Unexpected variation in migration routes and nonbreeding residency of Tree Pipits (Anthus trivialis) from a central European breeding population

Abstract The natural history of migration comprises a set of population-specific ecological and flexible traits, that will undergo fundamental changes under current climate alterations, but basic features remain undiscovered for many species and populations. Here, we provide the first spatiotemporal annual cycle information of individual Tree Pipits ( Anthus trivialis ), one of the most common long-distance African-Palearctic migrants. Male pipits from Czechia showed a large variation in migration routes and African nonbreeding residence sites. In autumn, birds crossed the Mediterranean basin over a wide range from its western to eastern part to reach nonbreeding sites in West Africa, Nigeria, and the Lake Chad area. Nonbreeding residence period lasted on average 160 days, wherein 28% of males showed site itinerancy of 100 km and 400 km between overwintering sites. Northbound spring migration routes differed entirely or in the North-African European portion from autumn (post-breeding) routes, resulting in seasonally different passage regions. Departure periods from the breeding sites in autumn and the nonbreeding sites in spring spanned over a 1.5- and 1 month period, respectively. Migration duration per bird in spring lasted 20 days (median) which was 61% shorter than the duration of autumn migration (median: 52 days). Our study shows that Tree Pipits from a single breeding population pass through and reside across vast areas and thus, experience a wide array of environmental conditions outside their breeding season. To establish a causal link between environmental conditions and the population trajectory of Tree Pipits, further tracking information are required especially from northern and eastern European breeding populations.