Leach's Storm-Petrels pushed past Machrihanish on a westerly gale

Thirty-two Leach's Storm-Petrels passed Machrihanish on the 17th, counted from the seawatching point at Uisaed.¹ Few people on this coast ever see one. The bird lives its whole year on the open Atlantic, and the only thing that brings it within sight of the mainland is weather. The Met Office forecast for these inshore waters had westerly winds building to gale force through the 16th and 17th, and a westerly blow is exactly what pushes these birds in against the Kintyre headlands. Uisaed Point has a long record of them on days like this. On the same watch the observer logged 177 gannets and 28 Manx shearwaters moving past.¹

Leach's Storm-Petrel (Hydrobates leucorhous) is a sooty-brown seabird about the size of a starling in the body but long in the wing, with a wingspan near half a metre. The wings are angled sharply at the wrist, the tail is forked, and the white rump patch is usually split down the middle by a thin dark line. The flight is the surest mark at distance: low over the water, bounding and jinking, with sudden changes of direction, closer to a bat or a nighthawk than to anything else that passes this coast. The European Storm-Petrel also comes through here and is easy to confuse at range. It is smaller, with a square tail, a clean solid white rump, and a fluttering, swallow-like flight that skims the surface rather than bounds over it.

At sea the bird feeds on the wing. It hovers and patters its feet on the surface, picking up small fish, squid and plankton without ever settling to dive. It finds food by smell across open ocean, which is how a bird this small makes a living hundreds of miles from land.

The nearest colonies to Kintyre are the Western Isles, chiefly St Kilda, some 200 kilometres to the northwest, with smaller numbers on the Flannan Isles and North Rona. St Kilda alone holds around nine tenths of the British and Irish breeding population. The birds nest in burrows and come and go only in darkness. Each pair raises a single chick, and that chick fattens to nearly twice its fledging weight before it leaves the burrow in late September. Mid-September gales therefore catch the year's young on their first flights over the sea, along with adults leaving the colonies. Those are the birds that turn up off headlands like this one, and in a hard enough blow some end up stranded on beaches or carried inland.

The IUCN rates the species Vulnerable worldwide, and in Great Britain it sits on the Red list.² Surveys on St Kilda found the colony there fell by 68 percent between 2000 and 2019, with predation by great skuas identified as one likely cause.² The 32 that went past Machrihanish came from that stock, blown within reach of a pair of binoculars for one day before the wind eased.