by Mike Dilger
Able to feed themselves almost immediately upon leaving their burrows, the juvenile Puffins are certainly quicker learners than the Tawny Owls which, despite having clambered out of their nest as long ago as early May, will only now begin hunting their own food in earnest. Whether the young birds are pushed or jump towards self-sufficiency is unclear, but the motivation may well be a combination of the parents slowly withdrawing their ‘meals on wings’ service as the youngsters themselves steadily take matters into their own hands. Either way, as the incessant begging gradually declines the young will probably only be tolerated for a couple more weeks in their parents’ territory, before it’s made perfectly clear that they’ll need to take their chances elsewhere.
Still totally reliant on their parents, the Bewick’s Swan cygnets will require a further six weeks before the ability to take to the air should see their chances of survival boosted substantially. Until then, the perennial twin threats of predation and poor weather will continue to exact a heavy toll, and the number of chicks in most broods will continue to decline throughout the month. Even for the most experienced parents, to have any more than two cygnets still alive at this stage of the breeding season must be considered little short of exceptional. Like many birds, adult Bewick’s carry out a complete moult every year, but as the swans will need to replace the key flight feathers as quickly as possible before their autumn migration, this will necessitate a period of flightlessness often lasting around three weeks. Obviously during this period of intense moulting, not only are the adults themselves more vulnerable to predation, but they will also be far less able to protect their young. Incredibly, to counter this disadvantage, any pairs still with cygnets are able to stagger their moults. With the female thought to moult first, this ingenious mechanism will mean at least one parent is fully winged for longer, which will in turn give the pair a higher probability of being able to successfully defend their cygnets. On the breeding grounds, the last feathers to be replaced before migration will be those belonging to the tail. The body moult, by contrast, will proceed at a much more leisurely rate, meaning that many body feathers are still actively being replaced well after the swans have arrived in their winter quarters.
For those Bewick’s Swan pairs either unsuccessful or simply unwilling to breed, a moult will also have to be completed, but being unencumbered by young means there will be no need to stagger their flightlessness. As holding a territory will also have become an unnecessary luxury for these birds, many will tend to form large moulting flocks away from the tundra and in the comparative safety of shallow sea bays and coastal regions. Carefully chosen to limit the access of a variety of terrestrial predators, these locations will still need to provide plenty of aquatic vegetation for the swans to feed on. Moulting flocks might not be the choice of all the swans without young, however, as some will prefer to remain on the tundra during this vulnerable period. Without the water as a protective barrier, these swans will instead choose to either hide or break into a surprisingly fast run should they spot any predators on the horizon!
In the taiga forests to the south of the Arctic tundra those Waxwings that successfully bred should by now have formed into family parties as the newly fledged youngsters join their parents on foraging missions. Any element of territoriality which existed around the nest will have disappeared the instant the youngsters fledge, as the families roam the forests for food, often over a far wider area than on their wintering grounds. As the short breeding season draws to a close and darkness at night begins to reappear, the dropping temperatures will also see the individual family members begin roosting together to conserve heat. Staying as part of a family unit during this period will also provide the birds with more pairs of eyes to keep a lookout for Sparrowhawks and Merlins, two predators specialising in hunting small, unwary and inexperienced birds. Any excited or alarmed Waxwings that may have spotted potential trouble will quickly adopt an erect posture, with crest raised, to ensure that the other birds in the party are also aware of any imminent danger.
Due to the longer summer encountered back in temperate Britain, those pairs of Kingfishers opting for another brood will see their second clutch of chicks growing quickly as the month draws to a close. Due to the chicks’ size there will be little opportunity for the parents to turn around in the crowded nesting chamber, resulting in them having to reverse out of the tunnel after the delivery of yet another meal. When the chicks were young the adults would take great care in gently placing the fish down their throats to ensure they didn’t choke. However with their offspring approaching fledging, feeding visits for the parents will consist of little more than a trudge down a slimy tunnel, followed by a slam-dunk down one of the youngster’s throats and a reversal back out into the fresh air. At two to three weeks old, the chicks often line up side by side, with their bills pointing towards the tunnel as they await another delivery from their hardworking parents.
By the time that the second brood approaches fledging, those juveniles still going strong from the earlier brood should already have begun to undergo their first moult. Unlike their parents, currently undergoing a total refit, the juveniles will only replace the head and body plumage during their first year, with most of the flight and tail feathers usually being retained until the following spring. This partial moult will see the youngsters ditching their initially dull plumage as they begin to take on the hues and tones of their parents. However, they will still not be able to pass off as fully mature just yet, as their legs won’t develop the characteristic orange-red adult coloration until the following spring.
Bringing up the rear, many Swallows’ second broods should finally be hatching as July draws to a close. Following the pattern of the first brood, the removal of the eggshells will often be one of the first indications that the young have begun to hatch, and as the female broods the chicks for the first few days the male will once more have to step up to the plate. Upon hatching, the parents will suddenly take the protection of the nest to a whole new level. Any other Swallows caught close to the nest during this time will be subjected to a barrage of alarm calls and predators like cats or rats will be actively mobbed and even struck if they attempt to interfere with the newly-hatched brood.
