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

Table 1 Numbers and fractions (between brackets) of studies reporting effects of different types of tracking devices

	Backpack harness	Implant	Subcutaneous	Neck collar	Other	Total
Reported	45/112 (0.40)	25/59 (0.42)	6/14 (0.43)	9/23 (0.39)	3/6 (0.50)	84/202 (0.42)
Control group	8/45 (0.18)	5/25 (0.2)	1/6 (0.17)	4/9 (0.44)	0/3 (0.0)	18/84 (0.21)
Negative	22/45 (0.49)	9/25 (0.36)	1/6 (0.17)	6/9 (0.67)	1/3 (0.33)	39/84 (0.46)
Minor negative	4/22 (0.18)	1/9 (0.11)	0/1 (0.00)	0/6 (0.00)	0/1 (0.00)	5/39 (0.13)
Major negative	18/22 (0.82)	8/9 (0.91)	1/1 (1.00)	6/6 (1.00)	1/1 (1.00)	34/39 (0.87)
Survival	7/18 (0.39)	5/8 (0.63)	1/1 (1.00)	2/6 (0.33)	1/1 (1.00)	16/34 (0.47)
Migration	4/18 (0.22)	2/8 (0.25)	0/1 (0.00)	0/6 (0.00)	0 (0.00)	6/34 (0.18)
Reproduction	8/18 (0.44)	3/8 (0.38)	0/1 (0.00)	6/6 (1.00)	1/1 (1.00)	18/34 (0.53)

The “reported” category includes all studies reporting whether or not an effect was found. The “control group” category includes studies (as a fraction of the studies that report) that contrasted the potential negative effects of tagged birds with a control group. Studies reporting adverse effects (“negative”) were split into studies which found only minor, short-term negative effects (only in the first weeks and not affecting survival, reproduction or migration) and studies which (also) found major, often long-term negative effects. The studies which found long-term negative effects were subdivided into studies reporting effects on survival, migration and reproduction if this information was provided. As in some studies negative effects were found in multiple of the above categories or were not specified, the total number of papers in these categories does not equal the number of studies that found negative effects. No studies reported positive effects of tracking devices

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