Nightingales in November (66 page)

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.