by Mike Dilger
Late May
Safely entombed in their fortified subterranean chamber, a high proportion of all the Kingfisher chicks that manage to hatch should successfully make it to fledging day. But surely the far sterner examination of the youngsters’ ability to defy the odds of reaching parenthood will only begin once they learn how to catch fish. Like many bird species, the young all tend to fledge in one day, often with gaps of 10 to 20 minutes between each youngster’s leap of faith. For those that don’t manage to fly immediately to safety from the entrance hole, and tumble down into the water, there is a very real possibility that unless they can flap to the bank side they will quickly drown. Once the young do manage to make it to a riverside perch, they won’t return the nest chamber again, but will instead have their valiant efforts rewarded as their parents either bring them a meal to their new perch, or whisk them off for their first fishing expedition.
If the young naive Kingfishers are to have any chance of pulling though then they must hone their fishing skills as quickly as possible, with many fledglings pressed into diving on the very day they fledge. Their parents’ practised technique makes a physically demanding and technically accomplished skill look effortless, and so as the youngsters attempt to emulate the ‘professionals’ there will inevitably be a fair number of mishaps along the way. Some juveniles, having dived in, may simply become waterlogged and drown, while others will struggle, yet somehow live to dive another day. Of course during this period of intense tuition, the juveniles will also be fed by their parents who are able to quickly locate their young charges amongst the bank-side foliage by their ‘chip, chip’ begging call. This ‘safety net’ will not last long though, particularly as the parents will be keen to raise at least one more brood and so from around day four the adults’ response to begging will change from that of feeding to rebuking. This ‘tough love’, however, is merely a precursor to even rougher treatment, as the parents shortly afterwords harden their attitude even further to mercilessly chasing them out of their territory. Evicted irrespective of the state of their fishing skills, the youngsters will need a fair bit of luck and to learn quickly if they’re to survive through to next spring without either starving, drowning or being predated.
Unlike young Kingfishers, juvenile Lapwing are able to feed independently almost immediately upon hatching, although the Lapwings’ main issue is not a lack of food but avoiding the high levels of predation seen on many wader breeding grounds. For those Lapwing chicks that hatched in late April, while still not quite able to fly, a much enhanced mobility should already have exponentially increased their chances of successfully fledging next month. The last feathers to emerge will be those from the tail, and the paler tips to the greenish-bronze feathers across their back and wings will give the youngsters a distinctly ‘scalloped’ appearance as they continue to feed under the watchful eye of their attentive parents.
Some three weeks after leaving the nest, all the young Robins should by now have fully graduated from fledging academy, but with their trademark red breast not due to make an appearance until later in the summer, they will still look utterly different from their parents for a while yet. This decidedly speckled and camouflaged plumage will not just help them avoid detection by Sparrowhawks, Stoats and cats, but also give them a free pass under the radar of any territorial adult Robins. Now temporarily released from the responsibility of caring for his brood, the male Robin will be free to return to his mate, who should be incubating her second clutch, which if all goes according to plan, will hatch in early June.
Having already emerged from their tree-hole cavity around three weeks ago, those Tawny Owl youngsters managing to successfully navigate the difficult first couple of weeks should by now be flying much more strongly, leaving them free to investigate their parents’ territory. The boundaries marking the full extent of their parents’ universe will be learnt quickly as the youngsters immediately shy away from any neighbouring adults or sounds of any broods in adjacent territories. While making their first exploratory steps, the young will still have made little, if any, attempt to catch their own food, remaining utterly reliant on their parents for all their meals. Even with the prolonged level of support given by mum and dad, it’s thought that their care is restricted purely to the provision of food and defence against predators, and there seems little evidence that the adults actually train the young how to hunt on their own. This is a skill, however, that the young will not be able to put off practising for much longer as once they disperse into the surrounding countryside later in the summer they will very much be on their own.
For those young Peregrines hoping to fledge in early June, late May should see the nest site as a hive of activity. As the juveniles’ wing and tail feathers develop strongly, the contour feathers will also begin appearing in lines and patches around the back and breast, leading to the preening of all these newly emerged plumes turning into a major occupation. The youngsters will also be ruffling their feathers on a regular basis, to help shake out any loose down and ensure the feathers are properly aligned to ensure maximum insulation during any cold and wet spells. The young will also be rapidly increasing their exercise regime by walking around and wing-flapping as they work on strengthening their flight muscles. This increased mobility will in turn enable them to defecate over the edge of the tower block or cliff face, so helping to make sure their freshly emerged feathers don’t become prematurely soiled. As the food continues to be brought in, by around their 31st day the chicks should be capable of ripping up any plucked and headless prey by themselves, and by the time fledging arrives, at around 40 days, they should be competent in demolishing an entire fresh carcass. As the young will soon discover though, actually catching their own prey will be a different ball-game altogether.
