by Mike Dilger
At this stage the chicks are thought to only know when food is imminent by their parents’ contact calls and possibly by the shadow cast as the male approaches the rim of the nest with food. Even at a very tender age, the Swallow chicks’ gape is a prominent red-orange in colour and is surrounded by a paler yellow flange. Many birds see in ultraviolet light and as the lighter border reflects a different part of the spectrum to the gape itself, this helps guide their parents into the ‘feeding zone’ in the dim light, much like the landing lights on an airport runway at night.
Having laid well before the vast majority of Swallows, the Puffins’ single egg will only now be finally entering the last stages of its six week incubation. Taking three or four days to chip its way out of the egg there will almost certainly be an element of communication between parents and chick as it attempts to break out, with the message from inside the egg being ‘Get ready to start feeding me’ coming through loud and clear!
Bringing up the rear in the mating stakes, early June should finally see summer belatedly arriving for those intending to breed at higher latitudes. Exactly when Waxwings and Bewick’s Swans begin to lay their clutches will depend on how cold the previous winter was and the exact timing of spring’s arrival in the frozen north. In an average year early June should see the Waxwings putting the final touches to their nest, while the male continues to feed his mate to ensure she will be fit and able to lay. Due to their much longer incubation time, the Bewick’s Swans can’t afford to waste a moment, and so those pairs that have successfully secured a territory should already be actively laying by now. The exact position of the swan’s nest is considered crucial, and with no option of rearing their brood anywhere other than on the ground in this barren landscape, an experienced pair will, wherever possible, choose a raised, south-facing hummock or mound. Slightly elevated nests tend to serve the swans best as they give a good all-round view, enabling the pair to track the movements of predators across the tundra, and those locations with a south-facing aspect will also become ice-free quicker.
Once the spot is chosen, the mound is built by simply piling up vegetation from the immediate surroundings, so by the time they’re finished the nest may extend over a metre across and reach a height of up to 50cm. Looking like a doughnut, the central area – which will hold the precious clutch – is then lined with a mix of softer grasses and any down the birds might have going spare. With a good territory so vital for breeding success, many experienced birds will not only return to occupy the same location, but even reuse the exact same nest from previous seasons, after any necessary running repairs have been carried out, that is. Immediately after laying, the eggs are white in colour, but then stain to a brownish-yellow after a few days, and while not quite up to the size of the huge eggs laid by Mute Swans, each Bewick’s egg will still top the scales at around an impressive 280g. Clutch size will not only vary across the tundra according to the age and experience of the pair but also from year to year, however nests of between three and five eggs seem most common. Once laid, incubation will begin immediately and with both parents doing their utmost to protect the clutch from both predators and the worst the weather can throw at them, they will hope to see their cygnets for the first time in just under a month.
Mid-June
The sight of Puffins bringing fish ashore will surely mean just one thing – the chicks, or ‘pufflings’, have begun to hatch. Finally, after an incubation of around 41 days, which will have included three or four days of hard labour as the chick breaks free, the bedraggled puffling will emerge into the dark underground world that will represent its entire universe until it heads out to sea later in the summer. Another sign that pufflings have begun to hatch left, right and centre will be the sudden accumulation of remnant eggshells at the various burrow entrances, signifying completion of the first step in a life that, if all goes according to plan, could last over 30 years.
After drying off, the chick will resemble a charcoal-coloured powder puff, with lilac-coloured feet and a black stubby bill tipped with the white egg tooth, which might stay attached for a couple of weeks. For the first week after hatching, the chick is unable to maintain its body temperature and so would quickly chill and die without being brooded continuously by one of its parents. Rarely needing to eat on hatching day as it finishes off the last of the egg nutriment inside its body, it will quickly develop a keen appetite as the first food items are transferred carefully from the parent’s bill to the chick’s ready gape. Like most chicks on a rapid weight gain course, the puffling will initially spend large parts of the day sleeping, only becoming more animated once a little older.
The young Puffin’s diet consists of pretty much the same food as their parents, with typical prey being a combination of Sandeels, Sprats, small Herring and young stages of fish (gadoids) in the Cod family, such as Whiting and Haddock. Of all the prey brought in, by far the most frequently caught and important item will be Sandeel, with most Puffins in British waters catching the Lesser Sandeel. These small and silvery-coloured eel-like fish have long fins, a forked tail, protruding lower jaws, and are very familiar to anyone who has watched adult Puffins returning with bills full of them during the height of the breeding season. The timing of their life cycle can vary around Britain, but certainly populations surrounding the Shetland Isles tend to spawn in December and January. The eggs then stick to sand grains on the seabed until hatching, when the larvae become pelagic and float around with the zooplankton, until ultimately transforming into the small recognisable Sandeels by May or June. As their name suggests, Sandeels spend much of their life buried in the sand, but in the summer occur as large shoals in the water column when feeding on plankton during the day, before returning at dusk to spend the night tucked up in the sandy seabed. Usually found in waters at depths between a few metres and 70m, this annual harvest is easily within diving range of any foraging Puffin with a hungry chick to feed back on dry land.
