://www.birdingworld.co.uk/BackIssues.htm

For back issues of Birding World see http://www.britishbirds.co.uk/

Wilson’s Storm-petrel (left) and Fea’s Petrel (right). Small numbers of both species have been recorded from southwest UK waters in recent years.