by Mike Dilger
Early May should also see the arrival of the first Waxwings back at their breeding sites in the higher latitudes of northern Europe. Called ‘boreal’ in Canada, or ‘taiga’ in Russia, the huge tract of forest that covers large parts of Canada and Alaska, most of Sweden, Finland and Norway, and much of the northern Russian Federation east to Japan is considered the world’s largest land-based biome. Representing an astonishing 29% of the world’s forest cover, taiga is relatively low on biodiversity, when compared to, for example, the tropical forests, primarily due to the astonishingly low winter temperatures. With a record low of –53°C in the Russian taiga, many mammals will hibernate to avoid the worst excesses of the winter, while most birds will simply migrate to warmer and lower latitudes. But by July, the temperatures will often rise well above 10°C, and when this is combined with the long hours of daylight and scarce competition for the food available, the habitat should give hardy birds like Waxwings more than enough time to rear their broods before autumn brings the short breeding season rapidly to a close.
It’s generally assumed that most Waxwings overwintering in Britain will be birds from the taiga forests of northern Norway, Finland, Sweden and the north-western parts of the Russian Federation, which made one particular ringing recovery all the more astonishing. One Waxwing ringed as an adult male in Aberdeen on 31 March 2005 (during the large invasion of the winter of 2004/05), was subsequently reported to have been killed by a cat the following February in a village located in the Khanty-Mansi region of the Russian Federation, east of the Urals and north of Kazakhstan – or 3,714km from its British ringing location! This spectacular long-distance movement aside, of the 35 Waxwings ringed in Britain and reported elsewhere, 21 have been recovered from Norway, Sweden and Finland, with a further 12 thought to be actively migrating birds recorded from the near continent. Irrespective of the line of longitude to which the Waxwings return, they will always nest south of the latitudinal line where the trees finally give way to Arctic tundra. The taiga forest itself consists primarily of huge stands of Spruce and Pine, mixed in with Birch and plenty of fruit-bearing plants such as Bilberry, Cloudberry and Cowberry. Lichens are also abundant in these forests, and the hanging Witch-hair Lichen (Usnea) festoons many of the conifers in which the Waxwings will ultimately nest come the middle of June.
Deciding they too must head north, early May should see the majority of Bewick’s Swans on the next leg of their epic voyage, which will see them departing to the White Sea on Russia’s northern coast. Leaving from a wide variety of sites across Estonia, Latvia and the western outreaches of the Russian Federation, the swans will fly in a north-easterly direction, possibly over St Petersburg and into the Republic of Karelia, a sparsely populated land composed primarily of trees and lakes. This federal subject of the Russian Federation has a long western border with Finland, is demarcated to the north by a 630km coastline with the White Sea and to the south with a convoluted border which abuts Europe’s two largest lakes, Lake Ladoga and Lake Onega, themselves situated within mother Russia. It’s thought that the swans will either stop temporarily at these lakes or use them as way-markers while they take a north-easterly bearing, the direction which also represents the shortest overland distance to the White Sea. The brackish waters of the huge Dvina Bay and Dvina Delta, situated alongside the major Russian port of Arkhangelsk and within the White Sea, are around 1,000km from Estonia and represent an internationally renowned staging post for Bewick’s Swans, both on their spring and autumn migrations. With many having flown directly from the Baltic, the swans are then thought to feed on the eelgrass and stoneworts in the bay while waiting for the sea ice to recede. This area is considered so important that in spring 1996 18,000 Bewick’s Swans were estimated to have passed through the Dvina Bay region, a figure which at the time may have represented over 60% of the entire population of Bewick’s Swans from the European flyway. Upon arrival the swans are thought to rest and feed up for a short time before then continuing to filter in a northwesterly direction which also follows roughly along the line of the Russian Federation’s coastline. Passing through the strait that separates the White Sea from the Barents sea, the swans should be aware they’re on the home straight as they press on to the maritime tundra further along the coast.
