by Mike Dilger
The appearance of the chicks will result in the parents suddenly turning much more aggressive and intolerant of trespassers, driving any non-related Peregrines and potential predators away from the nest site. With just their first coat of down to protect them from the elements the young can be incredibly prone to chilling, and so will initially be brooded almost continually by the female. Huddling together to conserve heat, the young are then fed tiny morsels of food by their mother as they take the first of many meaty meals caught and brought in by their diligent father. Even when the chicks are small it won’t take long for a hierarchy to develop within the brood, with some chicks always demanding to be fed first, while any weaker chicks are forced to feed afterwards. In lean times, small chicks can often quickly disappear from the nest, but in years of plenty the entire brood may well stand a good chance of surviving, certainly as far as fledging.
Also making an appearance before the start of May, the Kingfisher chicks, like those of the Peregrine, tend to emerge at the helpless end of the scale. Hatching into their dark, dingy nest chamber, the chicks are pink, blind, devoid of feathers and will be totally dependent on their parents. With usually just a few hours between the hatching of each chick, the adults’ first act is to remove the broken eggshells, presumably to maximise the space in the nest chamber. The chicks will often take their first fish meal within just a few hours of hatching, and as the prey items are not dismembered by the adults, but eaten whole and head first, the parents will initially bring in quite small fish of around 5cm or less. Sometimes it can look like particularly young chicks are struggling to swallow a big fish, but their guts are very effective at quickly breaking down the food to make room for the rest of the meal. Unable to see for at least the first eight days, it seems that during this period the young respond to the light being blocked out from the tunnel as the sign that a parent’s arrival with food is imminent.
For those Tawny Owl chicks hatching in early April, by the end of the month their eyes should be open and their bodies completely covered in a grey jacket of down, far more adept at keeping them warm than the sparse covering with which they hatched. As the chicks become more able to insulate themselves against the vagaries of the British spring, this should in turn free up the female to help her mate find enough food to supply the brood’s ever-increasing appetite. Despite now spending less time with the chicks, the female rarely travels far, as she leaves her partner responsible for foraging further afield. When food is brought in by either parent, the nestlings will by now be jostling with each other for the best position to take any food offered. This undignified scramble also involves much noisy begging and there is some evidence that the adults tend to feed the chick calling the loudest. Any chick that has secured a good prey item will also call vociferously immediately afterwards, and this could help it defend any meal too large to swallow instantly, as at this stage the youngsters are still too small to tear it up. Even when the adults are not present, the chicks will still call frequently, possibly in order to establish a pecking order, which could mean all the difference between life and death in those years when the demand for prey outstrips supply.
Faced with having to find ever more food for their growing chicks, the Tawny Owl parents may even be forced to hunt during the day just to keep up with the incessant demand. Tawny Owl expert Dave Culley has carefully studied the diet of his pair of Tawnies in suburban Cheshire and found it far more varied than just mice and voles. The chicks in his nest were fed a diet of around 50% small mammals in late April, but as other young birds, such as Blackbirds and Robins, fledge from surrounding nests, songbirds soon become the major share of the young owls’ diet. A couple of weeks after hatching will also see their wing and tail feathers emerging from the mass of down, and although skeletal growth of the chicks generally finishes much earlier, the flight feathers will continue to grow even after they have left the nest. At a fortnight old, the chicks are now looking far more ‘owl-like’, and will begin to exercise, preen and scratch much more. Head bobbing can also be seen – a technique used to gauge distance, and a skill they will need to thoroughly master before they begin hunting for themselves later in the year.
Three days after hatching, and providing the Robin chicks remain well fed, the appearance of quills all over their skin indicates that feather emergence should quickly follow. A couple of days further on will see the chicks’ eyes also begin to open, and such is their rapid rate of development that by the tenth day their bodies will be more or less fully feathered. With the Robins at the point of fledging less than two weeks after hatching, a full brood will see the nest literally bursting at the seams. Still devoid of the famous red breast until after their first moult, the heavily speckled youngsters will by now have learnt the art of crouching down and flattening themselves if danger threatens. But as soon as the coast becomes clear, they will instantly change their tune back to that of noisy beggars, with a sea of yellow gapes and cacophony of calls confronting any parent turning up with food.
Certainly in southern Britain, as April draws to a close most female Blue Tits should have laid close to their entire clutch, with incubating generally beginning just before the final egg is laid. As laying takes place, the female sheds feathers from her breast and belly to expose a large area of skin that becomes exposed, wrinkled and almost purple due to the rich supply of blood vessels running just below the surface. When this brood patch is combined with the insulating properties of the nest and feathers from around the bird’s breast, which operate as a skirt to seal in the heat, this should easily provide sufficient warmth to incubate the eggs at the optimum temperature for their development.
