by Mike Dilger
The couple may even undertake aerial transfers of prey, with the female leaving the building or cliff, and either catching the dropped prey in mid-air, or even more impressively, flying up below him before flipping over so that he can transfer the food from his talons to hers. With the pair now roosting together constantly, they will also frequently display to one another, particularly when close to the site chosen for egg laying. These ledge displays involve either the male or female, or even both, noisily bowing to one another in subtly different ways, which seems to vary from passive one moment to aggressive the next. After a time the pair will then graduate on to a level that can almost seem ‘affectionate’, as they engage in billing and gentle nibbling while producing their characteristic ‘ee-chupping’ calls, reminiscent of a Herring Gull with a sore throat.
With Tawny Owls being the first of our chosen twelve to begin their clutch, the male will now be stepping up his courtship feeding duties to ensure the female acquires the necessary condition to come up with the goods. For those Tawny pairs largely dependent on small mammals, which often tend to be cyclical in population, if it’s a ‘bust’ year then these owls may at this stage decide to abort the breeding attempt, preferring instead to hang on for another year when hopefully rodent numbers will be ‘booming’ once more. However, if the population levels of Bank Voles and Wood Mice look promising early in the season, then the female should be well fed, indicating that her youngsters will be well provisioned inside the nest. Perhaps most crucially of all, a good mouse and vole year will also see plenty of food on offer as the young slowly teach themselves to hunt in the summer and autumn.
Certainly by late February, any male Robin that has not yet managed to secure a mate may well be in for a barren year, unless he gets a lucky break. With Robin pairs still doing their level best to ignore each other, a small number of females may even leave their new partners at this stage, and opt for a quick divorce by taking up with a neighbouring male, or one even further away. Even though polygyny has been occasionally reported in Robins, where two females have separate territories as the male switches between both, monogamy is generally the order of the day. Experienced and established pairs will hope to raise a minimum of two broods during a good year, but with temperatures still depressed, and invertebrates – or chick food – still thin on the ground, there will still be no immediate hurry for the Robins to get down to the business of nest building just yet. After the male has gained a female his song quickly drops in intensity, and he will remain in this ‘amber’ state unless he is either forced to pick a fight with an intruder or if his mate is lost, so by now most of the Robin song heard should be coming from unpaired males. This behaviour doesn’t just occur with Robins but also American Song Sparrows, leading the American ornithologist Margaret Nice to write: ‘I often say to myself on nearing a territory where silence reigns overnight, such and such a male must be either dead or married, and upon careful searching I either find two birds or none.’
For Blue Tits aiming to time their clutches to hatch at the precise moment that caterpillars are at their most abundant, like the Robins there is currently no need to rush headlong into nest construction. Now very much an item, during the periods when the male is not preoccupied with maintaining his territory, the pair will often feed together as they visit garden bird tables or hunt through the still bare twigs for food. It tends to be around now that the sexes, when together, are most easy to differentiate. The male is usually a little larger and the blues in his plumage are a deeper colour while the yellows tend to be a touch richer. Also, in good light the male’s crown, when raised, will take on a cobalt, iridescent sheen.
Still finishing their moult as they begin their epic migration, the Swallows will now be streaming out of South Africa on a broad front, hoping that if all goes according to plan, the south coast of England should loom into view in around five or six weeks’ time. Swallows tend to migrate in fairly small loose flocks, meaning that individual birds are able to hawk for insects en route. Feeding on the way means that, unlike many other migrating birds, they do not need to build up large fat reserves beforehand. However, they will not be flying with the fuel tank needle hovering just above empty, as deposits may well be needed for insurance should they hit any adverse weather conditions along the way. Also, reserves will be essential when crossing inhospitable areas, such as the Sahara Desert or Mediterranean Sea. Catching insect prey as they go means that the Swallows will need to travel mainly during the day, rather than at night, with migrating birds mostly seen anywhere up to 18 metres above the ground. While on the move, they seem to prefer flying into a headwind or crosswind, which makes it easier for the birds to hunt low down without fear of stalling in mid-air.
On a good day they are believed to cover anywhere between 200 and 300km, and will try to find good roosting sites like reedbeds or dense grasslands each evening to lay up before starting out again early the following morning. Thought to travel in a north- to north-westerly direction as they leave South African airspace, late February should see our British Swallows moving through Namibia and Botswana and over the peculiar panhandle of the Namibian Caprivi Strip as they press on into Angola and Western Zambia.
With the Congo Basin still ahead of our Swallows, most British Cuckoos will still be in the Congo towards the end of February, with the majority of satellite transmitter readings centred around the mighty Congo River. The time at which they too decide to leave their wintering grounds will be quickly approaching, but unlike the ‘feed on the wing’ technique of the Swallows, the Cuckoos will carry out their spring migration back to Britain in a series of long-distance hops, with clear breaks to rest and feed up in between. With their departure imminent, the Cuckoos will almost certainly be trying to eat well and rest as much as possible before their first leg, which will see them travel anywhere from 500km to 2,000km in a northwesterly direction away from the Congolian swamp forests.