For both the young Blue Tits and first brood of Robins, late July should see the continuation of their partial moult, as they slowly embrace the plumage and badges of maturity. Any surviving Blue Tit should by now be in the process of gaining the distinctive white face and bright blue cap, while the spotty brown breast of the fledgling Robin will be making way for the famous orange-red breast which it will use for acquiring and holding a territory in just a few weeks. The adults of both species will also be actively moulting, and much of their time will be taken up by finding the extra food to fuel the ‘gas-guzzling’ replacement of feathers, while still keen to remain largely out of sight. The data analysed from thousands of ringing reports reveals that adult Blue Tits are much heavier at this time of year than during the breeding season, doubtless due to the combination of a far lighter workload without chicks to feed and the relative abundance of food. Certainly for adult Robins, the need to keep a low profile, and the resulting lack of territorial behaviour, will mean that July and possibly early August may well be the only time during the entire year that the British countryside will be devoid of the Robin’s song.
Heard here for close to 11 months of the year, the prolific nature of the Robin’s song could not be contrasted more sharply with that of the Nightingale, which will have scarcely uttered a syllable for well over a month now. Needing also to complete a much faster moult than our resident birds will mean that by late July many adult Nightingales will look as though they’ve just been freshly laundered, as they prepare to leave England for Africa. This period before departure is also believed to coincide with a change in the Nightingales’ eating habits, as a largely protein-based diet is replaced by one favouring a higher proportion of carbohydrate. As invertebrate prey becomes steadily more difficult to find, the Nightingales will th
en switch to the abundant amount of fruit suddenly available, blackberries and elderberries being the perfect energy-rich foods with a long, tiring flight just around the corner.
Having already departed our shores well in advance of the Nightingales, the BTO has discovered that late July or early August seems to be the prime time when many British Cuckoos will leave any established stopover locations in Spain or Italy for their journey to the heart of Africa. Followed with the help of satellite technology between spring 2011 and the summer of 2015, three out of four of Chris the Cuckoo’s southerly migrations have him recorded leaving Italy in the second half of July, only to arrive in Africa a few days later. In 2011, for example, a signal from Chris’s transmitter reported him to be close to the River Po in northern Italy on 22 July, only then to be picked up in northern Chad, a distance of over 2,600km away, just 55 hours later! As they power over both the Mediterranean Sea and most of the Sahara Desert in one gigantic hop, it now seems likely that Chad may well be a favoured stopover for many of the British-breeding Cuckoos in July and August. As the Cuckoos generally seem to take a more easterly route on their southward migration compared to their journeys north in spring, this would seem to indicate that many of the birds must pass directly over Libya. With a good number touching down in desertified northern Chad, it seems this arid part of the country may in fact be little more than an opportunity to draw breath before the Cuckoos then quickly move to more fertile regions further south. The richer feeding grounds surrounding Lake Chad in the south of the country represent an excellent opportunity to recover any condition lost while crossing North Africa, and mean the Cuckoos are in no hurry to leave this region until they ultimately head for the tropical forests later in the autumn.
As the summer rolls on, any young Peregrines which fledged in the spring should by now have become sleeker, faster and far more adroit at catching their own food. Having served their apprenticeship well, the loosening of the ties with their parents will probably have been initiated by the young who now be regularly feeding well away from the nest site during the day. Still returning to the comfort blanket of their parents’ territory at night, these day trips will not just be helping the young birds to find other good feeding areas, but also locate possible overwintering locations and even potential breeding territories. At those sites with an absence of breeding Peregrines, birds may well now begin turning up again at a whole host of sites that have been abandoned since late winter as the whole population becomes far less territorial and much more mobile.
Mobility will also have become a distinguishing feature in the behaviour of both British-breeding Lapwings and any immigrant birds still pouring over from the continent. Ringing records of Lapwings which were known to have bred elsewhere, before then being noted in Britain, seem to suggest that the largest influxes originate from Belgium, the Netherlands, Denmark, Germany, Sweden and Norway, but there have also been some interesting recoveries from elsewhere. In 2003, for example, a Lapwing found dead on Romney Marsh in Kent was revealed to have been ringed as a nestling in northern Lithuania in 1994, a distance of 1,724km from where it was recorded. This record is one of a handful of Lapwings known to have originated from a broad arc encompassing Estonia to the north and Poland further south, and due to the very limited number of birds ringed in these countries, these records may merely represent the tip of an iceberg. All these countries surrounding the Baltic sea have much colder continental winters than Britain, where freezing temperatures are the norm, and due to the Lapwing’s inability to extricate food from frozen ground it’s perhaps no surprise that a healthy number will move west to the Gulf Stream-warmed climate found in and around the UK.