Only too aware that the time for synchronised egg laying will be rapidly approaching, from securing a burrow and carrying out repairs, the male Puffin will turn his attentions to consummating the relationship with his mate. For established pairs, Puffin courtship may have begun even before the birds make their spring landfall, with most matings tending to take place on water. Invariably instigated by the male as the pair bob around like corks on the surface, he will make his intentions perfectly clear by flicking his head back amid a fluttering of wings. If the female is not interested she will constantly dive to keep him at bay, but if he catches her in a more receptive mood, swimming low in the water will encourage the male to mount her as he uses his wings to balance. The coupling is once again a very brief affair, usually lasting less than 30 seconds, and afterwards the male will usually guard his female to ensure he is not cuckolded before his mate lays their single, precious egg in early May.
Arriving later than the males, most female Swallows will generally find a partner within three days of returning to their traditional nesting sites. However, the ‘fairer sex’ can still be quite choosy and the male will need to use all his persuasive powers if a female is to select him for the breeding season. A good nesting location will play a large part in attracting a female, as will the male’s looks, with Swallow researcher Angela Turner stating that ‘in Europe at least, males with longer tails are clearly the choice of discerning females’. The fussy females also seem to additionally prefer males with outer tail-feathers of the same length, those individuals with larger spots on their tail feathers and any with particularly bright red coloration in the face. In essence it seems in the world of the Swallow that long tails and bright colours are an indication of good health and also possibly more experience, as more sickly males will not have fed sufficiently well for the extravagant feather growth.
Reaching ‘first base’ by securing a female’s attention, the male will then make repeated flights up to his nest in an attempt to entice her into admiring his residence. If she is then enticed over for a closer inspection the male’s next move will be to land close by in order to show off his fanned tail, while uttering notes of encouragement, as he attempts to seal the deal. In locations where a number of pairs may be nesting in a loose social flock, some particularly handsome and persuasive males may be able to secure two females to mate
with, while short-tailed males may attract far less interest. For those males lucky enough to secure at least one mate, the next job will be to either repair an old nest – should one still be present in a reasonable state – or alternatively start building a new one from scratch.
As the female Nightingales arrive back, they should already find their breeding grounds carved up into territories as the males implore the females to visit their own real estate. The male Nightingale is of course famous for singing both day and night, but exactly when their song is produced conveys a different meaning. The diurnal song is mainly directed at approaching rivals and associated with holding territory, while the nocturnal song is thought to be more of a long-distance advertisement to any females looking for a partner. During the day the males sing from several perches and regularly change position with the start of each song – this contrasts with the nocturnal song, which is usually delivered from one particular perch that may be favoured for several nights in succession.
Although physical fights between males do occasionally happen, the main form of defence and attack is the territorial song. Adjacent males intent on courting a visiting female will often have long song-duels at the territory border, which may then occasionally escalate to a bowing threat posture. If this aggressive and overt display has still not persuaded either male to back down, they may then chase each other through the trees, singing as they go, until a winner emerges. Once the female has made her choice, the pair will then undergo a ritualised pair bonding where the male hops around on the ground below the female as he pours forth his finest repertoire. During the delivery of this virtuoso performance he will often then seal the deal by hopping up to her branch while raising and fanning his tail to top off the display. With the bond cemented and the relationship duly consummated, the male will then continue to converse with his mate around the territory through short and fragmented bursts of song. With the nocturnal song having thus achieved its main aim, this slowly begins to tail off as the pair prepare for the next phase of the breeding season.
With Cuckoos still dotted at various sites across Europe, late April may well be their last chance to feed up before the final leg of their migration sees them converging on the English Channel as they prepare to cross into Britain. Depending on the weather some Cuckoos can be heard calling in Britain in April, but the data from all the Cuckoos transmitting their position to satellites as part of the BTO’s research suggests there is remarkable uniformity, with the first week of May being the time when most males seem to arrive back. In the four springs that Chris the Cuckoo successfully navigated his way back to Britain, his arrival dates were 1 May in 2012, 4 May in 2013, 25 April in 2014 and 27 April in 2015.
Remarkably, while many Cuckoos are within a hair’s breadth of reaching Britain, in those springs following a ‘Waxing’ winter there may still be a small number of birds dotted about the British countryside yet to leave. With no confirmed breeding records of Waxwings in Britain, these late departees have presumably decided that staying and feeding in Britain with a view to returning rapidly to their breeding grounds is a more favourable tactic than leaving earlier in the year and taking the slow train. For those early departees taking the leisurely continental route, late April should see them closing in on their summer destination. Their approach to the breeding grounds is believed to be the time when pair bonds form, primarily because there seems little evidence of courting birds amongst the overwintering flocks in Britain.
Still in no immediate hurry to reach their breeding grounds, most Bewick’s Swans that overwintered in Britain will still be busily foraging at a variety of sites across Estonia, the Gulf of Finland to the north and even the most western parts of the Russian Federation. Keen to feed as well as possible while waiting for the big thaw to reach the maritime tundra further north, the swans will need to have put down plenty of reserves in preparation for heading north-east across the vast forest tracts of the Republic of Karelia, to the appropriately named White Sea and all points beyond.
