Nightingales in November (14 page)

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 number 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.

By early March most Bewick's Swans will have left Britain for the near continent on the first leg of their epic spring migration. Flying at speeds of between 46 and 70km per hour, depending on the prevailing weather conditions, they are not thought to fly at particularly high altitudes when migrating. It is also assumed that individual birds or family parties may well use the same staging sites each year where possible, with several locations being incredibly important for refuelling along the way. It has been calculated from energetic studies that large birds like Bewick's Swans may only be able to fly an estimated 1,500km before needing to refuel for the next stage of their journey. Because the breeding sites are 3,000 to 3,500km away, the swans are thought to make at least a couple of stops during spring migration, and possibly even more if they encounter severe weather conditions along the way, or the adults are still accompanied by their offspring.

Satellite tracking of Bewick's Swans has recently been initiated by scientists at the WWT. Eighteen swans were caught between 2012 and 2014 at Slimbridge and the Ouse Washes to have transmitters attached in the form of collars around their necks. Already the data the swans are sending back to the team is revelatory, proving that upon leaving
Britain, the majority of tagged birds immediately relocate to Denmark. This research has also revealed that a proportion of these tagged birds (and therefore presumably a proportion of the population), will then continue either south and inland, into Germany, or further east into Poland. It's thought the birds staying in Denmark may well be feeding in agricultural fields, such as maize stubble, in contrast to the birds visiting Germany that are feeding in wetlands, swans in Poland which have been seen feeding around fish ponds.