Monitoring passerine reproduction by constant effort ringing: evaluation of the efficiency of trend detection

avian populations is more than a century old (Greenwood 2009). In the first decades of bird ringing, the method was applied almost exclusively to answer questions about avian migration; how far do birds fly and which routes do they take? Beginning in the late 1960s, ornithologists began to monitor breeding population sizes using standardised mist netting (Robinson et al. 2009). Later the focus shifted to the study of processes underlying population change, namely the determination of demographic parameters such as birth and death rates, leading to the foundation of the first nation-wide constant effort scheme in Great Britain and Ireland in 1986 (Peach et al. 1996). The Dutch constant effort site (CES) programme followed in 1994 and since then has been continuously operated by hundreds of enthusiastic citizen scientists under the direction of the Vogeltrekstation – Dutch Centre for Avian Migration Monitoring passerine reproduction by constant effort ringing: evaluation of the efficiency of trend detection