Adjustable Leg Harness For Attaching Tags To Small And Medium-Sized Birds

Rapidly expanding use of biologging devices is increasingly bringing novel insights into ornithology. Consequently, to maximize bird welfare and data quality, this growth calls for ensuring that devices are properly attached. Here, we provide a diagram for constructing a simple, field-adjustable leg-loop harness suitable for many small and medium-sized birds (< 200 g). We make harnesses prior to fieldwork using Teflon ribbon and a single crimp, then custom-fit each harness to birds in the field. This largely removes the need for pre-deployment field trials to determine harness size and ensures best possible fit. To evaluate the effects of harnesses on birds in the field, we marked 10 non-migratory species in central Amazonia and assessed their body mass at recapture with linear mixed models. Of 90 tags deployed, we recovered 43 (48%) an average of 359 days later. No individuals lost their tag. Additionally, when recaptures were compared to original captures, body mass was not lower for either tagged birds or 17 banded-only birds. This suggests that tags attached with our harness had little effect on birds, an encouraging result at a time when increasing options for tracking birds challenge researchers to properly attach various types of devices.