The believed spring and autumn migratory routes of Bewick’s Swans between their wintering grounds in Britain and northern Europe.
May
For the naturalist, May is simply a fabulous month for watching wildlife, making it difficult to know where to turn. As the leaves on the trees unfurl, our woodlands take on a vivid green hue, which contrasts with rural hedgerows being painted white as Hawthorn, or May Flower, comes into blossom, while the yellow blaze of Gorse lights up our moorland and heathland. During this month of ‘May-hem’, Badger and Fox cubs will be emerging from their underground setts and earths, while any mammals which spent the winter in hibernation will be playing catch-up as they get stuck in to the fighting, feeding and breeding season. The dawn chorus at this time is deafening, as all the migrants compete to make their voices heard above our resident birds. The warmer ambient temperatures this month will also produce a super-abundance of invertebrates, on which parents with hungry chicks will be able to capitalise, and with the sun rising steadily earlier and setting later they shouldn’t be short of daylight in which to forage either. Away from our shores, those birds that spent the winter in Britain should also be completing their migration as they reach distant breeding grounds spread right across both northern Europe and the Arctic regions of the Russian Federation.
Early May
The ‘advance guard’ may have already arrived during the last few days of April, but early May has to be the time to listen out for the first Cuckoos arriving back after a winter spent in the hot, humid forests of Central Africa. Surely one of the most recognisable calls in Britain, Wordsworth’s ‘wandering voice’ seems the very essence of spring, and yet is produced by a bird that is seen by surprisingly few people. Breeding throughout much of Britain, Cuckoos can be found in an array of habitats, with the exception of built-up areas, but most commonly favour reedbeds, moorland, woodland and agricultural land. Certainly amongst British birds, the Cuckoo is a bird with a unique lifestyle, being the only British species to never build a nest but preferring instead to lay its eggs in the nests of smaller foster birds, or hosts, which incubate and rear the young to their own detriment – behaviour that is called ‘obligate brood parasitism’.
The distinctive ‘cuck-oo’ call is only produced by the males, who usually arrive a week earlier than the females, and start advertising their presence as soon as they turn up at their respective breeding grounds. Rather than holding a territory in the conventional way, the males tend to have a ‘song range’, which can vary in size but tends to average around 30 hectares. This ‘range’ may well overlap with other competing males, but also crucially will encompass the ‘breeding range’ of at least one female, when they arrive back a touch later. The famous disyllabic call can sometimes be monotonously repeated up to 300 times in succession and is capable of carrying up to 5km in favourable conditions. Anyone who has ever tried to observe a calling Cuckoo knows their voice has a ventriloquial quality, which is a result of the bird turning its head while calling. Some naturalists with a good musical ear claim to be able to separate individual birds on call by subtle variations in pitch and tempo, and so it seems highly likely that the male and female Cuckoos must also be able to recognise each other’s calls.
The Cuckoo is also the only British bird known to actively seek out the seemingly unpalatable hairy and brightly coloured caterpillars which form such an important component its diet. But this food supply is rarely abundant early in the season and observations seem to suggest that the Cuckoos substitute the caterpillars with a whole variety of beetles, spiders, ants, flies and worms until their favoured prey item comes on tap. The Cuckoo’s main feeding technique involves scanning the surrounding environment from a perch. When the movement of a suitable item is spotted the Cuckoo will fly down to make a capture, either then demolishing the prey on the spot or returning to a perch to deal with the catch. Before being eaten, any large caterpillar is worked through the Cuckoo’s bill from end to end, prior to being given a
quick, violent shake to ensure the larva’s gut contents are ejected before the eviscerated item is then swallowed. The caterpillars’ hairs collect in the Cuckoo’s stomach lining, which is then periodically shed before being regurgitated as a pellet.
Female Cuckoos seem to be incredibly site-faithful, with the vast majority returning to the same location year after year. Each female Cuckoo has evolved to specialise on one particular host species, which will be victimised throughout the lifetime of the bird. Although female Cuckoos have been recorded laying their eggs in the nests of over 100 different species of birds according to the BTO, just five hosts account for 90% of all parasitised nests. In marshland Reed Warbler is the main host, and in moorland and heathland, Cuckoos opt for Meadow Pipits; Dunnocks or Robins are mostly targeted in woodland and farmland, while the Pied Wagtail is often selected in open country. This pre-ordained selectivity divides the Cuckoo into several host-specific races, or ‘gentes’ - a term coined by the famous Cambridge zoologist, Alfred Newton.
On arrival back at their traditional site the females will immediately attempt to take over a distinct breeding range of around 30 hectares, which will commonly hold a healthy population of her host species, and into which she will plan to lay all her eggs. Often this appears to be an exclusive territory, but at some locations it can contain a number of females with overlapping breeding ranges. When there is some overlap, often just one female will dominate proceedings and lay far more eggs than the other subordinate birds. Early in the season any newly arrived females will often be harried by amorous males, and so they will prefer to a low profile until they’re ready to mate.
