WHERE TO SEE THEM
Storm Petrel is best looked for by seawatching in spring and autumn from a westerly headland with onshore gales. They breed largely on islands on the west coast of the UK and on the Northern Isles. foraging. Just recently it has been discovered that Storm Petrels also use their sense of smell to avoid inbreeding. Individuals can recognise family odours and are drawn to those with a different olfactory profile.
The birds also use their sense of smell to recognise their home colonies. The sheer mysterious nature of Storm Petrels, and many other seabirds, too, is reflected in a plethora of recent studies into seabird taxonomy, or classification. Hardly a week goes by nowadays, seemingly, without a new storm petrel, shearwater or albatross being unveiled. Back in the 1980s there were 65 shearwaters and petrels, 14 albatrosses and 21 storm petrels; the figures are now 99, 21 and 27.
Different petrels
The trend is continuing, too, because it now seems that there is a different species of Storm Petrel not far away, a ‘cryptic’ species barely recognisable from our own. While there are ‘British Storm Petrels’ in the Atlantic from the Canary Islands to Iceland, there are also storm petrels in the Mediterranean. Just recently, it has been discovered how different they are.
British Storm Petrels breed in large colonies, and after the nesting season they migrate into the South Atlantic, going as far down as the waters off South Africa. Mediterranean Storm Petrels, however, apparently stay in their eponymous sea all year round. They moult earlier, have different calls, are bigger, blacker and stubbier-billed. And most surprisingly, they have a distinctive diet.
There aren’t any supplies of floating Euphausiid crustacea (‘krill’) in the Med, so the Mediterranean Storm Petrels take more fish. And fascinatingly, it seems that they often catch fish at night by diving underwater, perhaps going down as deep as 5m. They hardly ever do this in the Atlantic – it’s exciting, intriguing stuff.
Over the last few years, another deeply intriguing aspect of Storm Petrel life has also come to light. Since at least the early 1980s it has been shown that playing sound recordings of Storm Petrels at night attracts them to coastal stations, including rocky islands and promontories. It is now known that these are mostly young, pre-breeding birds up to about four years old.
However, in recent years, the plot has thickened. A study of the stomach contents of adults arriving at their nesting holes on islands in the Bay of Biscay came back with baffling results. It found that the second most important food items were isopod crustaceans. No surprise there – except that the species concerned live exclusively in the intertidal zone of beaches.
In Biscay, adults were flying at night over beaches at high tide. It is possible that the birds were using this habitat to replenish their own nutritive needs. One bird caught a fish usually restricted to estuaries.
OVER THE LAST FEW YEARS, ANOTHER DEEPLY INTRIGUING ASPECT OF STORM PETREL LIFE HAS ALSO COME TO LIGHT
Rich pickings
Further studies found even less likely food items, including, of all things, the seeds of plants, and a few insects. A study from Portugal also suggested that Storm Petrels forage over beaches at night during their migration from the Southern Oceans.
There is no doubt that Storm Petrels are largely pelagic and spend most of their time far out at sea. This is their natural habitat and the reason for their success.
Even the beachcombing French birds spend most of their time out of sight of land over moderately deep water. There is little doubt, however, that in summer, at least, individual Storm Petrels in many parts of their range may well routinely venture close to shore, where pickings are rich and condensed, and where hard-working birds can spend some time feeding within reach of the colonies. For many of us who have always known of Storm Petrels as classic oceanic birds, the idea of them creeping towards the shore on summer nights takes some getting used to. But then, the idea of these mites skimming over the sand and mud also seems entirely reasonable.
For such an apparently delicate waif, it’s a snug and perfect fit.