by Mike Dilger
Robins are not the only bird from our chosen twelve to sing for their supper during the winter months, as the British-breeding Nightingales, currently overwintering in west Africa, can also occasionally be heard uttering snatches of song from deep within the Senegambian scrub at this time of year. Unlike in England, where, upon arrival, they will be initially keen to sing both during the day and night, in Africa their performances are usually reserved for just the matinee slots, with the song also tending to be shorter, less complicated and more fragmented. Exactly why the males sing on their wintering grounds is not entirely clear, but there may be a territorial element, or it could just represent the perfect opportunity to practise their bewilderingly complicated song, in preparation for their return back to the breeding grounds. By contrast, all British Cuckoos, currently centred around the Congo River and the surrounding Congolian swamp forests, are thought to make little, if any, noise in their wintering quarters. Rarely even observed in this vast and largely undisturbed habitat, it would seem that quietly moulting and feeding out of sight of the innumerable Congolese predators may well be the best strategy for these highly secretive and mercurial birds.
Also keen on keeping a low profile, any adult Peregrines not actually out hunting at this time of year will be keen to spend as much time as possible conserving energy, which will simply be achieved by discreetly perching out in a sheltered spot. Providing they are able to find enough food to keep their internal furnace fuelled, their freshly moulted feathers should at last be in a position to keep them sufficiently warm irrespective of what the British winter dishes out.
Unlike urban Peregrines, which are able to hunt around the clock in winter, the Puffin’s inability to hunt at night will mean its days during winter will be kept incredibly busy if it is to find enough food to survive in this hostile environment. Using their short, stubby wings to propel them below water, it was widely assumed from the limited data gathered that Puffins routinely dived to substantial depths in pursuit of food. A depth of 68m, for example, was recorded off Newfoundland, with Puffin expert Mike Harris initially estimating average depths to range from 21m to 33m. However, by attaching time-depth recorders to Puffin leg-rings, Harris’s team were subsequently able to gain a much more accurate picture as to both the depth reached and the time the Puffins spent under water. The research revealed that although the Puffins do commonly go down to 35m when pursuing prey, the depth when all dives were combined averaged at only around 4m. What fascinated the researchers, however, was not only how shallow their study birds went, but how often they dived, with the key technique seemingly being ‘little and often’. One bird followed in their study, for example, made 194 dives in just 84 minutes, with an average dive lasting just 28 seconds, which gave just six seconds of recovery time at the surface before submerging once again. Another bird followed made 442 dives in just over two and a half hours, in the process spending 70% of this time underwater. Doubtless, as the days continue to shorten towards the winter solstice, just finding enough to eat could well occupy virtually all their waking hours.
Also confining their hours of feeding to between dawn and dusk, the British Swallows currently overwintering in the Western Cape of South Africa will converge at favoured winter roosts from as far away as 50km as the light begins to fade each day. As Swallows prepare to depart our shores in the autumn, reedbeds are often considered the prime roosting habitat of choice. However, in Africa, in addition to wetland sites, the Swallows will also regularly roost amongst sugar cane, maize and even trees. Some of the best-known sites will be occupied each winter, with certain roosts known to have been used for at least 50 years and possibly containing over a million birds, while others are much smaller and ephemeral by nature. As Swallows begin to arrive at the roost from all points on the compass, initially their technique seems to involve little more than flying around aimlessly, but as the light level drops, presumably below a certain threshold, they will then form tighter flocks as they rapidly wheel over the roost. As the Swallows continue to swirl directly above their accommodation, small groups will then begin to peel away from the main flock before dropping vertically down into the vegetation below. Presumably this method of synchronised flying, as with Puffins approaching dry land early in the breeding season, will make it more difficult for raptors to target and catch individual birds. Taking a while to settle down for the night, there may also be some shifting of position, together with accompanied twittering, as juveniles are shoved out of the best spots by older birds. In spite of realising the benefits of a safety in numbers strategy at night, Swallows are rarely tolerant of close contact with each other and will try to keep a respectable distance wherever possible. Possibly the only time when their personal space is invaded will be on those nights when the weather has turned so cold that communal warmth will trump their naturally frosty attitude.
In the particularly large wintering roosts the majority of birds tend to be juveniles and this proportion will become even higher as the austral summer proceeds, possibly even approaching close to 100% by the time the older birds have started to return to their breeding grounds in the New Year.
As the Swallows seek each other’s company at night, late autumn should also see any established pairs of British Tawny Owls finally roosting closer together again for the first time since the summer. The number of roosting sites will also be narrowed down to a few favoured locations as the temperature continues to fall, and safe in the knowledge that their territory should be fully secured, the pair will finally be able to turn their heads slowly towards the breeding season early next year.
