Citation
Overview
This study assessed the use of glue-mounted GPS tags to track Goosanders in two Scottish river catchments with contrasting management regimes – the Tweed, where licensed shooting occurs, and the Forth, where it does not.
In more detail
Of the 20 tagged birds, 17 yielded usable data, with epoxy adhesive significantly improving tag retention over cyanoacrylate glue. Tracking revealed that Goosanders in the Forth ranged over significantly longer river stretches than those in the Tweed, and all birds showed greater movement during daylight hours. No significant differences were found between sexes. The findings demonstrate the potential of GPS tracking to inform understanding of Goosander ecology and their interactions with fish populations, though improvements in attachment methods are needed for longer-term studies.
Abstract
Capsule
The Goosander, a piscivorous species of duck, can be tracked using GPS tags, with initial results showing that ranging behaviour in spring differed between two river catchments in central and southern Scotland.
Aims
To assess the suitability of a glue-mounted attachment method for GPS tags on Goosanders, and to generate spatial data on Goosander movements.
Methods
20 Goosanders were tagged under licence in two Scottish river catchments and fitted with glue-mounted GPS tracking devices. The data from the tracking devices were analysed using a Brownian bridge movement model approach to generate home range isopleths, which were used to identify linear river sections used by each individual.
Results
Of 20 birds tagged, 17 generated usable data. Tag retention varied from less than 24 hours to 29 days. The lengths of river used differed between the two catchments (per bird at the 95% isopleth level: mean 59.4 km, 95% CI 50.8–68.0 km for one catchment, and mean 18.6 km, 95% CI 11.4–25.9 km for the other catchment) with birds in both catchments making more extensive use of available river habitats during daylight hours.
Conclusions
This study shows the potential for GPS tracking technology to be used to understand the movements of a piscivorous bird species. Tag retention remains a key limitation when tracking Goosanders, due to active removal by the birds, and improvements to attachment methodology are required. This would enable tracking over a greater portion of the Goosander’s annual cycle and would further improve our understanding of the factors determining river use and feeding behaviour of piscivorous birds.
Staff author(s)
Funding was provided by the European Union (European Maritime and Fisheries Fund (SC02457)), the Scottish Government and the Sound Approach.