by Mike Dilger
The fact that we derive enjoyment from listening to the bird’s song is entirely incidental, as like all bird song, it is only ever produced for the ears of its own species, having evolved as a tool to both repel competing males while simultaneously drawing in the females. Commonly, male Nightingales will arrive back a touch earlier than the females, and as they jockey for position at sites they’ll be familiar with from previous seasons, it will be the ‘repel’ element of their song that is initially deployed. The main concentration of breeding Nightingales in Britain runs in a broad band through the counties of Suffolk, Essex, Kent and Sussex and each male holding a territory will be desperately keen to ensure that his trip all the way back from West Africa won’t have been a wasted one.
While not a patch on the vocal ability of the Nightingale, with its undoubted talents lying principally in its migratory feats, the Swallow’s song nevertheless also plays an important part in securing a mate for the breeding season. Like male Nightingales, the first Swallows to arrive at their traditional breeding sites will usually be the older males, who will then quickly proceed to lay claim to a breeding site of little more than a few square metres, but which crucially contains either a nest or a potential nest site. Once this miniature territory has been secured, the male will then chase away any other males showing any interest in his location and back up this ownership with song and display. His song is a not unpleasant and rapid twittering, which often ends in a harsh rattle and the subtle variations within are thought to convey important information about the bird’s age (or his experience) and his health (or attractiveness). The male’s tail also plays an important part in securing a site and attracting a partner, and so during these early stages of the breeding season will frequently be spread wide to reveal the striking pattern of white spots.
Once a bird that nested in caves before humans began to construct their own accommodation, many Swallows have nowadays opted for rural buildings as nest sites, with farmyard barns and cattle stalls amongst their favourite locations. The substrate to attach the mud nest to needs to be suitably rough, so cracks, corners or any type of fixing will all help secure the nest if no horizontal support, such as a beam, is available. Nest sites will also need a clear flight path for safe and rapid access and exit, and nests also tend to be sited at locations to protect the chicks from bad weather and against any variety of predators.
In terms of their breeding patterns, Swallows can be considered similar to Lapwings, in that they usually breed either solitarily or in loose, social groups. For those birds that have taken the gregarious option the territories and nests are never immediately adjacent to one another, as is the case with Sand Martins nesting cheek-by-jowl in a sandbank, but instead have a large degree of separation. For example, different Swallows will frequently hold territories in separate outhouses of the same farm, or at the very least at the opposite ends of a large barn, where an informal arrangement seems to be made which ensures that the nests are out of a direct line-of-sight with each other.
As the male Swallows begin to nail down territories in anticipation of the arrival of the females, the male Cuckoos will still be short of their final destinations in Britain. It seems the case that both the route taken back from Africa and the prevailing climate at this time of year will have a huge impact on the Cuckoos’ progress as they work towards their breeding grounds. Take Chris, for example, which is still the only Cuckoo to be followed by satellite over three separate springs on his way back to Britain. In 2012, come the middle of April he was thought to be held up by poor weather in north-west Italy, while in 2013 he was in northern France close to the border with Belgium by this time, with spring 2014 seeing him in central Spain, having possibly been delayed crossing the Sahara.
With the returning Cuckoos spread in a wide European arc as they close in on Britain, mid-April at many puffinries will be the time for established couples to conduct a quick spring clean of their previously used burrows, with egg laying just a couple of weeks away. Most burrows will at some point have been constructed by the Puffins themselves, although on Skomer Island off west Wales, pairs without a burrow have been known to misappropriate Rabbit or Manx Shearwater burrows for their own use. Typically a touch longer than the human arm, the ideal burrow is usually situated on a 20–40° slope with the opening facing out to sea. This entrance will then form a narrow, blind alley dug through the soil or peat that ends in a slightly elevated and wider nest chamber. In favoured nesting sites these burrows can be at such high densities that there may only be a few centimetres of ‘wall’ separating some of the burrows. In a flourishing puffinry, any newly formed pairs or evicted couples may well have to start digging a new home from scratch. Excavation and restoration is carried out by both birds, with the male thought to carry out the largest share of the workload as he uses a combination of bill and feet to dig down into the peat or soil.
Compared to Guillemot and Razorbill colonies, which are deafeningly noisy, puffinries are generally much quieter places. Once members of a pair are together in their underground burrow the occasional groan can be heard, but recordings made with sensitive microphones show that in fact a whole range of vocal activity below our audible range frequently takes place just under our feet. In addition to preparing the burrow, this is also an important time for Puffin pairs both to demonstrate their bond to one another and declare site ownership. The most frequent demonstration of ‘married status’ to neighbouring Puffins is when a pair engage in ‘billing’. This bill-clacking behaviour usually happens when a puffin lands by its mate either at a club or the burrow. This billing can quickly become an infectious activity as surrounding pairs copy the behaviour and spread the love like a Mexican wave! Individuals will also ‘spot stomp’ around their burrow, a ritualised behaviour that involves raising and lowering alternate feet with their webs spread, while remaining on one spot – which in the world of the Puffin simply says ‘This is mine, all mine!’