December
Though it’s tempting to ‘hibernate’ indoors during the month of December, a festive walk on the wild side could be rewarded with surprising views of animals, as the short, cold days see them dropping their guard to forage out in the open. Midwinter is certainly not downtime for the Red Fox, for example, as the males will be vocally and actively defending their territories with the mating season just around the corner, and garden bird-feeders across the land will be bustling with business too. Freshly moulted, the tits and finches will be a particularly active presence in virtually any garden, and with most of our summer visitors happily settled in Africa, our resident Robins and Tawny Owls will have scarcely budged all year. Throughout this whole month, the birdlife eking out a living in frosty Britain will have only three things on its mind: keeping well fed, keeping warm and keeping safe.
Early December
Having already moulted their flight feathers by late summer, it could take until early December before adult Tawny Owls will feel sufficiently well equipped to repel the worst excesses of winter and finally replace the last of their body plumage. Tawny Owls are one of very few British species to exhibit more than one colour form or morph, with the majority of birds’ plumage split into one of two categories – either principally brown or mostly grey. Certainly in Britain, the brown colour morph is by far the most common, which contrasts with Finland, where historically grey Tawny Owls have tended to predominate. Plumage colour is believed to be hereditary, with a long-term study of Finnish Tawny Owls finding that not only was the grey colour genetically dominant over its brown counterpart, but in particularly severe winters with thick snow cover, the grey-coloured birds had a higher survival rate. However, the milder winters over the last 28 years in Finland have seen the proportion of brown Tawny Owls increasing from 30% to 50%, a possible case of evolution driven by rapid climate change. With the brown owls seemingly less well adapted to colder conditions, this may indicate why in Britain, with its relatively benign winters, the majority of Tawny Owls will indeed continue to stay tawny.
Quite literally half a world away from the Tawny Owls, it will be months before the British Swallows currently overwintering along South Africa’s Western Cape will see their plumage once again at its brilliant best. Becoming progressively warmer with each passing day as the austral spring takes hold, the average temperatures of around 20°C around Cape Town in early
December should see plenty of flying invertebrates for the Swallows to feed on as they trawl the skies from dawn to dusk. Studies have indicated that the overwintering Swallows tend to forage mostly within 50km of their favoured roost, possibly only changing where they’ll spend the night when food becomes scarce.
Likewise, those Cuckoos encountering good feeding opportunities in the Congo may well be reluctant to undertake any large-scale movements for the rest of the winter. An exception to this largely sedentary rule, however, was provided by Chris the Cuckoo, the only bird to have been successfully tracked for four successive winters by the BTO using satellite technology.
First tagged with a transmitter in Norfolk in June 2011, Chris was subsequently followed for four ‘African tours’ until his sad demise while crossing the Sahara in the summer of 2015. With most Cuckoos safely ensconced in the Congolian swamp forests, during early December in both 2013 and 2014 Chris suddenly upped sticks, before flying 800km further south to Angola. Around twice the size of France or Texas, Angola is bordered to the south by Namibia, with Zambia to the east, the Democratic Republic of Congo to the north-east and the southern Atlantic Ocean to the west. The country has vast mineral and petroleum reserves, but the economy is only just recovering from an intense civil war that lasted until 2002, and which has ensured that Angola still retains one of the worst life expectancy and infant mortality rates in the world. Like the rest of tropical Africa, Angola experiences wet and dry seasons, with a short rainy season between February and April, a dry period between May and October and intermittent rainfall during the winter.
As a proportion of the Cuckoos proceed down to Angola, most British Nightingales are currently assumed to be still holding patterns, and small territories, in the coastal scrub dotted along West Africa’s coast. Experiencing a dry season from November to mid-May, yet with temperatures still likely to be above 20°C, it is highly likely that western Senegal and The Gambia will be coming progressively drier as the month proceeds. The weather in the North Sea and north-east Atlantic Ocean, however, will be a touch more unpredictable for the overwintering Puffins. With these hardy little seabirds currently scattered across a whole range of sea areas, such as Forties and Dogger in the North Sea, to the Faeroes and Southeast Iceland north-west of Britain, and Rockall, Bailey and Shannon to the west, the Puffins will have few opportunities to shelter from any gales or storms which appear with monotonous regularity at this time of year.
Severe weather on the continent will also have a direct impact on the numbers of Bewick’s Swans overwintering in Britain. Any freezing conditions in the Netherlands, for example, where up to 70% of the total population of all Bewick’s Swans in north-west Europe can be held in early winter, will suddenly result in Britain seeing an influx of ‘new’ birds moving away from ice-bound lakes and frozen fields. Capable of making the journey in one short-haul flight, it won’t be long from when the swans are forced out of their Dutch wintering sites to when they begin turning up in British overwintering flocks like WWT Slimbridge in Gloucestershire and WWT Welney in Cambridgeshire. Entering relatively settled flocks with an already established dominance hierarchy may initially result in aggression flaring up once again as the ‘newcomers’ fight for a grudging acceptance from the ‘regulars’. Additionally, being probably unfamiliar with the best feeding and roosting sites means these Dutch birds may well have little choice other than to follow a watching and learning brief until they familiarise themselves with their new surroundings. Likewise, in a good Waxwing year, early December should see the number of Waxwings continuing to swell, as birds that arrived as early as October are joined by recent immigiants pushed across the North Sea as a direct result of a shortage of food in Scandinavia.