August
Synonymous with school holidays and filled with the frenzied activity of families trying to enjoy what remains of the British summer, August is a time when the wildlife will be keen to complete breeding cycles before the nights start drawing in. With the bird breeding season largely over for another year, those visiting just for the summer will either have already departed or be busily stocking up on last minute provisions for the flight. Amongst those birds residing here all year, a continued moult and dispersal into the countryside will be the order of the day, giving the garden that empty feeling of a stadium just after a match has been played. Around our coasts the picture could not be more different, however, as waders like Knot, Turnstone and Sanderling exchange their Arctic breeding grounds in their droves for our mudflats - representing just the vanguard of a whole variety of bird species keen to spend the winter in Britain.
Early August
A mere three months after arriving in England, and with their main flight feathers freshly grown, by August many Nightingales will have already turned their attentions towards the continent, as the exodus takes place to southern Europe and beyond. The sum total of knowledge as to exactly when Nightingales leave Britain was, until very recently, compiled from little more than a combination of the occasional bird recorded at a host of southern English migratory hotspots and a paltry total of 13 British-ringed birds recovered from abroad. However, since the BTO has managed to attach tiny geolocators to Nightingales, the movements of this mysterious bird are now finally being revealed.
Of all the Nightingales with geolocators attached in the spring of 2009 and then crucially re-trapped to recover the equipment the following spring, only one individual was able to deliver any meaningful data. The bird, named OAD because of the letters on its device, is believed to have divulged more information in a single stroke about the movements of Nightingales than in a hundred years of ringing. The recovered data revealed that OAD was thought to have left England in early August, only then to be recorded passing west of Paris a week later. Despite a substantial layover in Spain and Portugal, the spring migration north is now believed to be conducted at a much more rapid rate than the southward journey, which appears decidedly far more leisurely by comparison. Needing neither to proclaim a breeding territory nor a mate in Africa, it seems there may not be quite the imperative for the Nightingales to migrate so quickly, thereby leaving them free to feed along the way.
Unlike the Nightingales which will have certainly moulted their flight feathers in Britain, the adult Cuckoos will only undergo the majority of their annual moult upon arrival at their long-term wintering destination. In fact moulting studies of a variety of different migratory species have shown a general pattern appearing; the further south the birds migrate, the more their moult will be delayed until later in the year.
It is only since the BTO began satellite tracking Cuckoos that the region surrounding Lake Chad was revealed to be a favoured stopover location for many of the British-breeding Cuckoos. Due to its particularly shallow nature, with the deepest recorded point being little more than ten metres, the lake’s size doesn’t just vary throughout the year, but has alternately shrunk and grown enormously over the centuries. Being an ‘endorheic’ system, or a closed drainage basin, means the lake retains the water as there is no outflow or discharge into rivers or oceans, so its precise level tends to be dictated by the difference between any inflow and the amount escaping by evaporation. This will in turn be controlled by the prevailing climatic conditions. The lake is also situated in a region called the Sahel, a climatic zone of semi-arid habitat which runs in a narrow horizontal band across the entire African continent. Representing the transition between the Sahara Desert to the north and the wooded savanna and tropical forests further south, it is likely that this region will represent the first proper opportunity for the Cuckoos to feed since their departure from southern Europe. Using this region to slowly recuperate and recover condition after crossing the world’s greatest desert, the satellite telemetry indicates that the Cuckoos will be in no great hurry to reach the Congo Basin with many staying put until around the time that autumn begins to take hold in Britain.
The plumage of the now fully-fledged Cuckoos still back in Britain can vary enormously between being predominantly grey, to decidedly rufous, with the la
tter coloration not dissimilar to the rare rufous or hepatic colour form of a select few adult females. These juvenile body feathers will not last long though, with many being slowly replaced soon after leaving their hosts’ nests. The exception to this rule will be the the wing and tail feathers, which like the adults’ plumage will not be replaced until much later in the year. While their errant biological parents rest and recuperate in the Sahel, very little is known about the movements of the juvenile Cuckoos, but it is suspected they may well stay in Britain until at least September. Until then, the young Cuckoos will continue to feed themselves on a diverse array of invertebrate food, with large hairy caterpillars probably the preferred food source. As the summer rolls on, a different suite of butterfly and moth caterpillars will in turn become available for the juvenile Cuckoos to exploit, as they hop around the ground, amongst hedges and up in trees for surely one of the most unpalatable of all meals.
At Puffin colonies around the British Isles, those birds which successfully managed to negotiate their young through to fledging will already have deserted the breeding grounds in their droves by early August, with an exodus rather than a gradual withdrawal being the chosen method of departure at most sites. This will give many well-known puffinries a slightly worn-out and unloved appearance as they become deprived of these colourful and characterful birds for another year. In most seasons breeding success will be dictated by food availability, with between 60 and 80% of pairs managing to see their Puffling successfully fledge in those years with abundant Sandeel stocks. The predation level of chicks tends to be highest at those sites with smaller, less densely packed colonies of Puffins and where the safety in numbers strategy is less effective. Additionally, the synchronised emergence of hordes of young at the larger, crowded puffinries will be more effective at swamping the relatively few predators hoping to make a meal out of a defenceless fledgling.