Even before the Bewick’s Swans have arrived at their breeding grounds, early May back in Britain should see many Robins’ first broods taking their first leap into the big, wide world. Leaving the nest a mere fortnight after they hatched, the Robin chicks’ flight feathers will still be growing when they take their leap of faith, so the fledglings will still need a couple more days until they’re actually able to take to the air. At this stage many first broods will be abandoned by the female as she leaves them to be looked after solely by their father, in order to turn her attention to building another nest for her second brood. Despite dad’s best efforts, the first few days outside the nest can be brutal for an inexperienced, flightless Robin chick, with many simply starving or falling prey to a whole raft of predators. Heavily speckled to disrupt their outline and aid camouflage in the undergrowth, those chicks that have managed to survive their first septimana horribilis should slowly begin finding at least some of their own food.
With the Lapwing chicks also vulnerable to predation at this early stage, their father will assume the mantle of chief lookout and guard. Standing slightly away from the mother and chicks, and in a good location to spot any potential predators approaching his charges, he will harry any perceived threat until they are driven away. Stoats or Weasels will be mercilessly mobbed, dogs can be attacked and he will often circle above humans while alarm calling, in an attempt both to distract the attacker and give the beautifully camouflaged chicks a moment to crouch down and freeze. As is the case for many young chicks, mortality is highest in the first few days, with one Dutch Lapwing researcher reporting that despite the best effort of the parents, 60 to 75% of all chicks were lost to predators within the first ten days. After this unrelenting period the number of chicks taken seems to steadily decline as the young not only grow stronger, but also become more streetwise.
Able now to feed without needing their mother’s help in dismembering prey, the young Tawny Owl chicks will soon become keen to break free of the constraints of nest life too. In most years, early May should see them spending long periods of time at the nest entrance before finally pluking up the courage to make a bid for freedom a few days later. The oldest chicks are evidently the first to leave the nest and will often be encouraged out by the soft contact calls of their mother from a nearby branch. Unable as yet to fly, their mode of transport will be climbing as they use a combination of talons, bill and flapping wings to work their way up into the branches of the tree – a process unsurprisingly called ‘branching’. At this early stage many chicks will fall out of trees, only to end up on the ground, but they innately seem to understand this is not a safe place to spend any time and so are usually able to quickly scramble back up again. After having left the nest site the young will not return again, but rarely travel far and often spend the first few days huddled together as both parents continue to bring in sufficient food to meet their insatiable demands. Still a mass of pearl-grey down, with their wing feathers bursting through, the chicks will spend at least the first week out of the nest precariously perched amongst the branches before they build up enough courage to take their first, silent flight. This maiden voyage will often be nothing more grandiose than a short gravity-defying flap between two trees, and will certainly be a case of one small step for the Owl but a giant step for Tawny-kind.
Still a full month from fledging, the Peregrine chicks will nevertheless be putting on weight and becoming stronger with each passing day. Even at this tender age, preening, scratching and wing or leg stretching all become part of the daily routine, in addition to their favourite occupation of sleeping. As they begin to grow a second, warmer layer of down at around ten days the female will need to brood them less, meaning that unless the weath
er is wet, cold and windy she will begin leaving the nest for short periods. As their vision starts developing strongly, this will lead to the youngsters suddenly becoming more mobile. Able to observe any comings and goings from their lofty position will often result in a mad, noisy scramble towards any parent spotted arriving with food. At this stage the male will still be catching the majority of the prey for the chicks, but he will from now on also begin helping the female to feed the chicks at the nest. Arriving at the nest site, the adult dishing out lunch will pin down the plucked and headless prey with its powerful talons, before proceeding to rip it up and feed one morsel at a time to the chicks. As the young become increasingly more coordinated, noisy and hungry, the chunks of food they are able to deal with will increase in size.
In their tunnel nest, little will be heard from young Kingfisher chicks until their eyes start opening at around eight days. The power of sight will suddenly shake them into turning the volume up, leading to their constant churring calls frequently audible from the bank side, particularly when they’re hungry and waiting to be fed. Even before the first feathers break through their translucent skin, the blue colouring so characteristic of Kingfishers is very noticeable, and the imminent arrival of plumage is timed to match a huge increase in the chicks’ demand for fresh fish deliveries. As each chick is fed its fish it will then shuffle to the back of the pack to digest the meal and await its next turn. Any chick daring to get more than its fair share by queue jumping will often be pecked back into line by its hungrier siblings.
