Data and code from: Variable evidence of radio-tag backpacks affecting hummingbird time budgets in captivity

Background: With wildlife-tracking devices miniaturizing rapidly to enable
ever-more research on ever-smaller taxa, there is a newfound urgency for
affordable, field-accessible biologging ethics studies. We designed a
3-hour time-budget experiment to investigate how radio-transmitter
backpacks affect hummingbirds’ behavior in Colombia. Methods: Using a
large flight arena, we individually filmed 25 Black-throated Mangoes
(Anthracothorax nigricollis) under two randomized treatments, tagged and
untagged, to characterize and quantitatively compare behavior. We created
time-budget breakdowns of our behaviors of interest—flying, hover-feeding,
preening, and perching—then fit a series of linear mixed-effects models to
determine the effects of tagging and additional experimental and
environmental variables on behavior. We also designed an aviary-style
“Entanglement Experiment” (n = 30) to determine if any individuals would
snag on vegetation while equipped with the backpack harness, and tested 6
additional birds in this enclosure overnight for any longer-term negative
effects. Results: When tagged, individuals on average spent overall less
time flying (with fewer and shorter bouts); and more total time feeding,
preening (with more and longer bouts in both cases), and perching (with
fewer but longer bouts)—however, this difference in total duration was
only statistically significant in the case of preening. Our best-supported
models also highlighted the importance of the following additional
effects: whether or not the bird was undergoing its first or second
1.5-hour treatment (birds flew significantly more in their second
treatment), bird mass (lighter birds fed significantly longer overall),
and the time of day (birds preened significantly more in the afternoon
than the morning, and more in the evening than the afternoon). No
individuals in this captive study became entangled in vegetation or
exhibited any adverse overnight effects from harness wear. 
Conclusions: In our captive study, radio-transmitter backpacks
significantly affected the amount of time that hummingbirds spent
preening, and additional environmental variables helped explain behavioral
differences in each bird’s treatments. While being in a confined space
doubtlessly affected the behavior of individuals, our experimental model
is relatively straightforward to fine-tune to other small avian taxa and
is suitable for remote conditions, providing a useful basis for examining
species-specific effects of biologging prior to starting field studies.