With the Cuckoos on the verge of leaving, most adult Puffins will be steadily working their way back to their natal colonies by late February. When airborne, the Puffin is thought to be able to cruise at around 58km per hour, and so could theoretically travel long distances quite rapidly. But with their short wings needing to beat at a frankly astonishing 400 beats a minute to keep the bird airborne, the energy demands this places upon them would require them having to regularly pitch down on the sea to replenish their reserves before carrying on. As the waters around most British puffinries won’t see Puffins in any large numbers before at least the middle of March, this would suggest that arriving at their breeding grounds in good condition is distinctly more important than arriving back early.
Returning too early to their north Russian breeding grounds would simply mean that the Bewick’s Swans would be unable to eat, because their breeding grounds on the maritime tundra would still be covered with snow, as well as the adjacent coastal waters probably still being frozen. Nevertheless, with the swans needing to make at least a couple of substantial refuelling stopovers before reaching the tundra, late February will see the majority of birds leave sites such as WWT Slimbridge as they conduct the first leg of their journey to the continent. The birds don’t all tend to leave in one flock, but numbers will fall away as the month progresses, with a few key nights seeing large numbers leave together.
James Lees, one of the WWT wardens at Slimbridge, has been lucky enough to see a few large departures over the years, and says that a few days before the swans depart they become decidedly nervous at feeding time. They will also spend substantial parts of the day sleeping, no doubt to conserve energy for the flight to come. The majority of the swans will only leave when the conditions are right - favouring dark, clear nights with plenty of stars to aid in navigation and a westerly wind to help push them in the right direction. When the precise moment for departure comes, it is usually preceded by the birds becoming incredibly vocal, with a huge amount of head bobbing. Only when the noise level and degree of synchronised head bobbing reaches fever pi
tch will the flock rise from the roost, before spiralling into the air to quite a height, in order to gain their bearings, as they head off for the continent.
In a good Waxwing year, the number of birds in Britain by now may well have declined from the peak seen at the turn of the year. However, late February may well still see these gentle marauders dispersed far and wide as they track down the few remaining supplies not already mopped up by the resident Blackbirds, Song Thrushes, Mistle Thrushes or the combined total of around 1.5 million Redwings and Fieldfares also visiting Britain for the winter. Even in a year when relatively few Waxwings cross the North Sea, the east coast at this time will almost certainly see a smattering of flocks visiting any garden with berries going to spare. Always approachable, probably due to the lack of human interference on their breeding grounds, the Waxwings will still be in no hurry to leave.
Out of our four summer visitors, the only species that has seemingly not even entertained thoughts of leaving come the end of this month is the Nightingale. Recent data collected from the BTO’s research work suggests that the birds will not leave until mid-March. But by feeding well in West Africa, once the Nightingales finally do decide to leave, the first leg will see them power to southern Europe with all possible haste.
March
Even if the weather conditions seem to say otherwise, higher daily temperatures and a few precious minutes of daylight clawed back with each passing day can only mean spring has most definitely sprung by March. As a yellow army of Daffodils, Primroses and Lesser Celandines begin to appear and overwintering butterflies and queen bumblebees tentatively emerge, many of our winter visitors will take the improving conditions here as their cue to desert our shores for long, arduous journeys to far-flung locations. The noisy and extensive dawn chorus here in March, however, is ample demonstration that this month has already become a hectic time for our resident British birds. For any individuals that successfully negotiated the winter, their reward will have already come as they find themselves either on or close to their breeding grounds, putting them in pole position to race ahead in the mating game. However with most summer migrants well on their way, the resident birds will be only too aware that they won’t have our gardens, woodlands, farmland, scrub and wetlands all to themselves for long! Despite many of our summer visitors still being thousands of kilometres from Britain, the traditional advance party of Wheatears, Sand Martins and Chiffchaffs will have already begun to arrive at many southern migration watchpoints during this month. In fact, this initial trickle will soon turn into a ranging torrent as millions of birds head towards Britain to take advantage of our green and pleasant lands.
Early March
The first of our chosen twelve to kick-start the egg-laying season will be the Tawny Owls. Being a cavity-nesting bird, the female Tawny doesn’t need to produce a camouflaged clutch, and so her rather round eggs are white and unmarked. Before laying each egg the female tends to become distracted, and using her bill to grasp on to the walls of the nesting chamber, the egg will often be delivered while standing up. Tawny Owl expert Dave Culley has spent many sleepless nights waiting for his wild Tawnies to produce their clutch, and reckons the female will lay an egg every 56 to 64 hours, with sometimes a delay of up to four days before the final egg is produced. Clutch sizes can vary, but two or three is considered the norm, with some pairs capable of producing four or even very occasionally five. The time-consuming matter of incubating the clutch is carried out by the female alone, and from Dave’s studies, he reckons she will only properly begin sitting with the penultimate egg. In preparation for the ‘big sit’ she will also pluck out her breast feathers to reveal the brood patch, a bare area of skin well supplied with blood vessels at the surface, making it possible to easily transfer heat to the eggs. If she has to leave the clutch for any reason before proper incubation commences then she will cover the eggs over. From the point incubation begins she will suddenly become utterly reliant on the male provisioning her with food during this period of solitary confinement.
