by Mike Dilger
As the Nightingales, Puffins and Cuckoos desert our shores, the double- and even occasionally triple-brooded nature of many Swallows should ensure that many of these industrious hirundines will hang on in Britain for at least another month before they too feel the irresistible pull of the African continent. As the second clutch of Swallow chicks’ demand for food increases exponentially and the female is needed less for brooding this will lead to both parents being suddenly press-ganged into foraging from dawn to dusk. It was of course the famous ‘parson-naturalist’ Gilbert White who wrote in 1789 that ‘all the summer long is the Swallow a most instructive pattern of unwearied industry and affection; for, from morning to night, while there is a family to be supported, she spends the whole day in skimming close to the ground’.
Swallows are exceptionally well adapted for a mode of flight that demands plenty of changes of direction, and when foraging this manoeuvrability is achieved by constantly switching between flapping and gliding. While flapping uses more energy it is of course much faster than gliding and so tends to be used as the main technique. This energetic mode will be interspersed with short gliding periods rarely lasting longer than a couple of seconds. When seen skimming across a field chasing insects, Swallows can give the impression of flying quite quickly, but this is deceptive as their speed is usually clocked at little more than a relatively sedate 8 to 11 metres per second. Their speed will of course vary according to the insects they are pursuing, as fast flight will commonly be needed to catch mobile insects such as horseflies, hoverflies and bluebottles, while a combination of slower flight and gliding will be more than enough to hoover up the weaker flying aphids and midges. Most insects are also caught by the Swallows flying upwards to take them from below, and this is thought to both prevent the insect diving as a means of escape and also to help the bird pick up their quarry more easily against the sky rather than a backdrop of vegetation. Befitting a species that spends a significant part of its life in the air, Swallows have also been calculated as being far more energy efficient than many other birds in flight. Their streamlined shape, relatively long wings and low wing-loading all help reduce the power that the Swallows need to stay airborne. When their long wingspan in relation to the wing area (or high aspect ratio) is also factored in this helps the Swallows to fly slowly without stalling and also when turning to catch insects. These tight turns are also ably assisted by the birds’ fanned tail, which when spread, lowered or twisted can give the vital micro-adjustments considered so crucial as they hone in on their target. Finally, their broad bill will help ensure many more strikes than misses.
After close to four weeks in their fortified chamber, many young Kingfishers from second broods will be ready to fledge by early August. Increasingly cramped in their ever more pungent surroundings, the nesting chamber will be barely fit for purpose by the time the young finally decide to take the one-way ticket down the tunnel and into a world of untold danger. Looking not too dissimilar from their parents, there are a few features that do set the juvenile Kingfishers apart. Overall they tend to be duller in colour, with a dirty wash across their upper chest, have much darker feet and a conspicuous white tip to the bill. It will also be some time before the juveniles have mastered the characteristic shrill whistle so distinctive of the adults, and in the intervening period will have to make do with a ‘chip’ type call which they employ to stay in contact with their parents. Initially they will harass their parents mercilessly to be fed, but it will be only a few days before their parents tire of those antics, forcing the young to either rapidly learn the art of fishing or go hungry. Becoming waterlogged and drowning is a very real threat to the young apprentice Kingfishers as they learn their trade, and they will also need to develop a proficiency in stunning their prey before swallowing in order to ease the fish’s passage down their gullet. Another key life skill will be understanding the importance of keeping their plumage in tip-top condition by regular preening. Like the youngsters of any species, some juveniles will learn faster than others, and in the ‘dog-eat-dog’ world of the Kingfisher it will be the birds that are both keen to learn and take pride in their appearance that will have a much higher probability of surviving through the winter and beyond.
Still very much a family party, the Bewick’s Swan cygnets feeding away in the perpetual daylight of the Arctic Russian tundra will be growing quickly with the arrival of the first days of August. The family will be feeding on sedges, grasses and the berries of plants like Cloudberry, Cowberry and Crowberry, which should all be ripening by now. But while foraging they will still need to be constantly alert to the presence of predators across this flat, unforgiving landscape, particularly as both parents may still be flightless. Despite the long days, the temperature will already have begun to drop, with the closest town of Naryan-Mar, for example, falling from an annual high of around 13.5°C in July to an August average of 10.5°C. Dropping quickly after this shortest of summers the temperature on the swans’ breeding grounds will then probably remain below 0°C for the entire period between October and April, only thawing once the swans return in May.
Also preferring to keep it in the family on the breeding grounds, the adult Waxwings will only just have begun their annual moult, which is likely to continue through to November and possibly even December. The extended nature of this moult means that in all likelihood most of the Waxwings arriving in Britain, from October onwards, will still be actively replacing their feathers on the move.
Also carrying out a partial moult of their body feathers, most of the young Waxwings will still be quite some distance behind any early fledged British Robins which should just be applying the finishing touches to their moult by early August. Shedding their spotty plumage, as the distinctive orange-red spreads from the upper centre of the breast outwards and downwards, the Robins on completion of their first moult should be pretty similar to how their parents looked in the breeding season. Adopting the badge of maturity ahead of the adults who are still in mid-moult will see the young pretenders looking to steal a march on the ‘seniors’ as they set about trying to hold a territory for the very first time.