In those nests where the parents are able to catch enough fish, renowned Kingfisher expert David Boag calculated that each chick will be fed around every 50 minutes, so a typical nest could easily consume over 100 fish a day at its peak, and this figure doesn’t include those consumed by the adults themselves. By now the chamber will be reeking of regurgitated fish remains from both the chicks and their parents, but as the youngsters become more mobile they seem to be aware of this sanitation issue and so begin venturing down the tunnel to defecate rather than add to the mess in the chamber. Squirting out their white poo soon turns the tunnel into a slimy mess through which the adults must trudge through each time they return with food. This necessitates frequent bathing and preening sessions for the parents to ensure their plumage remains both flightworthy and waterproof. The sheaths that enclose the feathers will also begin poking through the skin at this stage, leading to the chicks quickly turning into a spiky mass of blue and orange. Interestingly, the feathers remain encased until they are virtually full grown, with the sheaths only dropping off shortly before fledging. This is thought to be an adaptation to protect the new feathers from the filth and squalor of the chamber, to ensure the plumage remains in the best possible condition for the moment the youngsters fledge.
With her clutch complete, early May should find many southern Blue Tits in full incubation mode. The sole responsibility of keeping the eggs warm and turned on a regular basis falls to the female, who will spend the entire fortnight ensconced in her cavity nest, bar a few short breaks to feed, drink and toilet herself. During this vigil she will sit tight, and as many generations of young egg collectors and bird ringers can attest, the nickname ‘Billy Biter’ is well deserved. Despite her devotion, it’s thought as many as a third of all Blue Tit clutches are predated by Wood Mice, Great Spotted Woodpeckers and Grey Squirrels. While the female incubates, the male has relatively little to keep him busy apart from feeding himself, and with his paternity already assured he will not feel the need to regularly sing during this period. He will, however, remain in sight of the nest entrance for the duration, and often escort the female on the occasions she briefly needs to leave the nest.
In contrast to the large Blue Tit clutch, no pair of Puffins has ever been recorded laying anything other than just a single egg. Despite a difference between years and a natural variation between colonies, early May, in most years, will be the peak egg laying period. The whitish-coloured egg, weighs in at over 60g or around 15% of her body weight. Unlike the eggs of Guillemots and Razorbills, which are pear-shaped to help prevent them being accidentally knocked or blown off their precarious nesting ledges, the Puffins’ underground egg need only be elliptical. After it has been laid, both members of the pair will take it in turn to incubate the egg, which is tucked against the bare skin of one of the brood patches located underneath each wing. Incubating in shifts, each stint will often last more than a day while the other partner feeds out at sea. Taking an average of 41 days, Puffin incubation is such a time-consuming affair that it won’t be until mid-June that the first Puffins will be seen coming ashore with fish, a sure-fire sign that their egg has transformed into a newly hatched underground ‘puffling’.
Close on the heels of the Puffins, those Nightingale pairs already established will begin nest-building in early May. The female, accompanied by the male, tends to select the precise spot to rear the young which is usually located on or near the ground, surrounded by dense vegetation and often underneath some shrubby growth. The construction duties are also her responsibility, as she starts by moulding a loose, bulky cup of dead leaves and grass, before then lining it with finer grasses and hair. The nest complete, she will begin laying her clutch of olive-green to olive-brown lightly speckled eggs, only commencing incubation when the last of the four or five eggs is produced. As the whole incubation process rarely takes more than 13 or 14 days, this means productive Nightingale sites should be awash with hungry baby chicks well before the end of the month.
