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Thursday 18 July 2019

Ireland a Leisler's Bat stronghold

Leisler's Bat.
Leisler's Bat.

Fresh droppings on the ground under the exit hole from the roost evidenced that the bats were in residence in the attic space. I sat and listened to a Song Thrush singing while I waited for the bats to emerge.

The bats in the roost were Leisler's Bat the largest species of bat we have in Ireland. They are native here and while they are reported to be widespread throughout mainland Europe they are generally scarce everywhere except here making Ireland the global stronghold of the species.

My task was to count the bats. Those in the attic comprised a maternity roost, an exclusively female collection of nursing mothers each suckling her single new-born pup. Adult males roost separately. The mothers would soon leave en masse, feed themselves quickly and return to the roost to suckle and tend their pups.

Leisler's Bats are the earliest to emerge among Irish bats. They fly at, or slightly before, sunset. The lactating females all leave together flying high and fast from the roost to cattle pastures where they hunt their favourite prey items: Yellow Dung Flies, Dung Beetles and midges associated with cow pats.

As I waited in the gathering dusk on a lovely summer evening several small flocks of Rooks passed purposefully overhead heading homeward. Lines from Macbeth came to mind. While leaving aside Shakespeare's intended symbolism and though taking the two lines out of context, the bard's wonderful words nevertheless seemed particularly apt as a description of the moment: "Light thickens, and the crow / Makes wing to th' rooky wood."

The first bat exploded from the exit hole bringing me back to reality. Others followed fast and furious each animal leaping from the exit at the apex of the gable and dropping momentarily before powering away with strong and rapid wing beats. Once airborne they echolocated loudly their staccato calls registering at a peak frequency of 26kHz on my bat detector.

By 10:30pm all of the bats had flown, most birds had gone to roost and the world had fallen quite. The Moon was growing brighter as the daylight faded. A flock of late-flying gulls passed overhead flying lazily at height towards the coast silhouetted against the darkening sky.

As I packed up to go home the Song Thrush was still repeating the same group of squeaky notes that it had started with; its voice the last remaining one to be heard in the dusk chorus.

Gorey Guardian

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