Neckband or backpack? Differences in tag design and their effects on GPS/accelerometer tracking results in large waterbirds

Abstract

Background: GPS and accelerometer tracking presently revolutionises the fields of ecology and animal behaviour. However, the effects of tag characteristics like weight, attachment and data quality on study outcomes and animal welfare are important to consider. In this study, we compare how different tag attachment types influence the behaviour of a group of tagged large waterbirds, GPS accuracy and behaviour classification success from accelerometer data.Results: Both neckband and backpack tags had similar effects on the behaviour of six captive Canada geese (Branta canadensis), increasing the amount of discomfort behaviour in relation to untagged individuals. Both treatment groups also slightly decreased the amount of foraging, but the duration of neither vigilance nor resting was affected. GPS positions that were filtered with classical GPS platform settings (i.e. smoothing) were more accurate than positions improved by satellite-based differential augmentation. Tag attachment, however, did not induce any differences in position accuracy of both data types. Behaviour classification success was generally similar for neckband and backpack tags. But in detail, behaviours mainly performed by the head like foraging and vigilance were better detected from accelerometer data of neckband tags, whereas behaviours like resting and walking were more successfully detected from backpack tag data. Conclusion:Our findings suggest that the use of neckband or backpack tags for tracking large waterbirds and their behaviour largely depends on which behaviours are most important to detect. However, for wildlife tracking studies, factors like tag retention time are also of great importance, especially for animals like some goose species that are known to quickly destroy backpack tags. For future studies, we advise to carefully evaluate not only tag weight, but also attachment methods and data quality, because the right choice depends on the research question. This will improve the scope of wildlife tracking even more for various scientific, conservation and management applications.

Agricultural pastures challenge the attractiveness of natural saltmarsh for a migratory goose

“…In next spring (2013), six and four birds returned with working tags to fuel at the pasture and saltmarsh site, respectively, and no switches between the two habitat types were observed between years, nor within seasons (Fokkema et al., ). Because it may take some weeks for waterfowl to get accustomed to a tag (Kölzsch et al., ; Nuijten et al., ), we used this following spring for quantifying time budgets. Our birds frequently preened in the days after capture, but such behaviour was no longer observed next year.…”

Reduction in adverse effects of tracking devices on waterfowl requires better measuring and reporting

“…In a captivity experiment, Kölzsch et al [44] reported no difference in behaviour between Canada Geese equipped with neck collar transmitters or backpack transmitters, but both groups tended to spend more time preening and less time feeding. Increased preening behaviour was also observed in a study on captive Bewick's Swans C. columbianus bewickii with neck collar transmitters, but this effect had disappeared after 6 weeks [57].…”

“…Neck collars were used more often in the early 2000s, but have been used irregularly in the past 10 years. Apart from differences between attachment methods in adverse effects for waterfowl, the choice of attachment method should also depend on the research question of the researcher [44]. Harness-attached backpacks have the benefit of bringing the tracking device close the centre of gravity of the bird [44], while its placement on the back creates a large surface for charging of solar panels.…”

“…Apart from differences between attachment methods in adverse effects for waterfowl, the choice of attachment method should also depend on the research question of the researcher [44]. Harness-attached backpacks have the benefit of bringing the tracking device close the centre of gravity of the bird [44], while its placement on the back creates a large surface for charging of solar panels. Transmitter implantation in the abdominal cavity is sometimes preferred over the use of backpacks, especially in diving species, since this overcomes the problem of interruption of the waterproof plumage, as well as the problem of drag created by external devices during flying or diving.…”

“…For these species, a neck collar can be more suitable than a backpack, as it diminishes the area over which abrasion and drag occurs, and lacks a harness which can be wrongly adjusted to the bird's shape and disrupts the plumage. However, as the weight of the tag is not positioned at the centre of gravity, this may become problematic for the bird when tags are relatively heavy [44]. In general, we found that neck collars used in studies are lighter (in mass relative to the bird's body mass) than harness-attached or implanted tags (backpack vs. neck collar: t 185, 33 = 8.26, p < 0.001; implant vs neck collar: t 105,33 = 8.34, p < 0.001).…”