For any Swallow pairs choosing to build a nest from scratch the assembly period may take around a week, and sometimes even longer when unseasonably cold or dry weather makes suitable mud harder to find. Variable amounts of dry grass, straw and even horsehair are all added to strengthen the cup, which is principally made up of over 1,000 pellets of mud that have been collected from a variety of suitable locations nearby. Built by both birds, the first stage of the process tends to be the construction of a ledge on which the birds can perch, and from this base they can then build the walls upwards and outwards. Only spending a few seconds on the ground as they collect mud from a nearby stream’s edge or hoof-print of a domestic animal, the mud is pushed into place using the bill and tongue, with the Swallow additionally vibrating its head up and down to ensure it is tamped down into place.
Most building takes place in the morning, which will allow the mud to dry well before nightfall and also free up the pair to feed during the warmest part of the day when insects will be most abundant. Once the external structure is around 20cm wide and 10cm high, comprising a cup deep enough to hold the chicks, the pair will trun their attentions to the interior soft furnishings. Lining the cup with dry grass, soft hair and white chicken feathers, no doubt collected from around the farmyard, the feathers in particular are much more than just a fashion accessory and will help to insulate the nest during incubation and prevent the eggs chilling too quickly in the brief moments that the female must leave for a stretch and a feed.
Mid-May
Totally absent during the egg-laying and rearing process, the male Cuckoo’s success must be measured not just by the number of matings with females, but also by his ability to keep any other competing males at bay in order to ensure his paternity. Upon arriving back at their regular breeding sites, the females will initially be keen to avoid the males, as more pressing issues will need to be addressed first, such as feeding up, and carrying out an assessment as to the state of the host nests in which they will ultimately hope to deposit their eggs. As it appears the best places for host nests are not always the best locations for caterpillars, most Cuckoos are thought to forage away from their breeding ranges. This means both sexes will have to periodically and temporarily suspend any breeding activities while away feeding in nearby locations, such as orchards with a rich supply of caterpillars.
While needing to be in the best possible condition to produce her eggs, some females must be careful not to delay the breeding process any more than
is absolutely necessary, as late arrival to the party may have already resulted in them missing opportunities to parasitise the first clutches of resident breeding birds such as Dunnocks, Robins, Meadow Pipits and Pied Wagtails. However, for those Cuckoos that have evolved to specifically victimise Reed Warblers, the need to lay quickly may be less of an issue, as Reed Warblers, like the Cuckoos, are summer visitors, meaning they will invariably be laying their first clutch later than the resident species.
Once the female Cuckoo’s initial assessment of the state of the surrounding host nests has been completed, she will then be in a position to succumb to the male’s overtures. Picking up on this sudden interest, the male will respond by singing excitedly, while displaying with a bowed posture, his wings drooped and his tail held, half-erect and fanned, to expose the white tips and notches. He may also rotate his body and swivel the fanned tail, as the female quietly watches – no doubt assessing his calibre. Astonishingly for a bird that doesn’t make a nest, the male will often fly down and even offer her a piece of grass, leaf or twig, but courtship feeding is only believed to occur very occasionally. After the relationship is consummated, the female’s next job is to continue her watching brief, as she quietly sits in any bushes or trees that afford discreet views of any host nests she may have already earmarked for an egg.
The fact that each female Cuckoo specialises on a certain host species was first discovered by the pioneering work of Edgar Chance on a Worcestershire common between 1918 and 1925. Chance noted that each Cuckoo egg tended to look remarkably similar to those of its chosen host species, and only ever appeared during the host’s laying period and, crucially, before the completed clutch meant incubation had already begun. As each host is deemed suitable for parasitism for such a small window of time, consisting of no more than three or four days, Chance realised that the female Cuckoo must watch her victims very closely in order to get her timings right. He subsequently discovered that the eggs are laid into different host nests at two-day intervals, with the crime always perpetrated in the afternoon or early evening. This interval not only gives the female Cuckoo plenty of time to form another egg but also to locate her next nest, enabling the egg to be quickly introduced at the precise moment of her choosing, when the parent hosts are least likely to be present at the nest. Ideally the Cuckoo will try to lay into those nests containing only one or two eggs, to not only minimise the chance of her own egg being rejected by the host, but also to ensure that her chick hatches as early as possible, in turn making the Cuckoo chick’s job of ejecting the host’s own eggs or chicks much easier.