Remember to look up this Christmas to enjoy gangs of ‘pied wags’ gathered in the trees
ROOSTING PIED WAGTAILS
0ne of the most joyous and time-honoured festive traditions for many this month must surely be decorating the Christmas tree. But while adorning the tree in the warmth of your homes, do spare a thought for the feathery baubles festooning a number of urban trees outdoors, as pied wagtails join forces each dusk to collectively see out the long, cold winter nights.
Identified by their monochromatic plumage, jerky walk and habit of constantly pumping their long tails, pied wagtails are without doubt one of the most beloved members of our wonderfully diverse avifauna. Breeding across most of Britain, these adaptable little birds are often, but not always, close to water and tend to prefer ‘open country’ in farmland, moorland and even town parks. Insectivorous by nature, their favoured food is taken from the ground, the water’s surface or snatched midair. Flies, midges and caterpillars are popular meals.
Our ‘pied wags’ are considered a race of the white wagtails found in mainland Europe and most are resident here all year round. However, ringing data suggests that those breeding in Britain’s northern uplands are forced to southern England and Ireland as autumn proceeds, while some fair-weather wags will even opt for a spot of winter sun in southern Europe.
Winter also sees a behavioural change, as the wagtails abandon their strategy of hanging out in ones and twos in the countryside and instead form communal roosts in our urban centres. Certainly, the ability of human-made structures, such as roads and buildings, to absorb and retain heat better than grassland or woodland in winter results in a phenomenon known as the ‘urban heat island effect’. So pronounced is this that winter temperatures in London, for example, can be up to 10°C higher than in the surrounding countryside. When this is combined with the relative paucity of predators found wherever humans gather in any number, it’s not difficult to work out why pied wagtails find the bright lights and busiest thoroughfares in cities such an attractive proposition.
It’s also now broadly accepted that the birds use this ‘coming together’ as an opportunity for information exchange. Essentially, those birds that have struggled to find enough food during the day can follow any better-fed individuals to richer feeding grounds the following morning.