In the Blue Tit nests of southern Britain, late May should see the nest activity reach fever pitch as the chicks’ insatiable appetite increases the demand on their beleaguered parents. As the chicks are less likely to need brooding by now, both mother and father will be press-ganged into working from dawn to dusk to ensure enough food is collected, with a brood of ten chicks estimated to dispose of close to 1,000 caterpillars a day! Feeding at a rate of possibly a visit every 90 seconds will soon see the adults’ plumage looking pretty ragged, or effectively like they’ve just been dragged through a hedge backwards – which in many ways they have! The items and quantity of food brought in to feed the chicks will vary according to where the nest is sited, with brood sizes in farmland and gardens often being lower than for those pairs nesting in prime deciduous woodland habitat. For any pairs rearing chicks in or close to mature trees, the caterpillars of the Winter Moth and Green Oak Tortrix are thought to provide a substantial component of all the food brought in to the chicks. In some years the sheer number of all the caterpillars munching away in the canopy is so high that the sound of the larvae’s frass (or excrement) falling to the ground can almost sound like rain. With each oak tree thought to be capable of holding as many as 100,000 caterpillars, the first flush of foliage can even be completely stripped on some occasions. Once the Winter Moth caterpillar reaches full size on a diet of fresh young leaves, it will then lower itself down on a single gossamer thread to pupate on or below ground. This contrasts with the Green oak Tortrix moth, which always pupates in a rolled-up oak leaf.
In the years when both caterpillars are abundant and the Blue Tits have timed the hatching of their broods to perfection, many of these caterpillars will not make it to the pupal stage, as their development becomes rudely interrupted by being plucked off a leaf and subsequently rammed down a hungry Blue Tit’s throat! So important is this brief annual harvest for Blue Tits that in years when numbers of caterpillars are lower, or the birds’ timing is a touch out, many chicks will simply starve in the nest. In those broods receiving plenty of food the young will quickly feather up, with the nest quickly beginning to look like it’s about to burst at the seams and decidedly unfit for purpose. There will also be plenty of stretching a
nd whirring of wings at this stage as the young Blue Tits dispense with the last of the down and build up their flight muscles. Knowing full well where the entrance (and exit) hole is due to constantly watching the comings and goings of their parents, after just a couple of weeks the chicks won’t be able to resist jumping up for their first views of the world beyond the confines of their nestsite or nest box.
Finally, some 3,500km away from the nearest British Blue Tits ready to fledge, the Bewick’s Swans will at last have begun to arrive at their remote Arctic breeding grounds. Until recently, very little was known about the Bewick’s Swan’s summer haunts, as the Nenets Autonomous Region has only recently opened up to western ornithologists, and even for Russian scientists, the vast, sparsely populated terrain makes visits for any length of time difficult. Those Bewick’s Swans overwintering in Britain are, in essence, thought to breed in a broad strip along the Barents Sea coast, anywhere from the Malozemelskaya tundra in the west, right through the Bolshezemelskaya tundra and as far as the Yugorsky Peninsula some 950km further east. This huge expanse of land entirely confined within the Arctic Circle mostly consists of maritime tundra and low-lying marsh that is riddled with pools and lakes, criss-crossed by river channels and dominated by a mosaic of moss, lichens and sedges.
The known breeding, moulting and pre-migratory sites of Bewick’s Swans in the Arctic region of the Russian Federation.
Any offspring reared during previous breeding seasons, and which spent the winter alongside mum and dad, will by now have already dispersed giving the parents the opportunity to breed unencumbered. One crucial factor which strongly determines individual nesting success in this harsh, unforgiving climate will be the age and experience of the birds. As most pair-bonds don’t even become established until at least three or four years of age, it’s distinctly possible that many pairs will not even attempt to breed for the first time until even older than this. Researcher Eileen Rees from the WWT has made a study of Bewick’s Swans on their summering grounds and believes only between 20% and 64% of established pairs will nest each season, with the climate ultimately dictating collective breeding success. In those years when spring arrives later and the summer ends up being colder than average, clutch sizes will additionally tend to be smaller. In fact, upon arrival, a number of pairs may decide an attempt is not even worthwhile and will not even bother holding a territory, but will instead join up with those birds still too young and inexperienced to form gregarious non-breeding flocks on shallow lakes and marshland nearby.
However, those pairs keen for their journey not to have been wasted will suddenly begin actively shunning the company of other swans, as the most experienced pairs return to locations that led to successful breeding attempts in previous years. Invariably they will arrive to find their old territories still covered in snow and ice, but these conditions won’t stop them marking out the boundaries and actively defending their reacquired real estate from any swans they perceive to be either trespassing on the ground or using their airspace. Mating is thought to occur close to, or on the breeding grounds, and the displays prior to copulation include subtle ritualised head-dipping, followed by the birds rising out of the water with their wings extended, while calling vigorously. With so many predators roaming the tundra, their next job of deciding the specific location for the nest will be crucial, as the brief Arctic summer will not afford many second chances to those pairs with either chilled or predated clutches.
Like the Bewick’s Swans, the sparsely populated areas where Waxwings nest means the breeding ecology of this species is also little known. In locations with plenty of suitable habitat, there seems to be a colonial element to their breeding, with the distinctive sociability that is normally such a feature of this bird in its winter quarters, not breaking down completely when nesting commences. In studies of captive Waxwings, the male was observed to select the nest location and the few observations of wild birds made suggests they favour old, stunted and lichen-festooned conifers, choosing anywhere from three to 15 metres above the ground to rear their young. As many of the birds will have already paired up before reaching the breeding grounds, the male will waste little time in declaring his territory from a tree-top close to the nest with his simple high-pitched trill. This statement of intent may also serve to encourage the female to cement their bond by joining him for a duet.
