Where and when Guillemot and Razorbill breed on rocky coastlines around Britain and Ireland, but are mainly absent on the English coast from Lincolnshire to Hampshire; Guillemot is much more numerous. Both disperse widely in winter and can be encountered almost anywhere around the coast. Puffin has a more northerly breeding distribution, although there are significant colonies in Wales and Ireland; very small colonies persist along the English Channel. In winter it is markedly pelagic, with few seen from shore except during wrecks. Little Auk is a rare winter visitor, but thousands occasionally occur in late autumn in the North Sea during persistent northerly winds, when some may be blown well inland. Brünnich’s Guillemot is a very rare winter visitor, not annual, mainly to Shetland and n. Scotland; most records relate to tideline corpses, live birds being extremely rare.
Bill When separating Guillemot and Razorbill, pay particular attention to the bill. Guillemot’s is slim and pointed, obvious at some distance, even in flight, giving it a distinctly pointed head/bill profile. Razorbill’s diagnostic oblong bill is readily apparent in flight, giving it a characteristic blunt-headed impression; note, however, that first-winter Razorbill has a much smaller, less blunt bill than the adult, but it is nevertheless obviously short and thick compared to Guillemot (full bill size is not acquired until about three years old). White lines on the bill and face (vertical on bill and horizontal across the top of the lores) are noticeable in summer, even at a distance. In winter, adults basically show only the vertical white bill line (the white loral line is very faint); first-winters lack any white.
Size and structure Guillemot is slightly smaller and slimmer and, on the water, shows a more rounded head than Razorbill. The latter is sturdier and more thickset with a larger, heavier and squarer head. It also has a noticeably long, pointed tail (can be obvious when diving); at rest on the sea, the tail is cocked to give a more ‘banana-like’ shape than Guillemot, which has a shorter tail and a more truncated rear end. Structural differences are not obvious in flight, although Razorbill appears heavier at the front, mainly because of its large bill. Guillemot’s legs trail behind its body whereas Razorbill’s are cloaked by its longer pointed tail. This difference is, however, extremely difficult to discern at any distance.
Plumage Adults summer Guillemot’s upperparts are obviously very brown, whereas Razorbill’s are jet black, this difference easily separating them (providing light conditions are reasonable). Consequently, both the white trailing edge to the secondaries and the white sides to the rump are much more contrasting on Razorbill. Guillemot has variable dark streaking on the flanks, the smarter Razorbill having unmarked pure white flanks. Winter In winter plumage, Razorbill has extensive and solidly black ear-coverts, with a lobe of white extending up behind them, but this is often sullied with grey; thus, Razorbill has a distinctly capped appearance at any distance. Guillemot is much whiter-headed, the result of the dark brown in front of and around the eye curving up strongly behind to produce an extensive area of white on the rear of the head; in addition, a noticeable dark line curves back from the eye, into the white. Both show a partial black collar on the neck-sides, sometimes extending with varying intensity right around the foreneck, most frequently on Guillemot, particularly northern birds (Mather 1991). ‘Northern and Bridled Guillemots’ Guillemots gradually become slightly larger and darker towards the Arctic, such birds looking black in the field and thus more similar to Razorbill. These birds are unlikely to be seen in southern areas. The incidence of ‘bridled’ Guillemots also increases towards the north. In summer plumage these birds have a narrow white eye-ring and a narrow white furrow running back from the eye; they are decidedly uncommon in the south of their range. Juvenile to first-summer Juveniles leave the nest sites before they are fully grown and are cared for at sea by the adults. Guillemots at this age are small, short-billed and fluffier than the adults and lack dark flank streaking; they can usually be detected by their persistent high-pitched begging calls. Juvenile Razorbills are similarly small, and have poorly developed stubby bills, lacking the adults’ white markings. Juveniles of both vary, but Razorbills tend to be darker on the chin and throat, and seem far less vocal. Following a partial post- juvenile moult, both species resemble winter adults, but the bill remains less well developed (see ‘Bill’ above). First-winter Guillemots have the flanks less streaked than the adults and may have a larger area of white on the head-sides. Note that adult Guillemots and Razorbills moult early into summer plumage, so winter-plumaged individuals in late winter and spring are invariably first-winters. Even in their first summer, they may retain white feathering on the chin and throat (as can older individuals); Guillemots also have faded brown wings.
Diving action Note that all species of auk dive with a distinctive open-wing action (but do not use their legs to dive).
Razorbill’s aerial display At their breeding sites, pairs of Razorbills (sometimes singles or trios) often indulge in a distinctive aerial display with slow-motion wingbeats with the wings held in a pronounced ‘V’ (strangely reminiscent of the display of Rock Dove/‘Feral Pigeon’ Columba livia).