As Puffins re-familiarise themselves with their burrows, it seems that the Bewick’s Swans will also be reacquainting themselves with well-known and previously visited stopover sites across Estonia and Latvia during much of April. With the Russian Arctic still almost certainly frozen over in this month, it seems that the spring migration for Bewick’s Swans back up north is a leisurely affair taking anywhere between eight and ten weeks. This contrasts with their autumn migration to Britain which has been calculated as only taking between four and six weeks, as the rapidly plummeting temperatures and shorter days combine to play a large part in forcing their movement towards the Gulf Stream-warmed countries of Britain and the Netherlands. During this period of the year, Eileen Rees from the Bewick’s Swan research team at the WWT thinks that around three-quarters of the population of swans from the European or north-west flyway may well be widely dispersed across Estonia’s wetlands. In addition to important coastal sites such as Matsalu Bay and Pärnu, where the swans will be principally feeding on pondweed, they may also be taking advantage of any ice-free floodplains and agricultural areas further inland, while waiting for the ice to retreat further north.
As Waxwings also continue their migration north with winter slowly beginning to relent, April may well see a gradual change in their diet. Having force-fed themselves on little other than berries for over six months, the first warm days of spring will see an emergence of swarms of insects – a vital source of some much-needed protein for the birds. Keen to take full advantage of any good feeding opportunities that arise along the way, the Waxwings’ technique of catching insects, as they sally to and fro from open perches, will see them plucking any midges and mosquitoes straight from the air.
Back at the Tawny Owl nest, the young chicks appear to spend large parts of the day sleeping, and on the few occasions when the female needs to leave the nest to defecate or cast pellets, they will often huddle together to reduce heat loss. However, within a week of hatching, the scanty down they were born with will quickly become a far more plentiful covering. Feeding als
o becomes easier for the chicks once their eyes start to open after around 12 days, enabling them to take far more initiative in begging for prey items brought into the nest. Unlike the chicks of Robins and Blue Tits, for example, the small owlets don’t produce their faeces in neat sacs, so their excrement is often simply eaten by the female. If the male is providing plenty of food at this stage, any uneaten remains in the nest can quickly build up, attracting flies, and so the brooding female will also have to make sure that the young chicks are regularly preened to keep them as clean and healthy as possible during this period of incarceration.
Requiring around two weeks less incubation time than the 28 to 30 days needed by the Tawny Owl, female Robins – certainly in southern Britain – will see their first chicks emerging with late April approaching. As soon as the chicks hatch, the female’s first action is to remove the now redundant eggshell from the nest – part of which may be eaten if she is calcium deficient. The chicks are looked after by both parents, but the female’s brief, certainly for the first few days, will be to brood them. Hatching naked, they’re unable to maintain their own body temperature and will quickly die from being chilled if exposed to any April showers at this sensitive stage. During these early days, if the male brings back food while his mate is brooding he will pass it directly to her to feed the chicks. Fed on a high-protein diet of spiders, beetles and worms, the young grow incredibly quickly and will rarely spend more than two weeks in the nest before starting to fledge.
Despite laying well before the Robins, the Peregrines’ lengthier incubation means that among those clutches laid around mid-March, the chicks should only now be entering their final stages of development before the egg tooth is deployed. As the female is charged with carrying out most of the brooding, the male’s role will still be to provide the lion’s share of food to keep both parents-to-be well fed.
Certainly in the case of urban-nesting Peregrines, feral pigeons are the most common food items consumed throughout the year, but as spring develops, Peregrine expert Ed Drewitt has found some fascinating changes in their diet. By analysing feathers collected at well-known urban nest-sites, he’s been able to identify a whole variety of spring migrants caught and killed such as Wheatears, Turtle Doves, Nightjars and even the occasional Corncrake. Confined to rural farming locations in north-west Scotland, the British breeding population of the shy and retiring Corncrake is thought not to number any more than 1,200 pairs and it’s patently obvious that these urban Peregrines have no respect for rarity when catching this member of the rail family during its migration north. Many of these migrants would never normally have been associated with urban habitats, but thanks to the Peregrines’ opportunistic abilities, we’re now learning more about their migration routes. In many cases it seems these migrant birds are flying over some towns and cities, which they may be using effectively as way-markers en route to their summer residences elsewhere.
By mid-April, most Kingfisher and Lapwing pairs will be in full incubation mode. Protected by their tunnel fortress, predation levels of Kingfisher eggs are thought to be very low, but the clutch is still rarely left unattended for any length of time to ensure the eggs don’t chill. One disadvantage of nesting in almost total darkness, however, is that if an egg becomes separated from the rest of the clutch, possibly when being turned, then the adults don’t seem to notice, leaving it to a chilling fate. Unable to see the outside world, the sitting Kingfisher will also have to wait for a whistle from its partner to know when a changeover is due. Upon hearing the signal that the coast is clear, the previously sitting bird will emerge blinking into the daylight, giving it an opportunity to stretch, take a toilet beak and even catch a fish or two before sitting duties recommence.