Only marginally behind our Tawny Owls in the laying stakes will be the Peregrines. At this stage, the male will be taking full advantage of his conjugal ‘rights’ by copulating with his mate as frequently as possible. Most female Peregrines are substantially larger than their partners, so the male needs to be careful to telegraph when he’d like to mount her, to ensure his actions are not misconstrued as aggressive. Stating his intention involves a ritualised hitching of his wings, making it look just like he’s shrugging his shoulders and can sometimes be accompanied by the male prancing around as if on tiptoe. If the female is agreeable to his overtures, she will then lean forward, and swing her tail to one side, inviting him to jump on. Resting his tarsi on her back and with his talons curled into a ball to make sure he doesn’t harm her, he will then press his tail under hers. Constantly flapping his wings to maintain balance and ensure he doesn’t slip off, the entire mating deed will often take less than ten seconds. This briefest of liaisons also tends to be conducted amid a cacophony of noise from both the birds.
Despite moments when they’re still a touch uneasy with one another, many pairs of Kingfishers should by now be fairly established and settled for the oncoming breeding season. Once a partner has been secured, the first priority for the newly engaged couple will involve choosing the appropriate bank in which to excavate a nest. Kingfisher nests are always situated in an enlarged chamber at the end of a narrow tunnel, and unless the pair decides to refurbish an existing ‘second-hand’ nest, they will dig a fresh one. An ideal nest site should be easy to excavate, yet safe from both predators and flooding. Most sites chosen tend to be in vertical, steep or overhanging banks on the edge of the watercourse, and are often sited both at least a metre above the water and 50cm or less below the top of the bank. Crucially, the location must also be within the birds’ territory. Soft or sandy soils with few roots and stones will make the digging more straightforward.
Excavating the tunnel and chamber is generally a shared task, but the males will do the lion’s share of the digging. The hole is initiated by the male flying at the bank with his bill extended, while his mate watches from close by. The moment a foothold has been created, the Kingfisher is able to enact an impression of a woodpecker, as he wields his bill like a pickaxe while hanging on to the bank. During the whole tunnelling process, the pair often work in shifts, with the non-digging bird on the lookout for both intruding Kingfishers and possible predators. Most of the digging tends to be carried out in the morning, and as the tunnel gets longer, the process seems to become easier. The digging bird will use its feet to push the soil behind it, and as the tunnel measures little more than 5 or 6cm across, it then has to reverse out, using its tail feathers as a mini-bulldozer to clear out the spoil. The tunnel leading to the nest chamber is usually around 45 to 90cm long and dug either on a slight incline or in horizontal fashion, and only when work starts on the actual nest chamber will the birds finally be able to turn around inside and emerge from the tunnel bill first. Depending on how hard the soil is, and whether any obstructions are encountered along the way, the whole process may take between a week and 12 days.
In contrast to the engineering feat that is a Kingfisher’s nest, Lapwing nests consist of little more than a scrape in the ground. This arguably gives the males far more time to perfect their wonderful flight displays to both impress any as yet unpaired females, and to warn any neighbouring males against trespassing. As many Lapwings choose to nest in ‘loose colonies’, polygyny is considered quite common, with one study in Teesdale, County Durham revealing that between 20 and 44% of males had been successful in securing two or even three mates. Those males with two or more females often tend to be more experienced, and so have larger and better quality territories more capable of rearing multiple broods simultaneously. It’s also thought that many females may ignore the younger males, preferring instead to playing second fiddle to an already mated male. This mating system inevitably means there will be a num
ber of males, holding possibly peripheral and inferior territories, which may miss out on a mate entirely. For these birds, the breeding season may well then be downgraded to a watching and learning brief, with the hope that any experience banked will count in their favour in future years.
At this stage, neither Robins nor Blue Tits will have advanced their breeding season any further than establishing a territory and attracting a mate. As invertebrate prey is still low in abundance at this time of year, and with incubation only taking around a couple of weeks, both species are in no hurry to press forward come early March. The male Robin, having secured his mate, is still doing his level best to ignore her, and when not feeding, the vast majority of his time will still be taken up by singing and fighting. Despite their territorial nature, Robins will frequently enter neighbouring territories, particularly in search of food. These trespassing Robins will rarely sing or display and try to remain as inconspicuous as possible, being only too aware that if spotted they will need to beat a hasty retreat. With the incumbent male winning the majority of his battles, the only Robin left entirely in peace within the territory will be his mate, whom he should by now be able to recognise from quite a distance. While not as strongly territorial as the Robin, the male Blue Tit will still be clearly demarcating his territory through singing and aggressive behaviour towards any intruding males. Their pair bond, which formed in winter, will also continue to be cemented with nest building now just a few weeks away.