Mating is thought to occur both close to and on the breeding grounds, with the male continuing to feed his mate a combination of fruit and insects to ensure she will be in good enough condition to produce her clutch. Built by both the sexes, the female is believed to assume the larger role in nest construction as the base is built up with a cup of thin twigs, before being lined with Reindeer Lichen, moss and fine grasses. The period between when nest-building is finished and incubation is initiated is thought to be the only time when the normally placid males show aggression towards their neighbouring rivals. During this window any intruder perceived to be interrupting business at will be sent packing by a combination of bill-gaping or snapping, as the incumbent male presses home his advantage without having to resort to physical violence.
For any Cuckoo chick that has successfully evaded detection in its foster parents’ nest throughout incubation, violence will quickly become order of the day upon hatching. Weighing in at little more than 3g, the Cuckoo’s egg has been carefully sculpted by evolution to mimic both the size and pattern of the chosen host species’ eggs as closely as possible. Incubated in amongst the host bird’s clutch, the alien chick will also be blessed with a head-start over the rest of its host’s brood. Having been laid with a partially developed embryo, means the Cuckoo chick could hatch in a remarkably quick 12 days after its mother’s clandestine deposition. Hatching earlier brings considerable advantages to the Cuckoo chick, as the host’s own clutch of eggs, or very young chicks, are certainly much easier to eject from the nest than, say, older host chicks, which may have already put on a substantial amount of weight.
The credit for the first detailed description of Cuckoo chicks ejecting host eggs, or young, remarkably goes to Edward Jenner, the celebrated scientist who effectively invented vaccination. Before his seminal work on smallpox, he published a paper on the Cuckoo’s nesting habits in 1788, which led directly to his election to the prestigious Royal Society the following year. At the time his assertions were met with widespread disbelief and initially rejected; however, as other naturalists subsequently backed up Jenner’s observations he was quickly vindicated. What Jenner first recorded must surely go down as one of the greatest Machiavellian feats in the natural world.
It’s generally not until around eight or ten hours after hatching that the Cuckoo chick will have garnered sufficient strength to begin the devious business of ejecting the host eggs or chicks. Despite being naked, pink and blind the chick has a broad back complete with a shallow depression, and by wriggling around in the bottom of the nest at some point one of the host’s eggs or helpless chicks will finally come to rest on its back. By then using its legs as a brace against the side of the nest, and its wings to hold the egg or host chick in place, the young Cuckoo will then begin the exhausting process of hauling its cargo up the wall of the nest. Working in short bursts with frequent rests, as soon as the egg or chick finally reaches the rim, one last quick jerk will see it pushed out of the nest, and in the case of the Reed Warbler, straight into the water below. In the nests of small hosts such as Reed Warblers and Meadow Pipits, it might take less than 20 seconds to evict an egg, but having seen this happen many times, Cuckoo expert Nick Davies reckons the average time taken is around three to four minutes per egg. Needing also to recoup its energy in between evictions, the disposal of an entire clutch might take anywhere from three or four hours to a couple of days if the chick has to eject large host young. After four days, this ‘ejecting behaviour’ then suddenly disappears, by which time the Cuckoo should have become the last chick standing! Oblivious to this blatant act of skulduggery, the unquestioning host parents will t
hen simply devote their entire attention, and food supply, to the Cuckoo in the nest.
Hatching out in southern England, Nightingale nestlings certainly don’t have the killer instinct of a Cuckoo chick, and compete on a fair and level playing field with their fellow siblings for the food brought in. Instinctively begging soon after hatching, the young are initially brooded by their mother, leaving the male as the sole provider of food during the early stages. Like Blue Tits, the Nightingale pair will aim to synchronise their brood to the precise moment when concentrations of caterpillars are at their highest. Any tiny caterpillars or other morsels brought in by the male are passed initially to his mate, who will in turn feed the small, naked and blind young. This arrangement won’t last long, and as the chicks’ appetite grows, both parents will be forced into foraging for larger caterpillas to keep up with the demand.
The British naturalist Oliver Pike, in his book The Nightingale: its Story and Song, published in 1932, spent many hours watching Nightingales on their breeding grounds. He reported on one nest where the adults came in every minute for nearly three hours and the four young were always ready for their meal. Before the young’s eyes were open, Pike observed the female making a low ‘zee-zee-zee’ call to prepare the young for her arrival, but later on as the chicks were able to see, this call was rendered redundant, as beaks suddenly shot up at the first sight of her return with food. Watching the nest from his hide with a periscope, Pike didn’t think that the parents travelled far from the nest and that all the food was collected strictly from within their territory. Although the male will still sing at this stage, it will be only sporadically, with any bursts heard presumably giving male chicks in the nest the opportunity to listen and start learning the complex songs they will need to have mastered by the following year – providing they manage to both fledge and successfully negotiate a return trip to Africa!
