Acute impacts from Teflon harnesses used to fit bio-logging devices to Black-legged Kittiwake Rissa tridactyla

Biologging devices including GPS and satellite tags, which attach to individual animals and collect information on their movements, are increasingly deployed in ecology and conservation research. They can be particularly useful for species like seabirds, which are otherwise hard to monitor as they spend so much of their lives in inaccessible environments. Many seabird species spend most of their lives far out in the open ocean, where visual surveillance, particularly of focal individuals, is almost impossible. Even when they come to land, during the breeding season, their breeding sites may be on dangerous cliff ledges or deep, fragile burrows. At the same time, large numbers of seabird species are in decline, so it is essential to better understand their life cycles to identify pinch points and effectively target conservation action.

BTO scientists have been attaching GPS devices to seabirds for more than a decade. While this has proved successful for some species, including Herring Gulls and Lesser Black-backed Gulls, it has been problematic for others. For example, Great Skuas failed to return to their nest sites the year after they were GPS-tagged, leading BTO to cancel this particular strand of research.

In this study, BTO scientists collaborated with others to assess the impact of attaching tagging devices to Kittiwakes breeding in the UK and Norway. The Kittiwake is on the UK Birds of Conservation Concern Red List, having undergone a sharp reduction in numbers in recent decades. It is a small, surface feeding gull that has a more maritime lifestyle than other gull species successfully tagged by BTO. The researchers trialled different harness types for attaching tags – one that looped around the birds’ legs, and another that fitted around the birds’ wings and thorax – and then recaptured the birds 10-24 days later to examine whether there had been any adverse effects. They also monitored the birds at their breeding colony, and compared their behaviour to that of control birds, which were captured and ringed, but were not fitted with a tracking device.

The study showed damage to the tagged Kittiwakes’ feathers and skin around the area under the tag and the tag’s harness. This damage, which included feather wear and skin lesions, was worse for the thoracic harness than for the leg-loop version – the birds fitted with leg-loop harnesses showed abrasion to the feathers but not the skin. Kittiwakes are known to lose weight during the breeding season, but this effect was marginally worse in tagged birds than in the control cohort. 

As a result of this study, the authors recommend that thoracic harnesses should not be used on Kittiwakes. Leg-loop harnesses could still be a viable option, especially if different harness materials are trialled, for example those that are more elastic than the Teflon cord used in this study. This work underlines the importance of continually assessing the suitability of tracking technology for different species, and reporting unsuccessful results to both ensure negative impacts are not repeated between multiple studies but also to improve overall practice. Small differences in the materials, design or procedure can be very important in tracking studies and through continual appraisal, some species can now be safely tracked which could not have been previously.

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