By contrast, as Lapwings nest out in the open, any changeover between parents is far more easily coordinated, and so any egg accidentally dislodged can quickly be brought back into the fold. The main problem Lapwings have during incubation is preventing their eggs being either accidentally trampled on by cattle, or predated by anything from Carrion Crows and Stoats to Foxes and Badgers. Adult Lapwings can often deter any livestock from encroaching too close to their clutch by flashing open their wings in front of the cattle, but determined predators require a more concerted and coordinated effort. Carrion Crows are considered serious predators of eggs and will be mobbed severely by both parents if they approach the nest. Any Lapwings that have bred as part of a larger colony will often be able to collectively muster an aerial bombardment, enabling them to more effectively drive the crows right out of the territory. Mammalian predators, however, are a potentially very serious proposition, as they’re also capable of taking any unwary adults sitting on clutches. When faced with a Fox or Stoat, for example, the Lapwings’ main reaction is to circle above the predator while calling, which not only keeps both adults safe but also warns other birds of their presence, in turn making the nest more difficult to locate. Despite these techniques, some clutches are inevitably predated and so the Lapwing’s last line of defence is simply to quickly replace the lost eggs in a different nest.
Starting before the nest is finished, the female Blue Tit will proceed to lay an egg each morning until her clutch is complete. The eggs are white, with tiny reddish or chestnut speckles which are more densely concentrated at the blunter end, and weigh in at around 0.5g. The clutch size can vary enormously, between 5 and 16 eggs, although for the highest numbers there is the suspicion that maybe more than one female is laying in the same nest. Even so, Blue Tits lay some of the largest clutches of any songbirds, which fits in with their ‘all your eggs in one basket’ strategy. Younger females tend to lay smaller clutches, while those birds nesting in woodland often lay more eggs than those who have chosen farmland localities, who in turn will frequently have higher broods than any Blue Tits which plumped for a garden nest box. Despite gardens being incredibly important for keeping hungry birds fed during the cold winter months, when it comes to the breeding season, it seems that deciduous woodlands, with their huge spring concentrations of caterpillars, will always trump anything that any other habitat has to offer.
Late April
After around four weeks of constant incubation, the female Lapwing’s hard work will finally pay off as her clutch begins to hatch. Using their strong neck muscles and egg tooth, the chicks will break out by both bracing themselves against the inside of the egg while tapping away from inside to crack the exterior. Once the Lapwing chicks have recovered from their efforts and dried out sufficiently, their already advanced state of development means they’re able to run around and feed themselves almost immediately. The precocious chicks are delightful little creatures, with long blue-grey or pinkish-grey legs, a short dark bill and sandy-brown down, which is dotted and streaked black. They also have a very distinct white patch on the back of their neck, which stands out when the chicks are running around and almost certainly enables their parents to easily keep track of them. However, the instant they feel threatened, or in response to their parents’ alarm calls, they will crouch motionless with their legs drawn in and heads down in order to hide the white patch and melt into their surroundings. Not needed to find food for their young charges, the parents’ role is both to lead them to the good feeding areas and guard them from any marauding predators eager for an easy meal.
A mosaic of habitats seems to suit the chicks best, with wet patches and short swards for feeding, while also comprising longer, more rank vegetation for concealment should danger appear. Ideally these good feeding areas will be present within the parents’ territory, but if not, the adults will quickly corral their offspring away to other locations, possibly hundreds of metres away. As the chicks are unable to fly so soon after hatching, any impassable obstacles encountered on the way can usually be negotiated by the parents simply airlifting their chicks over to the other side. The feeding behaviour of the chicks seems most closely to resemble that of back-garden chickens, with the chicks scratching around the central figure of their mother while the
y search out beetles, larvae and earthworms. They also feed like their parents, by moving and scanning, with any chick straying too far instantly called back to the fold. Despite being able to find more than enough food themselves, they can initially struggle to keep warm during poor weather so will still disappear under their mother to be brooded on cold, wet days and each night.
For the few days before they eventually break free of their ovoid prison, the incarcerated Peregrine chicks will begin cheeping to their parents, who often respond, before becoming noticeably more restless as they prepare for the youngsters’ arrival. The chicks will usually emerge within the space of a couple of days, although not all eggs will necessarily hatch, as a small proportion tend to be either infertile or suffer from the embryo having died during incubation. After their exertions to break free the young will initially be weak, wet and exhausted, but then quickly dry out into fluffy, white chicks. Unlike the Lapwing youngsters, the Peregrine chicks hatch in a far less advanced (or altricial) state and so are utterly reliant on their parents for some months before they are able to catch their own food. Upon hatching, the parents don’t bother to remove the eggshells, which instead are trampled into the nest by the chicks and parents over time.
