Follow our returning birds
Spring is approaching and with it the first migrant birds will cross continents to breed in our woods and fields. But when can we expect to see the season’s first swallow, or hear a cuckoo? Dominic Couzens reveals the great bird migration timetable
The days are lengthening, and with the coming spring comes a great exodus from the countryside, as many of the birds that spend winter in Britain set off for their summer breeding grounds overseas. The musical babbling of geese retreats northwards without fanfare; redwings and fieldfares melt away from our fields and hedgerows, literally gone overnight.
In the Nordic countries, these species are harbingers of spring, so they are going to where they are welcome. But here, their setting off on a spring night is a gentle affair and their quiet preparatory songs seem subdued.
The land has been preparing, though, for new airborne arrivals. Leaves and buds are bursting, invertebrates are multiplying, new flowers appear every day, rolling out white, yellow or blue carpets. Already the resident birds have been in full song for weeks. They have territories and most are already paired. Warm spring weather releases teeming invertebrates to provide most of the new arrivals with plenty to eat. The woods and hedgerows await.
THE RACE TO CLAIM TERRITORY
Once the spring migrants do arrive, they tend to breeze in. The first brave chiffchaff may seem to haunt the willow blossom meekly but
it is a bird on a mission. The pioneers are in a hurry, with just one thing on their minds: they must get settled as soon as possible and establish a territory. So, the first chiffchaff is immediately followed by multi-chiffs, and swallows surge northward, a trickle of flickering wings, then a flurry and finally a surge. The first individuals back have the best chance of getting the choice of territory. An early stake of a good territory is likely to lead to breeding success.
In truth, they have been in a hurry since leaving their winter quarters. The northward spring migration is both a marathon and a sprint, right from the start. On the comparatively relaxed autumn migration, Arctic terns cover about 330km per day; on their spring migration, however, they average 520km a day. Swallows race north at a speed of about 320km a day, with some breaks.
SWELLING WITH SONG
Almost invariably it is the males who arrive first, with females some two weeks behind, because it is the males that sing and the males that settle territorial boundaries. Many individuals sing in transit, practising perhaps. It means that, over the few weeks of songbird invasion, the song swells enormously, so that at times new voices seem to be added every day.
Soon there is hardly a corner of Britain that is unaffected by the happy invasion. The hedgerows resound to the scratchy-record phrases of whitethroats, while blackcaps fill the woodlands with their fuller-throated whistles. Cuckoos add their own sonorous soundtrack to forests, moors and marshes, while in some sacred scrubby woodlands in the south-east of England a few nightingales still hold forth.
“We now know that birds can orientate using the sun, and the rotation around the North Star”
Swifts squeal over cricket grounds, seasons coinciding, nightjars fill the hot night air of midsummer heaths and turtle doves purr from the soporific canopy of tall shrubs on lazy days.
It isn’t only the sounds, of course. Terns splash into sheltered coastal waters and ospreys plunge into northern lakes. House martins dash to and from the eaves of houses, while puffins add their unique vitality to seabird colonies and Arctic skuas add menace to the same, as prolific stealers of fish from hardpressed smaller birds. At times it seems that the arrivals bring the whole ecosystem to life, adding verve and fizz, action and skulduggery.
INSPIRING AWE AND WONDER
It isn’t just the places in our countryside that are enriched by the effervescence of summer migrants – people are, too. The arrival of swallows has lifted hearts for millennia, as it confirms the inevitability of spring, with better times surely following in the fork-tailed bird’s wake, and other birds have done the same in many parts of the world. Our ancestors would have read nature’s calendar, noting the winged arrivals with a delight that must have been profound. People today can still tap into that joy if they take the time outdoors.
These days we can also add awe to our emotions. As bird migration has been studied in more detail, it becomes more of a wonder, not less. We now know that birds can orientate using the sun, as well as the rotation around the North Star. We also know that birds detect magnetic fields and may be able to see them; the angle of incidence of the Earth’s field becomes steeper as you go further north, and birds can probably detect this. All these senses are inside their tiny brains.
Experienced birds remember the location of their territories by sight, returning after six months away. Inexperienced birds have their migration programmed into them, so that birds such as cuckoos can find their way to the forests of the Congo entirely on their own, and back again. They are fuelled by body fat. They arrive in good shape, many fattening up in the West African tropics before a single-leg flight over the Sahara Desert.
These are just some of the marvels of migration. People have always been intrigued by it and now we, knowing more than any previous generation about the phenomenon, are left open-mouthed. To be honest, we should applaud every single bird that arrives, bright and breezy, in the spring.
There is something wonderful about these natural yearly events. The return of migrants in the spring is both magnificent and reassuring. Nature is our outlet in a fearful world and there are few better cures for anxiety than awe and wonder.