“Among the excitements that have helped to keep Dublin alive this past winter, quite a prominent place must be given to the spectacle afforded every night of some hundreds of pied wagtails assembling to roost on a small tree in the very centre of the city...”
Their chosen perch, as CB Moffat reported in the Irish Naturalists’ Journal, was a small plane tree “in the brightly-lighted middle of Sackville Street – now commonly, though not legally, called ‘O’Connell Street’ – and so stationed that the electric trams going up and down the street until nearly 12 at night pass with noisy signals almost within touch of the tree, and at both sides of it, at the average rate of rather more than two to the minute”.
The trams set the scene in 1929, when Moffat was a Daily Express reporter, if of a modest sort. His naturalíst passions and bird-like demeanour earned him gentle mockery in the newsroom. His colleagues, according to one of them, would not have been surprised “if Moffat flew in and lighted on the gas bracket”.
He was, nonetheless, in the judgment of Robert Lloyd Praeger, "the most brilliant naturalist – in the Gilbert White sense – that Ireland has produced". And his watch on the Dublin wagtails continued when the birds returned the following autumn. Their numbers built up to close on 600 and nightly crowds began to build around a tree as its bare upper branches looked to be "covered with silver leaves".
At about 30 minutes after sunset the birds began dropping down from every point of a deepening blue sky like bees flying home to a hive
In the winter of 1931-32 the roost numbered well over 1,000 birds, some of which stayed on until July, even through the crowds and bands and flag-waving of the Eucharistic Congress. By 1934 they had doubled and spread into a second tree, becoming, as Moffat said, “a distinct asset to the city [and] they never receive the slightest molestation”.
Through the following decades, successive generations came to roost, changing their trees from time to time and varying in mid-winter numbers to more than 3,500.
In 1982, on a Christmas shopping trip to Dublin, I went to O'Connell Street with David Cabot, an ornithologist friend, to see the wagtails fly in at dusk. It was an unexpectedly exhilarating sight. At about 30 minutes after sunset the birds began dropping down from every point of a deepening blue sky like bees flying home to a hive.
In the last two trees near the Parnell Monument they alighted in twigs above the Christmas fairy lights, moving restlessly among the dark, round bobbles of the plane tree fruits and twittering a vigorous evensong. There were, perhaps, around 1,000 birds and their twittering was vigorous enough to carry above the traffic. But within an hour they were still. (My drawing, made in black and white for the column, offers only an indicative dozen.)
Among the fuller counts were some made from the top of Nelson’s Column, and the exceptional and regular roosts generated several scientific studies. A Trinity geographer found that the temperature in O’Connell Street on a winter night could be as much as two degrees higher than in the surrounding countryside, and that the centre of the street was warmer than the ends.
The three trees just north of the GPO were, therefore, where the wagtails concentrated in the coldest weather, spreading out more widely when it got milder. The ornithologist Tom Cooney saw wagtails fly into the Corporation Christmas tree on especially bitter nights, seeking denser cover and the extra warmth of the bulbs.
The birds have also long discovered the virtues of glass for keeping warm, roosting on or under glass roofs in sheltered places across both islands. Roosts in commercial greenhouses have sometimes made a terrible mess of carnations and tomatoes.
Nelson’s Column was blown up in 1966 and, many years later, replaced by the Spire in the civic “regeneration” of O’Connell Street. The felling of the plane trees was planned in 1998 and began in 2002 amid public protest (not, that I can find, very much in defence of the wagtails’ winter roosts). Some 40 mature trees, officially reckoned to be hiding the street’s facades and spacious scale, were replaced by more biddable and geometrically “pleached” limes.
At what point the wagtails dispersed and exactly where they went seems to have escaped the record. Last March, however, a 12-year-old reader in Dún Laoghaire told “Eye on Nature” of “hundreds” of pied wagtails flying in at dusk to roost in bamboos in a water feature at the new library building. That, at least, echoes their retreat to reed beds and thickets in the countryside.