Another chick pushing its ‘parents’ to the limits by mid-June will be the Cuckoo. By now much larger than its foster parents, this huge size difference doesn’t seem to prevent the chick’s industrious hosts from realising anything is wrong as they continue to stuff the youngster with food from dawn to dusk. Quite often in order to ensure the food reaches its required destination, the host adults may even need to stand on the Cuckoo chick’s back in order to reach its gape, and the nests of Reed Warblers and Meadow Pipits soon look manifestly unfit for purpose as the chick grows out of house and adopted home. Feathering up quickly, the Cuckoo chick will by now be quickly developing the characteristic white feathers on the back of its head and on spotting its ‘parents’ approaching with food, the distinctive hissing call can be heard from quite some distance. Upon arrival of the food, the bird seals the deal with a demonstrative begging gape and quivering of wings.
Despite eating enough for four or five, the young Cuckoo will actually take longer to fledge than the chicks of most of the host species it parasitises. Certainly in Britain, Reed Warbler and Meadow Pipit chicks will leave the nest after around 12 to 14 days and be dependent on their parents for only a further 12 days afterwards. This contrasts with the Cuckoo needing anywhere between 17 and 20 days in the nest, and still reliant on its hosts for almost as long again, before its departure finally relieves the burden from its beleaguered foster parents. After leaving the nest, the young Cuckoo will usually seek the safety of nearby bushes, where it will then continue to noisily beg for food. Looking rather like an adult Cuckoo at this stage, the fledgling will usually tend to be a touch more rufous in colour and with heavy chestnut barring on its upperparts. It also pays for the greedy youngster at this stage to remain initially largely hidden and perched in one place, as its silhouette in flight will frequently illicit aggressive responses from many local birds and even leading to it being mobbed by its own foster parents! Often extending its shameless begging repertoire to any passing bird, it seems the parental urge of other species does occasionally extend to ensuring t
his bare-faced cheat will continue to be fed by all and sundry until full independence finally sees it foraging for its own food.
The extended adolescence of Tawny Owls means any fledged young by mid-June will not only still be hanging around their parents’ territory, but also utterly reliant on any food brought to them for some time yet. Tawny Owl expert Dave Culley has followed his neighbourhood pair through a number of breeding seasons. Breeding in a small yet wooded suburban location in Cheshire, Dave has found that in April the owls’ diet consists of around 40 to 50% birds. But by June as much as 90% of all the prey caught and brought to the youngsters will be feathered. With the constant pressure to find sufficient food to feed their young, the adults at this time of year will capitalise on the easy prey of recently fledged birds, even hunting during the day when the opportunity arises. With numerous cameras set up throughout his owls’ territory, Dave has even managed to film one of the Tawny parents snatching a female blackbird incubating a clutch right off her nest!
Like their Tawny counterparts, young fledged Peregrines will also be some way off being able to feed themselves by mid-June. Gaining confidence in the air will be their first task and as they slowly master the necessary skills, their first flying missions will see them relentlessly chasing their fellow siblings and parents. In those locations where three or more young have successfully managed to fledge, this can be an exciting time to watch Peregrines, as all the juveniles tear after any adult returning with food. The difference in flying ability between adults and young will initially be striking, but by steadily learning the vast array of tricks needed to survive, they will hopefully soon be up to speed. Able by now to dismember and feed on a complete carcass on their own, the youngsters will still be very much home birds and not dare to venture too far away from the site from which they hatched in late April.
Despite the oldest Robin ever recorded by the BTO being a bird from Fylde, Lancashire, which lived for over eight years and four months, average life expectancy of the nation’s favourite bird is thought in reality to be a meagre two years. With such a short lifespan, it’s no surprise that Robins are keen to produce as many clutches as possible, meaning by the middle of June many pairs could already be well into feeding their second brood of the year. With daylight lasting over 16 hours by this time of year, the Robins will be keen to take advantage of these long summer days to keep their brood well fed. As with the first clutch, it will take the second brood no more than 13 or 14 days before the desire to unleash themselves on the world proves overwhelming. But as the speckled and helpless young will still need help from their parents for a further three weeks after fledging, the adults will have an important decision to make – whether to stick or twist!
As many Robins see their second brood fledging, those paired-up Swallows feeding the season’s first young will also be constantly on the go as they attempt to keep up with their growing chicks’ insatiable appetites. The emergence of the first pin feathers at around day four or five will coincide with the youngsters becoming even more ravenous. A couple of days later on and the chicks’ ability to maintain their body temperature in all but the worst weathers will then see the female press-ganged into helping her mate find enough food to support their growing brood. A study of Scottish Swallows by Angela Turner recorded the number of visits made to a brood of five chicks back in 1980. At just a day old, the chicks were fed an average of six times an hour, which was then compared with 17 visits per hour at six days old and around 29 times an hour after 10 days.
