Abstract
Nomadism is a behaviour where individuals respond to environmental variability with movements that seem unpredictable in timing and direction. In contrast to migration, the mechanisms underlying nomadic movements remain largely unknown. Here, we focus on a form of apparent nomadism in a polygynous shorebird, the pectoral sandpiper (Calidris melanotos). Local mating opportunities are unpredictable and most males sampled multiple sites across a considerable part of their breeding range. We test the hypothesis that individuals decided which part of the breeding range to sample in a given season based on the prevailing wind conditions. Using movement data from 80 males in combination with wind data from a global reanalysis model, we show that male pectoral sandpipers flew with wind support more often than expected by chance. Stronger wind support led to increased ground speed and was associated with a longer flight range. Long detours (loop-like flights) can be explained by individuals flying initially with the wind. Individuals did not fly westwards into the Russian Arctic without wind support, but occasionally flew eastwards into the North American Arctic against strong headwinds. Wind support might be less important for individuals flying eastwards, because their autumn migration journey will be shorter. Our study suggests that individuals of a species with low site fidelity choose their breeding site opportunistically based on the prevailing wind conditions.
Highlights
Flying or swimming animals move within a medium which is in motion itself
The aim of our study is to investigate (i) whether individual pectoral sandpipers use the local wind conditions to decide in which part of the breeding range they will sample potential breeding sites and (ii) how the wind conditions en route influence their flights
We focused on nomadic movements by a polygynous shorebird during the breeding season [27]
Summary
Flying or swimming animals move within a medium which is in motion itself. This means that the animal’s trajectory is the result of their own speed and heading, and the speed and direction of the flow of the medium [1]. For individuals flying towards a specific goal, the use of optimal wind conditions might be constrained or overridden by other factors. Individuals might face trade-offs between waiting for favourable winds and optimal timing [2,21,22], or selection might favour individuals that avoid ecological barriers or cross them on the shortest route, independently of the wind conditions. These factors may define whether individuals benefit from being flexible or consistent with respect to timing and route These factors may define whether individuals benefit from being flexible or consistent with respect to timing and route (e.g. [18]), and determine whether consistency or plasticity in movements are favoured by selection
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