Newsletter Extras - Bird Migration with a Difference (Nov 2014)
Many people are aware that some of the birds that breed in these islands in summer spend the winters far away. Traditionally, the first call of a cuckoo provoked letters to the newspapers and there is the saying that "one swallow doesn't make a summer." We are lucky that the songs of cuckoo, whitethroat and nightingale are still heard across Bookham Common in May and swallows, martins and swifts skim above our rivers, ponds and fields.
However, the summer visitors only tell part of the story of migration. In the south of the country, we may catch glimpses of birds that nest much further north as they pause to rest or refuel on passage in autumn or spring. Ring ouzels (a mountain-nesting blackbird with a white bib) and wheatears are spotted on dry grasslands; waders prod the wetter grass; willow warblers sing in thick cover; ducks and grebes rest on the Thames Valley reservoirs and the occasional osprey stops to fish at Papercourt or Frensham. Then there are those species who find our climate in winter much milder than that of the Arctic tundra where they breed, including redwings and fieldfares (known as "winter thrushes"), bramblings and, among the ducks, shovelers, pochard, wigeon and teal.
There is however another group of migrants that we scarcely notice, whose patterns of movement have only been revealed by the work of bird ringers and detailed research. When the large flocks of chaffinches and bramblings fossick under the fruit trees or beeches, (Wisley RHS's orchards before Christmas are a good place to look), there are far more chaffinches than we see in summer and a disproportionate number of female birds. Why? Because many of the Scandinavian and north European chaffinches spend the winter here, and the females set off earlier and seek warmer places than the males. Indeed, the latin name Fringilla coelebs means "bachelor bird", as it was named across the North Sea. Those who feed garden birds sometimes mention that in recent years blackcaps are staying around all year. In reality, the blackcaps who breed in our gardens, hedgerows and thickets head off south for the winter as they have always done. But some of those who breed in Germany and other places north of the Alps discovered somehow that to the west (much easier than heading south over a mountain range) were some islands where helpful humans provide sustenance throughout the cold weather. So we now enjoy the presence of these warblers, albeit different birds, all the year round and they enjoy our hospitality.
In autumn and winter, the blackbirds, robins, wagtails and starlings seem easier to see. Not only have our resident birds re-emerged into the open after moulting, but they have been joined by many of their continental cousins, fleeing the colder winters. More actual birds, more noticed. While the starling roosts of the Somerset Levels and coastal piers make the headlines, the trees and reed beds of the London parks and open spaces provide warmer roosts overnight and so it is not only the commuters from Stoke D'Abernon station who travel between our villages and the City. Although unlike the humans, the avian commuters earn their food in the suburbs and villages and spend their nights in town. When I worked near London Bridge, at winter dusk out my office window it appeared that someone was emptying sackfuls of starlings into the trees between Southwark Cathedral and the river.
A century ago, when transport used horses (eaters of oats) and farm machinery was less efficient, the cockney sparrows used to disappear from town for a fortnight in August. They weren't off to the seaside, but to the fields around the Home Counties to feast on the spilled grain of the harvest, easier pickings and more nutritious than the spillage from horses' nosebags. While still plentiful in more rural areas, house sparrows are now far fewer in the South East as there is less spilled grain about.
On your garden bird tables in winter, the chatter must sound like that of a major tourist attraction. The blackbirds may have come from Scandinavia, Russia, the low countries or the hedge next door; the greenfinches from Norway or down the road; the siskins from Finland, NW Russia, the Baltic States, Ukraine or Scotland; and others from many parts of the UK, Scandinavia, northern and north-west Europe. The conifer hedges in our gardens and plantings on our commons will hide many more goldcrests, firecrests and coal tits than was the case in high summer as our climate is milder than that of even the nearby continent.
Finally, the ubiquitous wood pigeon is an all-the-year resident, isn't it? Far from it. Those who search the skies looking for visible migration of passing flocks find large groups of woodpigeons among the easiest to spot. Flocks well in excess of 10,000 birds have been reported heading in southerly directions over Surrey in October and November. Birds born and ringed in Surrey have been recovered in various parts of France, as far as Finistère (nearly 500km away). I have seen large flocks heading north over the coast near Chichester in early spring. Other flocks arrive in autumn crossing the coast of East Anglia from the North Sea along with the winter thrushes and other more typical migrants. However, the scientists say that a majority of UK breeding woodpigeon stay in the UK, though even they travel daily between feeding sites in the countryside and woodland roosts.
Pictures courtesy of RSPB (www.rspb.org.uk)