Nest Site Selection by Kentish Plover Suggests a Trade-Off between Nest-Crypsis and Predator Detection Strategies

Miguel Ángel Gómez-Serrano,Pascual López-López

doi:10.1371/journal.pone.0107121

Abstract

Predation is one of the main causes of adult mortality and breeding failure for ground-nesting birds. Micro-habitat structure around nests plays a critical role in minimizing predation risk. Plovers nest in sites with little vegetation cover to maximize the incubating adult visibility, but many studies suggest a trade-off between nest-crypsis and predator detection strategies. However, this trade-off has not been explored in detail because methods used so far do not allow estimating the visibility with regards to critical factors such as slope or plant permeability to vision. Here, we tested the hypothesis that Kentish plovers select exposed sites according to a predator detection strategy, and the hypothesis that more concealed nests survive longer according to a crypsis strategy. To this end, we obtained an accurate estimation of the incubating adult's field of vision through a custom built inverted periscope. Our results showed that plovers selected nest sites with higher visibility than control points randomly selected with regards to humans and dogs, although nests located in sites with higher vegetation cover survived longer. In addition, the flushing distance (i.e., the distance at which incubating adults leave the nest when they detect a potential predator) decreased with vegetation cover. Consequently, the advantages of concealing the nest were limited by the ability to detect predators, thus indirectly supporting the existence of the trade-off between crypsis and predator detection. Finally, human disturbance also constrained nest choice, forcing plovers to move to inland sites that were less suitable because of higher vegetation cover, and modulated flushing behavior, since plovers that were habituated to humans left their nests closer to potential predators. This constraint on the width of suitable breeding habitat is particularly relevant for the conservation of Kentish Plover in sand beaches, especially under the current context of coastal regression and increase of recreational activities.

Highlights

Predation is the main cause of breeding failure for groundnesting birds [1] and one of the most important causes of adult mortality, during incubation [2]
38 nests were located in tidal debris, 56 in embryonic shifting dunes, 80 in shifting dunes and 142 in semi-fixed dunes
Nests on tidal debris and embryonic shifting dunes had higher failure rates (26.32% and 30.36% respectively) than those that were located in shifting dunes and semi-fixed dunes (16.25% and 20.42%, respectively)

Summary

Introduction

Predation is the main cause of breeding failure for groundnesting birds [1] and one of the most important causes of adult mortality, during incubation [2]. Birds vulnerable to predation during reproduction, such as groundnesting species, tend to produce abundant offspring and employ strategies to minimize the risk of adult and egg predation [4,5,6]. Predation risk on adults and eggs can be minimized through an adequate nest choice, in ground-nesting species. Other studies suggest a trade-off between nest crypsis and the ability of incubating adults to detect predators [7,16,17,18]

Methods

Results

Conclusion