Tags temporarily decrease takeoff velocity and trajectory in Passer domesticus (House Sparrow)

We examined how mock tracking devices 5.7% of body mass impact takeoff flight velocity, wingbeat frequency, trajectory, and change in body mass using 84 Passer domesticus (House Sparrow) and two tag attachment styles (glue and leg harness). We applied tags and kept them on for a 10-day period with flight trials on day 0 (untagged, then tagged), day 5 (tagged), and day 10 (tagged, then untagged). In the first tagged flight trial birds had lower velocities, but birds’ velocities returned to pre-tagging levels by day 5 for birds with harness tags and by day 10 for birds with glued tags. Day 10 untagged flight trial velocities were higher than day 0 untagged takeoffs. Wingbeat frequency increased in the first tagged flight on day 0 and remained high. Takeoff trajectory was lower in the first tagged flight trial than all other trials. Tags reduced birds’ mass-specific power, which birds partially compensated for by increasing wingbeat frequency, likely increasing energetic costs of flight. Birds tended to lose mass throughout the study, especially those that were heavier for their wing size at the start of the study. Overall, takeoff flight performance was negatively but temporarily impacted by tagging, and more negative impacts were observed when tags were attached via glue rather than with a harness.