Great flexibility in autumn movement patterns of European gadwalls Anas strepera

Abstract

The annual migration cycle of waterbirds often involves several distinct movement stages, for example within‐winter movements or the moult migration during summer, which require a high degree of individual flexibility in migration direction. Here, we investigate whether such flexibility is a common characteristic of waterbird migration by analysing movement behaviour of a dabbling duck, the gadwall Anas strepera, during the little studied, intermediate autumn period. The tracking of individuals via satellite transmitters (n = 7) as well as the ring re‐encounter analysis of three European gadwall populations (Germany, England, Russia) revealed that autumn movements were multidirectional. Furthermore, the comparison with winter re‐encounters suggested that autumn movements were partly independent of the movements towards subsequently used south to southwestern wintering areas. Some individuals even travelled long distances north‐ or eastwards. Accordingly, some autumn locations were characterized by a harsh climate, thus serving as temporary staging sites but necessitating further movements when wetlands freeze during winter. The occurrence of such detours or reversals of migration was confirmed by the transmitter data. Inter‐individual variability in distance and direction of autumn movements was found for both sexes and age‐classes indicating that gadwalls, in general, followed flexible movement strategies. Based on the extent of multidirectional autumn movements, we hypothesize important benefits of such flights and suggest that the analysis of year‐round movement patterns of individual animals during their distinct life‐history stages is essential to understand how they can successfully reproduce and survive.

Dichotomous strategies? The migration of Whimbrels breeding in the eastern Canadian sub-Arctic

“…), others displaying none at all (Gehrold et al. ), and some, especially shorebirds, showing extreme levels of connectivity that limit a population to only a few sites throughout the non‐breeding season (Conklin et al. , Senner et al.…”

Global aerial flyways allow efficient travelling

“…) or safe moulting sites (Gehrold et al . ). An alternative explanation for such spatial detours is that the birds can reduce their energy expenditure due to atmospheric assistance.…”

“…Other pathways are thought to connect patches of suitable habitat along the journey, these so called stopovers sites allow small birds in particular to balance migration and maintaining the energy reserves needed to migrate. Longer than minimal travel routes may thus provide essential resources required for successful completion of the journey such as feeding opportunities or safe moulting sites (Gehrold et al 2014). An alternative explanation for such spatial detours is that the birds can reduce their energy expenditure due to atmospheric assistance.…”

Movement ecology of five Afrotropical waterfowl species from Malawi, Mali and Nigeria

“…For example, the mean direction for Garganey during the spring migration period (206°) seemed inconsistent for an intercontinental north-south migration, but its wide range of movement directions was similar to the finding of directional flexibility in movement patterns of European gadwalls Anas strepera (Gehrold et al 2014). Directionality of long-distance movements for Garganey was likely obscured by numerous within-wetland movements.…”