Those Peregrine Falcons that fledged earlier in the summer will still maintain loose bonds with both their parents and their natal site into August, but as they continue to become ever more independent and explore sites further afield, following their progress becomes more difficult. By now, the flocks of moulting Lapwings will also have become highly mobile as they continue to exploit the best feeding areas either close to their breeding grounds or further afield. Certainly British-breeding Lapwings have some of the least understood migrations, as the population will contain a combination of flocks moving within Britain and also birds migrating either to Ireland or even the continent, leading to a very complex picture. However with a plethora of feeding opportunities, plenty of warm days and the majority of continental Lapwings still to arrive, this will inevitably become a time of intense feeding in preparation for the colder weather to come.
By late summer, many juvenile and adult Blue Tits will have merged to form flocks with possibly dozens of other birds from a variety of species. With the food patchily dispersed, a single Blue Tit could spend much of the day attempting to track down the best feeding sites, but its chances of finding good food supplies will be vastly increased by joining forces. Linking up with Great Tits, Coal Tits, Goldcrests, Wrens and even Treecreepers, as well as Chiffchaffs and Blackcaps before they migrate, the mixed flock can work a circuit of woodland, scrub or rural gardens in the full knowledge there will also be more pairs of eyes on the lookout for danger. The different species frequently travel and feed together with little conflict as they will tend to occupy subtly different niches when foraging. Often losing sight of one another as they each search amongst the foliage, twigs, branches and trunks, they will listen out for the contact calls as the flock moves on; being left behind would make the individual more vulnerable to predation. Feeding with acrobatic dexterity on the outer branches and flimsi
est of twigs should enable the Blue Tits to hopefully find sufficient food while ensuring they don’t either compete with the other species in the foraging flock or become food for Sparrowhawks themselves. The only other species which might compete for the same feeding niche as the Blue Tits, such as Coal Tits and Goldcrests, tend to be either subordinate in the dominance hierarchy, or in the case of the Long-tailed Tits, prefer to keep to their own kind.
Having hatched back in early April, the young Tawny Owls will finally be taking the first tentative steps away from their parents’ territory. Initially they may just roost away, only to come back to the site they know best to hunt, but before long they will will bid farewell to their parents and move out permanently. On departure, it’s thought the youngsters will explore the wider surrounding area as they scout for a location in which to settle permanently. However, extensive ringing, radio telemetry and satellite tracking has shown the juvenile Tawny Owls will rarely move far from home, with the most common distance between where they hatched and ultimately settled only around 4km. By collating all ringing records, the BTO discovered that a mere 7% of young Tawny Owl recoveries were found more than 20km from where they hatched. The record movement of 687km was by a young Tawny Owl ringed in the Scottish Highlands as a chick, only to be later recovered dead in Dyfed, Wales. The likeliest explanation for this extraordinary distance is that the owl must have been accidentally hit by a vehicle, before then becoming trapped until it finally became dislodged in Wales.
Rarely breeding until at least two years old, the best hope for any dispersing juvenile will be to either chance upon a vacant territory, or replace an adult that hasn’t survived the breeding season. For those not lucky enough to immediately strike ‘territory’ gold, there will always be the fall-back position of becoming a non-territorial ‘floating’ bird, in the full knowledge that if they get caught by the resident pair they will be driven out with little mercy!
Mid-August
By the time that British school holidays are well under way, the majority of seabird colonies will already have become Puffin-free zones, as the birds abandon their colonies and head off out to sea. Having bid farewell to terra firma for another year, many will have already begun their annual moult, resulting in a far more muted and drab winter plumage. This new coat – and perhaps this is no coincidence – seems to match the dull, uninspiring colours prevalent in both the North Sea and North Atlantic throughout winter. Perhaps the most noticeable change between the Puffin’s appearance during the breeding season and throughout winter can be seen on its bill, as the bright orange-red sheaths are sloughed off to reveal a far more slimline black and dull-red beak. In addition, the bright red ornaments around the eye are shed, the cheek rosettes at the base of the bill shrink and fade, the feet lose their bright orange coloration and dusky-coloured feathers emerge from the previously pale grey face patches. As the birds take on a far more sombre appearance, the only feathers retained from the breeding season will be those directly responsible for flight, which will not be shed until much later in the year.
