Stopover strategies in birds: a review of methods for estimating stopover length

This study categorizes and reviews methods used to estimate stopover length in migratory birds. Stopover length is an important variable in analysing migration strategies. The analysis of the stopover pattern of migratory birds typically attempts to investigate variability in the number of stopovers and in the length of time spent at stopover sites in relation to species, age, sex and body condition. Although the number of capture-recapture studies analysing stopover length has increased substantially, most are analysed using the simple last-first capture method which gives biased estimates. The use of mathematical models to calculate stopover length is uncommon. Most researchers assume homogeneity in stopover length and do not determine the capture probability. Intensive studies are available for many migratory passerines, waders and geese. Some of the data sets are highly standardized and could be reanalysed with new applications and innovative uses of existing techniques, such as the CJS models.