Individual acoustic monitoring and colour‐ringing yield comparable estimates of male annual survival in a migratory songbird, but differ in breeding season detectability

Monitoring demography is key to understanding how species respond to environmental change; however, in estimating demographic rates it is important to consider any potential biases, for example through the handling and marking of individuals. Individual acoustic monitoring (IAM) provides a non‐invasive method for identifying and tracking individuals, and thus monitoring populations, for species that show reliable individual variation in acoustic signatures that are also stable over time. Here, we aimed to evaluate the relative value of IAM and colour‐ringing and resighting for: (i) monitoring individual male Tree Pipits Anthus trivialis through the breeding season, and (ii) estimating their apparent annual survival. The presence of individual territorial male Tree Pipits was monitored on independent study plots using the two methods through the 2016–2021 breeding seasons in Thetford Forest, eastern England. A robust design survival analysis indicated that colour‐ringing and resighting provided higher re‐encounter probabilities across the breeding season, with those from IAM showing a strong seasonal decline, probably reflecting a decrease in song activity. Consequently, IAM may be less suited for monitoring individuals fully across the breeding season, for example, to follow their breeding attempts or local movements. The two methods provided estimates of apparent annual survival which varied similarly between years, highlighting the value of IAM as an alternative to traditional capture–mark–recapture studies in monitoring male survival. Few studies have used IAM to estimate survival rates to date; the relative merits of the two methods for demographic and breeding season monitoring are discussed.