Adjustable leg harness for attaching tags to small and medium‐sized birds

Abstract

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.

Light and thermal niches of ground‐foraging Amazonian insectivorous birds

“…The proportion of available light used-a more robust measure of exposure that incorporated concurrent weather-agreed that birds used an exceptionally shaded microclimate: as a guild, terrestrial insectivores used ~4% of midday light in their habitat on the forest floor, with the GRVA and MYCA exposed to ~1% of ambient levels. Although we cannot rule out some level of feather shading, sensors perched ~1 cm above the skin, most species were relatively small (Jirinec et al, 2021b), and the warm conditions birds occupied were unlikely to induce feather ruffling for thermoregulation. Therefore, we interpret these results as active selection of low-light microhabitat.…”

“…The light sensor spectral response corresponded well with the spectral response of avian vision (Ausprey et al, 2021). We fixed tags with a leg‐loop harness (Jirinec et al, 2021b); light readings therefore reflected direct exposure to light striking the bird's dorsal region (between the back and rump), whereas temperature was a mix of air temperature ( T a ) and T b . Loggers were programmed to sample light and temperature every 5 and 15 min, respectively, for final sample sizes of >3 million light and >900,000 temperature readings (Table 1).…”

“…Loggers were programmed to sample light and temperature every 5 and 15 min, respectively, for final sample sizes of >3 million light and >900,000 temperature readings (Table 1). For more details about bird capture, harness, and the lack of harmful tag effects, please refer to Jirinec et al (2021b).…”

“…), and cup (all others) nesters. Individual-specific microclimate use was measured by loggers placed on birds for ~1 year (Jirinec et al, 2021b).…”

Morphological consequences of climate change for resident birds in intact Amazonian rainforest

“…Terrestrial insectivores are seldom captured with passive netting because of their ambulatory locomotion, and this ecological guild has become rare in recent years ( 9 ) and thus of particular interest in this study. For a sufficient sample for terrestrial insectivores, we included birds lured into nets with playback in 2017–2019 ( 59 ), with captures throughout the day. Although some temperate birds may weigh less in the morning ( 60 , 61 ), the inclusion of potentially heavier individuals obtained by target netting (i.e., with some measured late in the afternoon) would work contrary to the predicted lower mass in the latter years.…”