25 August 2015 by Paul Stancliffe
From his expert perch at the British Trust for Ornithology, Paul Stancliffe explains what to look for as the UK’s birdlife migrates in the autumn…
There is a sense of urgency in the bird world during the autumn months, as those birds that only spend the summer here – birds such as the swallows, martins, flycatchers and warblers – head south for warmer climes, and those that breed further north (mostly wildfowl, but also thrushes, finches and buntings) make their way here for the winter.
History of migration studies
Migration studies have been carried out for many years, but were revolutionised just over a hundred years ago with the introduction of lightweight, uniquely numbered metal rings that could be fitted to a bird’s leg. From the tiny goldcrest to the mute swan, birds have been ringed by trained and licensed ringers ever since. As more and more birds were ringed, their movements began to unfold. Swallows didn’t spend the winter months hiding in the mud at the bottom of ponds, as was once widely believed; they swapped the cold northern winter for a South African summer, flying 10,000 miles between the two. During the summer months, barnacle geese don’t turn into goose barnacles, the bivalve mollusc that is the scourge of many a long-distance sailor – they make their way to Svalbard and Greenland to raise their young on the Arctic tundra.
It seems silly now that we believed such tales, but there was very little evidence to suggest otherwise. At the end of summer, swallows were last seen flying over lakes and ponds, taking advantage of the last of the season’s insects that also gather over the water at that time of the year; it didn’t take much of a leap to believe that they then plunged into the water, seeking the relative warmth of the muddy bottom.
Migration studies today
Things have come a long way. We now know where most of our migrants come from and go to. We also know the routes that some of them take, and we understand many of the mechanisms that enable a tiny goldcrest to navigate across the vast North Sea and back again each autumn.
Using a small amount of magnetically sensitive material in the brain, migrant birds are able to tell which way north is. The ability to detect polarised light gives them the position of the sun on cloudy days, and remembering visual clues on their journeys helps to ensure that they get to where they are going with a surprising degree of accuracy. But one of the biggest developments for scientists who study bird migration has been the advancement seen in tracking technology.
In 2011, scientists at the British Trust for Ornithology fitted five cuckoos with satellite tags with the aim of filling in the gaps in the knowledge of the migrations of this rapidly declining bird. The results have been spectacular and we are now able to follow cuckoos as they make their way south. At the time of writing, three birds have just crossed the Sahara Desert, always a tense moment as the crossing is extremely hazardous. The birds can be hit by sandstorms, vicious crosswinds and some of the highest temperatures experienced anywhere on Earth.
Where to see migrating birds
Migrating birds can be seen almost anywhere, but coastal watch points, such as Spurn Point, East Yorkshire, Portland Bill and Hengistbury Head, Dorset, and many of the headlands that jut out into the sea, are among the best places to observe this natural phenomenon. Seeing geese on migration, or just flying from roosting sites to feeding sites, can be quite spectacular, and can be enjoyed at many places across the UK. Barnacle geese can be seen arriving at Caerlaverock, Dumfrieshire, in September – the time when greylag geese are turning up on the east coast of Scotland; pink-footed geese are seen crossing the Pennines, from west to east; while white-fronted geese are arriving in Ireland.
If you are out and about this autumn, keep an eye on the sky for flocks of birds moving overhead and consider how amazing these relatively small creatures are. You can even follow the satellite-tagged cuckoos.
Swallow: Tommy Holden/BTO, Barnacle Goose: Jill Pakenham/BTO, Goldcrest: John Harding/BTO, Cuckoo: Steve Ashton
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