In order to pack in so many visits, most adults will hunt close to the nest location, rarely foraging more than 600m away and frequently even closer. Where Swallows have nested colonially, the feeding ranges of neighbouring birds will also overlap, particularly at traditionally rich feeding sites, such as around water bodies, or near cattle. The food the adults bring back to their chicks will also vary according to the time of year. Earlier in the season, for example, flies tend to be more abundant than aphids, and so for the first broods, horseflies and hoverflies are thought to form an important component of the chicks’ diet. These large, mobile insects require more energy for the adults to hunt, so fewer can be caught on each foraging trip, but as they provide far more energy than smaller insects, it seems worth the extra effort to seek them out. When the adults are collecting insects for the chicks, they will usually catch a good number, which are packed together in a salivary ball (or bolus) in the throat, before returning to the nest. Angela Turner tried to count the number of insects in each visit, and recorded anywhere from just one insect to 126, with the average number amounting to 18. In order to rear a brood from hatching to fledging it has been calculated that the adults may need to catch as many as 150,000 insects. In addition to this high-protein invertebrate mix, the adults will also provide their chicks with grit to help grind up the food in their gizzards, so aiding digestion.
Fed on such prodigious quantities of food the chicks will grow quickly, with days three to ten being the period when weight gain accelerates the quickest. Flying in with food, it is the parents who appear to judge how hungry each chick is, with the intensity of begging a key factor, before then deciding who gets the meal. Certainly when food is plentiful, and during the course of the day, each chick is thought to receive a roughly similar amount of food. Both parents feed the chicks directly, but the male’s effort can vary considerably between individual birds, with the more attractive longer-tailed males often being far more dilatory than the shorter-tailed males. This might not be entirely down to lethargy on the part of the longer-tailed males but possibly due to being less efficient foragers as a result of drag created by their long streamers.
For the first few days of the Swallow chicks’ lives any waste will be removed by the adults in the form of faecal sacs, but by 12 days of age, their toiletry skills will have improved sufficiently for them to begin painting the floor below the nest. After a couple of weeks the chicks should also be well feathered, and be topping the scales at 23 or 24g, making them even heavier than their parents. After this top weight has been reached, the chicks will then usually begin to lose a few grams as excess calories are burned by the constant exercising of their wings. Needing to fly competently the instant they fledge, they will still need a third week in the nest, during which time their flight muscles must mature sufficiently for them to propel themselves into the air when the moment comes. To ensure this first flight is a success, the chicks also spend an enormous amount of time preening to make sure they will be instantly flightworthy at take off.
Unlike the busy Swallow nests, many of those which belonged to Blue Tits in southern Britain will have already been vacated as the juveniles learn the art of searching out caterpillars in the tree canopy. Over the next few weeks, with the exception of their flight and some tail feathers, much of the youngsters’ hastily acquired dull plumage will be replaced as they prepare for colder times ahead. Squeezing through the hole hundreds of times to feed their chicks will also have made their parents’ feathers worn and frayed, leading to many adults starting their moult even before their chicks had even fledged. But as the adults will still need to be able to fly competently for the entire duration of the moult, the whole process can last as long as 80 days and so will not be completed until the autumn. Blue Tits tend to moult in a symmetrical fashion, with rarely more than one primary flight feather missing from each wing, to ensure the birds are still able to fly in a balanced fashion. The instant an old feather is shed, a new one will then start to form from special cells in the skin. Moulting is an energy-demanding process, and the replacement of body and contour feathers will also temporarily reduce the birds’ thermal insulation. So an increase in their intake of food should not only power the replacement of feathers but also keep the birds warm.
Not ready to begin their moult just yet, any adult Nightingales that managed to successfully raise a brood should currently be still helping to feed their chicks. Often staying together as a family for around two weeks at least, by th
e end of the first week the youngsters should slowly be starting to find their own food. Before the young fledged, the parents are believed to have foraged strictly within their clearly demarcated territory, but with their youngsters now mobile, the territoriality quickly breaks down, leaving the family free to wander further afield and to potentially richer feeding sites.
By mid-June, Lapwings should also be leaving their breeding grounds as both juveniles and adults join post-breeding flocks further afield. These flocks will provide a comfort blanket for all as the young learn the best habitats in which to feed, while the adults seek sanctuary while slowly shedding and replacing feathers worn out during the breeding season.
Breeding north of the Arctic Circle on the maritime Arctic tundra, those pairs of Bewick’s Swan intent on breeding should by now be sitting on their clutch of three to five eggs. Even though the male will take turns to sit on the eggs, it seems he may well in fact be doing little more than preventing them from becoming chilled or eaten by predators, as the responsibility for most of the incubation lies with the female. Bewick’s Swans are extremely shy during the breeding season, and being free from disturbance is an important factor in deciding how successful each pair will be in raising chicks. Any humans approaching to within a few hundred metres of the nest will initially cause the sitting swan to hide and if the intruder continues to move even closer this will result in the adult swan retreating to a nearby pool or lake. More natural predators on the tundra include Arctic Foxes, Wolverines, Arctic Skuas and Herring Gulls and they will often try to strike when the adults are away from the nest. Of these, Arctic Fox is thought to be the chief predator of eggs and young cygnets, and one theory believes that more Bewick’s Swan eggs and young are taken in those years when the population levels of the foxes’ favoured food, lemmings, are much lower.