Systematically stripping the trees and berries as they merrily go about their nomadic existence, the Waxwings will usually choose to pluck most of the fruit directly from the shrub or tree, but will occasionally also descend to the ground at sites where food may have already ripened and fallen. Each berry is picked with a slight stooping motion and only held briefly in the bill before then being gobbled down following a quick flick back of the head. Being light and acrobatic birds means clinging to the undersides of branches to hoover up any harder-to-reach berries can be achieved with the minimum of fuss, and they will even briefly hover to pluck any fruit suspended from the extremities of the flimsiest twigs. While Hawthorn and Rowan berries are usually swallowed whole, the birds tend to be much fussier when feeding on Cotoneaster and Viburnum. These slightly less palatable berries will be dissected by their tweezer-like bills in order to extricate the seed and pulp, before the skin is then discarded. Any Waxwings feeding on large fruits, such as apples, will then proceed to apply a different technique again, using the bill like a dagger to liberate chunks of pulp. As fruit is rich is sugar, but deficient in a number of other essential prerequisites, such as proteins, these frugivores will need to devour large quantities to garner sufficient nutrients for all their daily functions. The Waxwings cope with large quantities of fruit by having relatively large livers to help metabolise the excess sugar and will also need to drink frequently to counter the dehydrating effects caused by this incredibly specialised diet.
As Kingfishers’ food doesn’t grow on trees, in addition to maintaining an exclusive territory, they will also need a considerable degree of skill and level of luck if they are to catch enough food to see them through the dark days of winter. With only their own bill to feed, they can help their cause by spending long periods quietly perched out of view, thereby ensuring energy expenditure is kept to an absolute minimum. The Kingfisher’s biggest enemy in the winter is prolonged freezing weather, as the formation of a thick layer of ice will instantly make fishing impossible. In very severe winters, many birds will simply abandon their territory for ice-free conditions near to the coast or head even further afield. A small number of Kingfishers ringed in Britain during the breeding season have even been recovered on the continent, with the highest number (three) being recorded from France, where the winter temperatures, certainly in the western half of the country, may well be a touch higher than across large parts of Britain. Whether these birds then return here when conditions finally began to improve is of course anyone’s guess.
Being equally susceptible to freezing conditions and without a winter territory to tie them down, as soon as the temperature slips below zero many British-breeding Lapwings may simply either disappear off to the near continent, or at the very least head to the frost-free estuaries in the south and west of Britain. During intense cold snaps, movements of Lapwings can be quite dramatic, such as the 4,500 observed passing in a south-westerly direction over Tring, Hertfordshire in just 50 minutes on 9 December 1967. Once conditions do improve, however, the flocks are thought to favour a quick return ‘whence they came’, as competition for food in these hard weather refuges may quickly become intense as the birds are forced together in ever larger flocks.
As the days begin to shorten towards the end of the year, the more rural Blue Tits are thought to respond differently to the Lapwings by breaking up their large autumnal flocks into smaller and less mobile groups. In a long-term study of rural Blue Tits overwintering in an oak woodland in Kent, the individual birds seemed to spread themselves out across the wood, and confine their movements to within fairly small and defined areas. These wintering areas were not defended as strongly as individual breeding territories in the spring, but the boundaries seemed nevertheless to have been respected by neighbouring birds. By contrast, many suburban and urban Blue Tits seem to spend the winter roaming more widely than their country cousins as they take in a variety of feeding stations during the course of each day.
Harsh winters will inevitably exact a heavy toll on many of our smaller resident birds, but just like those Blue Tits preferring town to country, any Robin eking out a living alongside us humans will find its chances of survival hugely boosted by capitalising on any food we leave out. Historically happiest either taking food from a bird
table, or cleaning up any scraps dropped by other more acrobatic birds helping themselves from feeders above, it seems that Robins have recently learnt an agility trick or two. A far more common sight in winter gardens these days is that of a Robin darting out of the vegetation to land directly on one of the feeder perches, before then grabbing a sunflower heart and quickly turning on its heels to consume its prize from nearby cover.
Recently voted Britain’s favourite bird, the Robin undoubtedly achieved this spot in large part due to its endearing feature of being uniquely tame. Considered on the continent to be a shy woodland bird, in Britain it seems to revel in human company, leading to one of its commonest monikers, ‘the gardeners’ friend’. It seems the Robin perched on a fork handle is not just a concocted image to sell Christmas cards, but is down to the bird’s genuine confiding nature, which it will use to take advantage of any morsels unearthed as we turn over our herbaceous borders and vegetable patches. It’s believed this opportunistic action has been simply adapted from an ancient behaviour of following Wild Boar, a species which would have been common in prehistoric Britain. Guilty of disturbing the soil as they forage for roots, shoots, invertebrates and carrion, any food missed by the Wild Boar will represent a free meal for a sharp-eyed Robin following in close attendance. As Wild Boar became extirpated towards the end of the Middle Ages, the Robins may have simply looked upon us as little more than tall pigs!