Distinctive and well known, but distant individuals in flight, winter adults and young birds may be less easily identified.
Size and structure Its small size is usually apparent (about three-quarters that of Guillemot and Razorbill). In summer, the huge, brightly coloured, triangular bill and white face should be obvious; in winter, the bill is duller and the face greyer. Juveniles have a smaller, less deep and stubbier bill that is predominantly greyish. On the water, it looks stocky and large-headed, with a truncated rear end. Fluorescent orange legs and feet are obvious in summer, but are duller and yellower on juveniles and winter adults.
Flight identification Easily identified in summer, appearing small and stocky with a whitish face and a massive colourful bill, which produces a front-heavy appearance. The bill and face are darker in winter and the bill is smaller on juveniles. The body is otherwise rather stocky with a stubby rear end. Short, rounded wings are slightly angled back from the carpal. The flight action is rapid with rather flappy wingbeats and frequent shifts in body angle. The upperparts are black (like Razorbill) but it lacks Razorbill and Guillemot’s prominent white sides to the rump, as well as their white trailing edge to the secondaries. The underwings are very dark, appearing black, but grey at close range.
Size and structure A tiny auk, only two-thirds the size of a Puffin and half the size of a Razorbill or Guillemot; it is in fact similar in size to a Common Starling Sturnus vulgaris. On the water, it appears small, stubby, horizontal and neckless, with a small but thick black bill that produces a snub-nosed effect; it also has a short, cocked tail. It floats very low on the water, often dragging its wings between dives.
Plumage Most distinctive in winter is a prominent lobe of white extending from the throat up behind the black ear-coverts; also a narrow black half-collar around the neck-sides. It has three or four short white lines across the scapulars, usually visible at some distance. In summer plumage, the chin and throat are black and it has a narrow white half-circle over the eye (the latter sometimes present in winter). First-winters are duller and browner.
Flight identification Very distinctive, appearing small and dumpy – or ‘short and stubby’ – with a stubby bill. It has quite short, pointed, rather swept-back wings and rapid wingbeats. It can look almost wader-like at a distance. Very black and white and clean-looking, the black including the rump and tail. Even in flight, the head pattern is distinctive, with black extending below the eye, a lobe of white up behind the eye and a black half-collar from the upper mantle onto the neck-sides. Like Puffin, it has very dark underwings but, unlike that species, it has a white trailing edge to the secondaries.
A very rare vagrant, which should not be identified unless all of the following differences are clearly established.
Bill Pay particular attention to the length and shape of the bill. It is noticeably thicker and stubbier than Common Guillemot’s with the upper mandible downcurved towards the tip, while the lower mandible may show a slight gonydeal angle halfway along. To quantify this, the distance between the eye and the foremost extension of the feathering on the bill is twice that from the tip of feathering to the tip of the bill (about equal on Common Guillemot). Brünnich’s has a narrow white stripe at the base of the upper mandible (‘tomium stripe’) that is obvious at close range but not at a distance. This can be faint or lacking on some whilst, conversely, some Common Guillemots may also show a suggestion of this feature. Also, beware of the effects of Common Guillemots carrying fish in the bill, especially when observed at a distance.
Size and structure Slightly larger and stockier than Common Guillemot; on cliffs it has a heavy, ‘rugby ball’ shape. On the water, it tends to hold its shorter and stubbier bill slightly more horizontally. It has a steeper forehead, with a stronger forehead peak. The tail is short, like Common Guillemot, but can be persistently cocked. Juvenile Common Guillemots and Razorbills have shorter bills, so particular care is required in late summer and early autumn (although Brünnich’s is very unlikely to occur at this time).
Plumage Darker brown than Common Guillemot, but not as black as Razorbill. It lacks Common’s flank streaking, the clean white flanks appearing much more similar to Razorbill’s. Consequently, in summer it looks cleaner and more ‘black and white’ than Common. From the front, the white of the breast protrudes into the black of the upper neck in a sharper point than on most Common Guillemots. In flight, both the white trailing edge of the wing and the white rump-sides contrast more strongly. In winter, the most important plumage feature is that the dark of the head extends down to include the whole of the ear-coverts, so the black is much more extensive than on either Common Guillemot or Razorbill, forming something of a capped or hooded effect. In addition, on first-winters at least, the whole of the face is dingy grey and there is also a very thick black half-collar on the neck-sides. In consequence, the whole of the head appears darker than on Razorbill or Common Guillemot. Note also that it moults into and out of winter plumage much later than Common Guillemot, so any dark-headed guillemot in late autumn/early winter or any pale-headed guillemot in spring is worth a second look.
References van Duivendijk (2011), Grant (1981), Mather (1991).