Nightingales in November (5 page)

Dr Chris Hewson, the lead researcher, has said that ‘we have learnt more from this one bird – OAD – than in the previous 100 years of ringing Nightingales!' The upshot of all this cutting-edge technology is that we now believe that most of the Nightingales which come to breed in England will be in the West African countries of Sierra Leone, Guinea or Guinea-Bissau come early January. The BTO has also led the way in the satellite tracking of Cuckoos in recent years, which is finally revealing the mystery of where British breeding Cuckoos go when they leave our shores. Transmitters attached to birds, which are then tracked by satellites, have recently been miniaturised to such an extent that they can now be placed on birds as light as a Cuckoo. Unlike the geolocators, which need the individual birds to be recaptured to retrieve the data, for the last four years Cuckoos have been tracked along both their migration route and into their wintering grounds in real time.

With just one previous record of a British-ringed Cuckoo recovered south of the Sahara, in Cameroon in (believe it or not) 1930, the satellite data is finally uncovering what was one of our great ornithological mysteries. Fifty-four Cuckoos have been tagged over the duration of the project, but only one individual managed to survive the research project's first three years with its ‘on-board' transmitter functioning properly throughout. Chris the Cuckoo, named after the TV naturalist Chris Packham, before the bird's untimely demise in 2015 successfully navigated the perils of the Sahara Desert seven times, collecting ground-breaking data every step of the way! The information collected from Chris, and other male Cuckoos (as the females are still considered too light to carry the current model of transmitters), has so far
uncovered quite a number of revelations. Come the turn of the year it seems most of the British-breeding Cuckoos are still firmly settled in one of two wintering quarters, either the swamp forests of the Republic of Congo, close to the border with the ‘other bigger Congo', the Democratic Republic of Congo, or further south in the altogether more arid habitat of northern Angola.

Remarkably the Cuckoos are still not the most southerly of our twelve birds, with British Swallows having flown down to winter some 2,800km even further south. For centuries, after Barn Swallows disappeared from Britain in the autumn, they were believed to spend the winter in rock or tree crevices, or even buried in mud. It was not until the early nineteenth century that observations of birds over the English Channel, in the Mediterranean and off West Africa, supported the alternative, and at the time controversial, view that they migrated. Only in 1912 was definitive confirmation of the British Swallows' winter home produced, when a female Swallow ringed in Staffordshire by a James Masefield in May 1911 was recovered in Natal on 23 December 1912.

From the BTO's ringing records, it seems that most British Barn Swallows winter in South Africa, with a large number of records predominating from the Western Cape Province, an astonishing distance of around 9,600km from south-east England. Roosting by night in reedbeds or other wetland vegetation, sunrises in early January, representing high summer in the Western Cape, will see the Swallows leaving in waves to fan across the South African countryside to feed. In Britain, the airspace around cattle and horses is often a productive feeding ground as their dung attracts insects and the livestock also flush invertebrates from the vegetation as they walk. In South Africa, herds of game may well offer similar feeding opportunities. A British Swallow
swooping to catch a dung fly from beneath an elephant's legs?… not as far-fetched as it sounds!

Our final iconic bird, the Puffin, may well be somewhat more difficult to track down in early January. Having left their breeding colonies by mid-August at the latest, current research by Mike Harris and his team working on the Isle of May, Firth of Forth, eastern Scotland suggests that most of their Puffins immediately move out into the North Sea. Using geolocators attached to the Puffins, the team found that after then flying around north Scotland to spend the autumn and early winter in the north-east Atlantic, many will have already returned to the North Sea by the turn of the year. Recoveries of Puffins from colonies elsewhere in Britain suggest they disperse widely, with recoveries of birds seeing them turn up from Brittany in France to the Canaries, and a few adventurous juveniles even making it as far as Newfoundland and Greenland.

Mid-January

With Bewick's Swans firmly settled on their wintering grounds for more than a couple of months, and dominance hierarchies mostly established, aggressive encounters between birds should now be far fewer than earlier in winter. Top of the ‘pecking order' will be the families, consisting of a pair of experienced adults and their juveniles which were successfully raised during the previous breeding season. Sticking close together at all times, a family of two adults and three offspring represents a formidable fighting force that is easily able to bully those swans with fewer allies away from the best feeding locations and roosting sites.

Nowhere is this hierarchy more noticeable than at the WWT Slimbridge reserve in Gloucestershire. With the swans fed daily by the wardens, the families will use their superior numbers to barge their way to the front of the queue, and help themselves to far more than their fair share of the grain being handed out. Aware of the fact that numbers equate to dominance, yearlings (swans experiencing their second winter), will often rejoin their parents on the wintering grounds to boost both their own social position and that of their parents within the flock. Any trios consisting of parents and a yearling, although often not able to compete with larger families, will still be able to exert influence over those pairs of swans without any young at all to back them up. Below the established pairs without any young, and even lower down the pecking order, are those adults that have either lost a mate or have been unsuccessful in managing to secure one. And finally, the birds that will struggle the most during feeding and roosting will be those yearlings battling the unfortunate combination of a solitary existence and huge inexperience.

Compared to the highly strung Bewick's Swans, there generally seems far less aggression amongst the socially gregarious Waxwings. By mid-January in a good ‘Waxwing winter', the overwintering population may by now have fanned right across the southern part of the UK, with some hungry birds even braving a second sea crossing to sample the delights of Ireland's berries. Staying in flocks is initially an asset to Waxwings, as it enables them to use their numbers to dominate prime feeding positions, in the process keeping territorial Mistle Thrushes, for example, away from the berries. However, as the fruit resource becomes far more depleted at this time of year, any larger flocks may well be forced to break up into smaller, nomadic groups. These
compact, mobile flocks will then need to range far and wide to ensure they can find enough food to see them through those nights when the temperature dips below zero.

For many of our resident birds that have chosen to stay at home rather than taking a long winter break in warmer climes, extended cold periods can present a very real and imminent threat to their survival. Both Kingfisher and Lapwing from our chosen twelve will struggle to find enough food if the water and soil surface stay frozen for any length of time. According to the BTO, as many as four out of every five Kingfishers that fledge won't see even their first birthday, with a large proportion perishing during periods of severe weather. Struggling to find unoccupied riverine territories, many young birds are pushed in the autumn to spend the winter at the coast to feed in estuaries or even in the sea itself. Although these habitats will rarely, if ever, freeze, the feeding around the coast will always be far more demanding than, say, a quiet chalk stream in Hampshire.

In very harsh conditions, some Kingfishers holding inland territories may be forced to temporarily move if their established feeding areas freeze over. The cold weather movements of continental Kingfishers are well known, and particularly in Germany, where the Kingfisher's name ‘Eisvögel' translates into ‘ice bird'. Perhaps a technically more accurate name, although undeniably more of a mouthful, would be ‘the bird that moves ahead of the ice'!