Imagine a bird the size of a sparrow but able to survive for decades on the open ocean, that sounds like a fairy and smells like perfume, that lays an enormous egg but abandons its chick for days on end, and lives in perpetual summer by following the sun from northern to southern hemisphere and back every year.
This might sound like the stuff of fairy tales, but these are real birds called Storm-petrels (or “stomies” for short) and are the subject of A Rocha’s longest-running marine research project, based from Cruzinha in southern Portugal, where the birds can be found in early summer during their annual migration journey. The original aim was simply to discover if non-breeders could be attracted to the coast away from any breeding colonies, but with a tally of over 6,000 stormies, they now work in partnership with Cardiff University to investigate responses to climate change in migration patterns.
The European Storm-petrel is the smallest of Europe’s ocean-going birds, yet one of the most magical and mysterious. Weighing on average 25 g (no more than a large box of matches), it spends its life out at sea, only coming to land to breed in rocky crevices on remote islands. Even then it is rarely seen, as it only leaves the nest at night to avoid aerial predators such as gulls and falcons.
A boat trip can offer a better chance to see these birds as Storm-petrels often feed behind fishing trawlers. They flutter just above the water; their legs dangling into the water (the name “petrel” refers to St Peter walking on water), picking off live or parts of fish, crustaceans and other small marine organisms.
The annual migration of the European Storm-petrel is impressive; these tiny birds travel from their nest sites in the North Atlantic, to spend the northern winters at sea in the Atlantic Ocean off southern Africa, with some individuals even rounding the Cape into the Indian Ocean. On these migration journeys they can cover speeds of 200 km per day (125 miles). Who knows what distance must be clocked up in its typical lifespan of thirty years or so!
As the Storm-petrels return northwards towards their breeding grounds on north Atlantic islands, they wander along the coasts of Africa and Europe checking out potential breeding territories. It is some of these birds that hear and are attracted to the sound of birds of their own kind, calling unexpectedly from the base of a cliff on the south coast of Portugal. Here, a small team from Cruzinha is camped for the night in this impressive natural setting, huddled around thermos flasks, rather deafened by the amplified sounds of the petrels’ songs, and peering through the gloom at the arrangement of mist nets around them. It does not help that “stormies” are mostly black apart from their gleaming white rump!
Over the many years of this A Rocha study, which began in 1990, more than six thousand petrels have been caught in this way, studied and released again into the night. A remarkable proportion (about 8%) have already been ringed elsewhere. It is exciting fieldwork and a unique scientific opportunity to study the petrels away from their breeding grounds and to better understand how these tiny birds are designed to live an oceanic life. Currently, the research is now led by Drs Renata Medeiros and Rob Thomas of Cardiff University, together with Marcial Felgueiras and Gui Réthoré of the A Rocha Portugal Field Study Centre, we are examining their behaviour, ecology and the links between climate, oceanography, marine food-webs and the diet and migration strategies of the Storm-petrels.
To do this involves a rather bizarre mixture of traditional natural history (sitting out all night at the bottom of a cliff hoping the birds fly into our net) and hi-tech “sciency stuff”. Each bird is weighed, measured and a lightweight numbered ring fitted to one leg. A single breast feather is taken, which provides a tiny DNA sample, from which we can determine the bird’s gender (this is needed as males and females look identical) and overall breeding area. We also get ridiculously excited if the bird produces some faeces, as this can be collected and used to investigate the bird’s diet and feeding behaviour using some clever methods pioneered at Cardiff University and developed by Renata during her PhD research.
Back in the lab, Renata extracted DNA from the squishy faeces samples. Some of this DNA comes from the bird itself, but some of the DNA comes from the prey animals that the bird has eaten. By sequencing this DNA (“reading” the genetic code using various methods), Renata could identify the species of prey that each bird has eaten. By linking this information about diet to year-to-year changes in sea temperature, plankton productivity and the birds’ energy levels during migration, we are building an increasingly detailed picture of how climate change is affecting marine ecosystems –from the tiny plankton and fish, to the migratory seabirds that feed on them.
The study is topical, and more than a little rewarding to have close such encounters with these wonderful little beings. Each year, we welcome volunteers from all around the world and of all ages, to take part in this exciting research project. Small teams of 6-8 volunteers stay for 10 days each, working alongside with scientists from Cardiff University and A Rocha Portugal. No previous experience is necessary, just enthusiasm and a reasonable level of physical fitness; all necessary training is provided.
You can find out more about past years (2006-2014) by visiting our blog: http://stormies-online.blogspot.co.uk/ or more current news by finding us on Facebook: Storm Petrels in Portugal and if you would like to find out more about our wider stormies research projects at Cardiff University, follow us on Twitter: @CUStormies.
‘We get ridiculously excited if the bird produces faeces, which we collect to investigate diet and feeding behaviour.’ Rob taking a precious sample. (Andrew Shepherd)