Evaluating the potential effects of capturing and handling on subsequent observations of a migratory passerine through individual acoustic monitoring

Abstract

Ringing is the most common technique used for individual marking of passerine birds, informing understanding of many aspects of their behaviour and ecology. Birds caught for ringing may also be substantially handled before release (e.g. to obtain biometric data, blood or feather samples), and all such procedures may affect the subsequent behaviour of a captured individual. Previous field studies that have assessed the potential effects of capturing and handling birds have nevertheless, to date, lacked an entirely independent unhandled control. In this study, we used individual acoustic monitoring to compare the apparent survival and re-encounter probabilities of male tree pipits Anthus trivialis that were captured with mist nets and intensively handled (measured, blood-sampled and ringed) with those of a control group of unhandled birds tracked solely by their vocalization. There were no differences between handled and unhandled birds in apparent survival rates, either in simple annual estimates, or in jointly estimated within-and between-breeding season survival estimates. Re-encounter probabilities in the latter analysis peaked at the start of the breeding season, when song activity would be expected to be greatest, but were higher for handled than unhandled birds in mid-to late May. Apart from demonstrating that tree pipits were not affected in the long-term by capture and associated handling, our study confirms that individual acoustic monitoring is a valuable non-intrusive method for long-term monitoring studies.

Guess who? Evaluating individual acoustic monitoring for males and females of the Tawny Pipit, a migratory passerine bird with a simple song

“…In this way, birds can discriminate between familiar and unfamiliar conspecifics in different social contexts (e.g., neighbour vs. stranger discrimination, parent-offspring recognition, kin recognition; Lambrechts and Dhondt 1995). Not only do vocal signatures play an important role in social interactions, but under some circumstances they can also be effectively used to monitor bird individuals (e.g., Blumstein et al 2011;Petrusková et al 2016Petrusková et al , 2021Sebastián-González et al 2018;Pérez-Granados et al 2019).…”

“…Acoustic monitoring does not require the manipulation of trapped individuals, unlike more traditional mark-recapture methods (e.g., use of mist nets or clap traps for capturing and subsequent ringing). Though these catch-and-ring techniques do not necessarily have a negative effect on bird survival and fitness (e.g., Calvo and Furness 1992;Clewley et al 2018;Petrusková et al 2021), playback luring plus capturing and handling may have cumulative effects on the subsequent behaviour of passerines (Linhart et al 2012;Budka et al 2019;Oñate-Casado et al 2021). In contrast, due to its non-invasive approach IAM can be used on wild species with fewer concerns about impacts on the behaviour of target individuals (reviewed in Terry et al 2005), and might even provide more accurate information about behaviour or population dynamics (e.g., Laiolo et al 2007;Petrusková et al 2016).…”