Recent research seems to indicate that British-breeding Puffins will disperse widely upon leaving the colony, but thanks to the BTO’s work tracking British-breeding Nightingales with geolocators, it seems they may pass along a far more defined migratory path as they head south through Europe. Data collected from the ground-breaking Nightingale ‘OAD’ indicated that by the middle of August, having initially arrived in France, it then set off in a direction towards the Iberian Peninsula. Following a similar route to the migratory path Nightingales are believed to take when travelling north in spring, it seems that Spain and Portugal are not just exploited for rest and recuperation after crossing the Sahara Desert and the Mediterranean Sea, but also in preparation for tackling them on the southward journey too. Travelling south at a much more sedate pace compared with the race to get to their breeding grounds in spring, by now the British-breeding birds could well be mingling with a much larger contingent of French Nightingales also bound for Africa. Boasting up to a million pairs of Nightingales each summer, the sheer size of the French population illustrates how Britain is, and probably always has been, right on the edge of the species’ natural range.
Having departed Britain well before the Nightingales, it is no surprise that in most years the vast majority of Cuckoos will have already moved south of the Sahara Desert by the middle of this month. For example in the four years between 2011 and 2014 that Chris the Cuckoo was tracked during his southward migration, only in 2014 did he not manage to reach Chad by mid-August. Chris’s late arrival into Africa that year also seemed to have mirrored the progress of many of the other tracked Cuckoos that summer, which were also observed delaying their departure from Europe for reasons unknown.
Land-locked by Libya to the north, Sudan to the east, the Central African Republic to the south, Cameroon and Nigeria to the south-west and Niger to the west, land-locked Chad is Africa’s fifth largest country. Roughly split into three major geographical zones, the northern third of the country comprises desert in the form of the southern Sahara. This arid region then gives way to the Sahelian belt in Chad’s centre, followed by the Eastern Sudanian savanna in the wetter southern third of the country. While the Sahel consists largely of semi-arid steppe dominated by palms and thorny acacia bushes, the higher rainfall in the savanna region creates a far more fertile environment, resulting in a much richer diversity of wildlife. Mostly consisting of large swathes of grassland ideal for grazing, in addition to elephants, rhinoceroses, giraffes, antelopes and many of the large African carnivores, this hugely diverse region has recorded over 500 species of birds and over 1,000 endemic plant species. The Cuckoos are thought to time their arrival in the savanna to coincide with the middle of the region’s wet season, which is brought about by the ‘intertropical front’ operating between May and October. Driving a huge flush of plant growth, the arrival of the rains will also promote an abundance of attendant larvae, such as caterpillars, which theoretically will then be presumably targeted by hungry Cuckoos keen to refuel after such an exhausting flight.
Fledging around the middle of August, the warm temperatures mean there should still be more than enough invertebrate food available for the Swallows’ second broods to catch as they come to terms with the joint tasks of both defying gravity and eating on the wing. From extensive data collected by bird ringers, it does seems that these later broods tend to experience much lower survival rates compared to the first broods fledging earlier in the year. Based on the number of birds returning the following spring, a number of theories have been put forward as to why Swallows that fledge later might have drawn the ‘short straw’. First, the difference in diet between the first and second broods seems to be an important factor. The food available to Swallows of course will vary throughout the year, with an increase in aphids and a decrease in large flies observed as the summer proceeds. As the high nutritional value of large flies makes them far more profitable to hunt, their decline in abundance throughout the summer may mean that any fledged Swallow will have to work harder for the same nutritional return. This is compounded by the fact that in mid-August, the days, and available light for foraging, will be much shorter than in late June. Also for those second and even third clutches reared in the exact same nest-cup as an earlier brood, an increase in the number of blood-sucking mites could also affect the general level of fitness of the chicks. Any small and subtle difference in the juveniles’ health could mean the difference between life and death as the Swallows push their bodies to the limit during the physically stressful and hugely demanding autumn migration.
By the middle of August, the power of flight should finally be returning to the adult Bewick’s Swans as they continue replacing their flight feathers up on their Arctic Russian breeding grounds. For those parents with cygnets, this should enable them to once again step up their level of protection against any marauding predators. Now over a month old, the surviving cygnets should be swiftly replacing their off-
white down for their first full set of feathers. Sporting a dusky grey plumage and a flesh-coloured bill, the young are easily differentiated from the snow-white plumage and characteristic yellow and black bills of their parents for some considerable time. In fact the full adult plumage will not appear until at least their second winter back in Britain, and with a couple of additional years passing before they will even contemplate a first breeding attempt, the swans could easily be at least six or seven years old before they are sufficiently experienced to see their own young successfully through to fledging.
By now freely moving around the taiga forests, the family parties of Waxwings are now believed to start aggregating into larger flocks as they go about their regular routine of feeding and roosting. This flocking not only serves as protection against predators, but is also thought to operate as an informal information exchange, with hungry birds following those well-fed individuals which have patently located good feeding grounds out of the night roost. Not content with just the company of their own species, the Waxwings may also associate at this time with other species which have bred in the forests of northern Europe, such as the Fieldfare. This noisy, gregarious and garrulous member of the thrush family has always remained an incredibly rare breeding species in Britain, with no more than a handful of confirmed records at a few remote sites in Scotland and northern England. However, each winter up to a million birds will cross the North Sea to help themselves to our berry crop, making them a far more abundant and regular visitor to Britain than the erratic Waxwings.