Predation Danger Can Explain Changes in Timing of Migration: The Case of the Barnacle Goose

Rudy M Jonker,Silke Bauer,Frank Van Langevelde,Götz Eichhorn,Sean Rands

doi:10.1371/journal.pone.0011369

Abstract

Understanding stopover decisions of long-distance migratory birds is crucial for conservation and management of these species along their migratory flyway. Recently, an increasing number of Barnacle geese breeding in the Russian Arctic have delayed their departure from their wintering site in the Netherlands by approximately one month and have reduced their staging duration at stopover sites in the Baltic accordingly. Consequently, this extended stay increases agricultural damage in the Netherlands. Using a dynamic state variable approach we explored three hypotheses about the underlying causes of these changes in migratory behavior, possibly related to changes in (i) onset of spring, (ii) potential intake rates and (iii) predation danger at wintering and stopover sites. Our simulations showed that the observed advance in onset of spring contradicts the observed delay of departure, whereas both increased predation danger and decreased intake rates in the Baltic can explain the delay. Decreased intake rates are expected as a result of increased competition for food in the growing Barnacle goose population. However, the effect of predation danger in the model was particularly strong, and we hypothesize that Barnacle geese avoid Baltic stopover sites as a response to the rapidly increasing number of avian predators in the area. Therefore, danger should be considered as an important factor influencing Barnacle goose migratory behavior, and receive more attention in empirical studies.

Highlights

In migratory species, flexibility allows dealing with a continuously changing environment
We considered 4 different locations: a wintering site in the Netherlands, stopover sites in the Baltic sea region and at the Kanin peninsula in Russia, and a breeding site N at the Barents Sea coast in Russia [35]
Advancing the onset of spring in the Baltic by a given unit of time led to an advanced departure date from the wintering site for most of the range tested in our simulations

Summary

Introduction

Flexibility allows dealing with a continuously changing environment. Sutherland [1] presented an overview of bird species that showed flexibility in their migratory behavior to changing environmental conditions. He described changes in the use of wintering, breeding and staging areas, occurring in a wide range of families. Gill et al [4] for example, showed that an increasing population of Black-tailed godwits Limosa limosa islandica, wintering in the UK, established new wintering sites on less suitable sites than the original wintering sites They suggested that the carrying capacity of the original sites was reached, forcing the Black-tailed godwits to winter elsewhere. Identifying possible causes of these changes, is essential for understanding flexibility in migratory behavior

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Conclusion