PETRELS & SHEARWATERS Procellariidae

119 species (8 vagrant)

Fairly small to fairly large pelagic seabirds, coming to land only at breeding colonies and even then the great majority do so only under cover of darkness. Only Northern Fulmar readily seen in inshore waters in all weather, but most come close inshore at times, especially in windy conditions. Petrels and shearwaters, together with albatrosses and storm-petrels, are known as ‘tubenoses’ because of their tubular nostrils positioned along the ridge of the bill (i.e. culmen). All are similar in basic shape, with long, narrow, pointed wings and shortish tails. They are masters of the marine environment, spending much of their lives on the wing. In average conditions, flight consists of a series of rapid wingbeats on stiffly held wings followed by long glides and shallow banking turns with wings typically held slightly bowed downwards.

In windy weather, they ride the air currents above the waves, following the contours of the sea surface, making few, if any, wingbeats and banking and gliding on stiffly held wings (a process known as ‘shearwatering’), rearing up 10–20 m or more above the water at times (at which point they are often tilted right over on their sides). Food chiefly small fish, cephalopods and crustaceans; also offal and carrion. 

Feed by shallow plunge-diving, by diving from surface or while sitting on surface; some (especially Pterodroma petrels) also while pattering on surface in flight. Colonial breeders; those nesting in our region choose holes and crevices, or open ledges (Northern Fulmar). Often form large ‘rafts’ at sea when roosting or feeding. Clumsy on land, able only to shuffle along owing to rear positioning of legs. When rising from water they initially patter along surface. Typically silent away from breeding colonies (with exception of Northern Fulmar).

Sexes similar. No seasonal variation. Juveniles and immatures resemble adults. Several species polymorphic, occurring in both light and dark morphs. Complete post-breeding moult commences shortly after (or even during) nesting and finishes during autumn or winter. Post-juvenile moult is complete, commencing shortly after fledging and finishing during autumn or winter. Immatures have complete moult over much the same period as adults. Most likely to be confused with gulls (especially immature gulls) and skuas at longer distances. Both the latter will rear up high (turned over on their sides) and bank and glide for some time and give a ‘shearwatering’ impression, but their looser, less stiff wingbeats and more flexed-back wings when gliding differentiate them even at long range. The smallest shearwaters with their rapid wingbeats can look quite auk-like at times, but auks fly with almost whirring wingbeats on wings that appear too small for their plump bodies. In most cases small shearwaters in rapidly flapping flight eventually bank and glide, revealing their true nature. Points to concentrate on when identifying petrels and shearwaters are: 

Upperpart pattern • Head pattern and bill colour • Underwing pattern • Basic structure • Flight action

Although flight action is a useful aid to identification, it can be difficult to assess objectively unless the observer has considerable experience of several species. It is affected both by wind speed and by the type of activity in which the bird is involved (e.g. feeding, travelling). Moult and abrasion can affect appearance of upperwing in particular, and the wide range of lighting conditions at sea can enhance or subdue certain plumage features. These factors should be constantly borne in mind when identifying shearwaters and petrels. Other species of petrels and shearwaters could well be recorded as vagrants from our region in future, so observers faced with such a possibility should consult Seabirds: an identification guide (Harrison 1985).