Nightingales in November (25 page)

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.