Friday 27 April 2018

Country Matters: Keeping track of a feathered angel

Black screamer: Swift
Black screamer: Swift

Joe Kennedy

Swifts, 'devil birds' or 'feathered angels of the upper air' (as the poet John Heath-Stubbs described them), have returned to the burning shores of Africa by now.

A few stragglers may still be about but most of the several thousand birds that arrived here in May now will have departed. And details of a tracking-tagging project on the summer home-comers, undertaken last year by BirdWatch Ireland, the British Trust for Ornithology and the Northern Ireland Swift Group, are still under wraps, as is usual for scientific studies where careful analysis is paramount. Details are eagerly awaited.

Seven swifts were geo-tagged for a survey to learn more about their migration patterns in a first-time project The technology included light sensor, memory chip, clock and battery - all packed into a tag weighing 0.65gr, or about 2pc of a swift's bodyweight. This light-level geo-locator logged a bird's position each day, using sunrise and sunset to calculate longitude and latitude.

BirdWatch Sligo branch's Michael Casey told the nature charity's journal Wings that as the tags did not transmit data the project depended on their unhindered return so that the body chips could be downloaded.

The chosen birds were tagged at two colonies - one at Michael's home at Tubbercurry and the other at the Antrim nestboxes of Mark Smyth, of the North's Swift Group. Chris Hewson, of the British Trust, an expert on geo-tagging, supervised the Irish bird-ringers.

If you are a fan of these beautiful dawn-and-dusk sky screamers and would like to help in their survival you could consider placing suitable swift boxes in high eaves - if you live in an old house or have a business link with a warehouse or factory.

The purpose-built Schwegler boxes are expensive (up to €60 each), and it is also necessary to invest in swift-call CDs and see they are played at dawn and dusk daily for encouragement. However, as has happened in the North, commercial sponsorship may be found, such as Tesco at Crumlin, Co Antrim (an impressive 20-box nesting tower at the store) and Translink, the North's bus service, at a depot.

In recent times the birds have faced serious challenges seeking sites on newer buildings in their old areas. However, some sites remain and the birds return to convents, church buildings and warehouses.

Unlike their cousins, swallows and martins, swifts do not hold farewell assemblies on high wires. One evening the high-pitched shrieks may be heard overhead, the next, all is silence.

I have vivid memories of watching swifts in diverse places from Listowel to Tarragona in Catalonia, and them swooping over diners' heads at the walled town of St Paul de Vence in the Alps Maritimes.

The naturalist David Cabot reckons about 20,000 pairs of the gabhlan gaoite arrive each year. The black screamer, which snatches at scraps in mid-air to build its nest, is kin to the tropical humming-bird which can fly backwards, according to Heath-Stubbs.

Such data may not be expected to be found on the geo-tags, I am sure.

Sunday Independent

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