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Tuesday, 9 August 2016

GPS tracking of Kerry Barn Owls

Readers of this blog will be well aware of the impact that major roads have had on local Barn Owls with, for example, 14 Barn Owl casualties recorded on the 13.4km stretch of the Tralee Bypass in just two years. BirdWatch Ireland and Transport Infrastructure Ireland have been undertaking a two-year project to try to find out how and why Barn Owls might use or interact with these major roads, and ultimately to address how best to prevent and/or reduce such casualties in future.

Part of this project was to put GPS data loggers on individual owls to track their movements in incredible detail, and several of those owls have been tracked in Co. Kerry.

Adult Barn Owl ready to be released, with the GPS tag in place, July 2016 (M.O'Clery, under licence from NPWS).

The GPS data loggers capture the birds' position, height and speed every few seconds, showing exactly where the birds hunt, roost and rest. 

So, how have Barn Owls been interacting with the major roads in their home ranges? The findings so far have been striking. Have a close look at the image below, tracking part of the movement of a female Barn Owl whose nest in north Kerry is about 2km distant...

 The image above shows the tracking of a female Barn Owl hunting along the grass verges of the Tralee to Listowel road near Kilflyn, crossing the road three times in just a few minutes. Red dots show where the bird was stationary (perching/perch-hunting), orange is slow (hunting) flight, yellow is faster flight (J.Lusby/M.O'Clery, under licence from NPWS).

Of three Barn Owls tagged in Kerry so far, two had major roads in their home territory. In both these, the birds actively hunted for extended periods along the grassy verges of those major roads.

And in an even more striking example, the video below tracks the movements of a female Barn Owl from a nest site just outside Castleisland, Co. Kerry, in late July. The video starts with a view of her nest site, but we join her nearly 2km away, at a farmyard where she has been sheltering from torrential rain for four hours. It is now 1.30 a.m. and, as the rain finally lets up, off she goes. We can track her movements as she perches on trees and hedges and then, she arrives at the Castleisland Bypass...

Video showing the movements of a female Barn Owl along the Castleisland Bypass, Co. Kerry. The GPS device was scheduled to record one fix every five seconds - yellow fixes are where the bird was flying at speed, orange fixes indicate slower hunting flight and red is where the bird was stationary (J.Lusby/M.O'Clery, under licence from NPWS/BTO).
(You can click on the 'four arrows' symbol, bottom right, to see a full screen version of the video)

On one night she hunted along a 1km stretch of the Bypass for 55 minutes, crossed the road six times, and even perched on the central median for 17 seconds! The dangers to the Barn Owl are obvious, however this information also highlights the suitability of road-side grassy verges for foraging. On this occasion  she does does not successfully capture prey, and moves on to forage elsewhere to try and provision the three chicks which are back at the nest site.
Lots more on this, and more to come, on the Irish Raptor Blog HERE