Comparison of nest defence behaviour between two associate passerines

Marcin Polak

doi:10.1007/s10164-012-0340-2

Abstract

Nest predation is one of the most important factors limiting reproductive success, and antipredator behaviour can significantly reduce the loss of avian broods. I carried out field experiments on two sympatric passerines: the barred warbler and the red-backed shrike. Many authors have described the protective nature of nesting association between these species. However, we have little knowledge about the true nature of the relationships between associates. I examined (1) whether barred warblers and red-backed shrikes respond differently to an avian predator, and (2) whether males and females differ in the intensity of nest defence. Decoys of a known nest predator and a non-predatory control species were used to examine the types and relative intensity of parental response. I measured behavioural responsiveness by recording aggressive behaviour toward each model during the nestling period. Barred warblers and red-backed shrikes showed considerable variation in their response. Warblers more vigorously defended their own territories than shrikes. No differences between the sexes in antipredator behaviour in red-backed shrike were found. By contrast, in barred warbler, male was more involved in nest defence. The experimental tests provide evidence that these two species are able to differentiate between a predator and non-predator species.

Highlights

Recent empirical studies have suggested that positive interactions may be common, predictable and pervasive important forces in different ecosystems (Blanco and Tella 1997; Martin and Martin 2001; Quinn et al 2003; Sergio et al 2004; van Kleef et al 2007; Nocera et al 2009)
One such strategy is the creation of protective nesting associations in which one or more species relate and directly benefit from nesting within the protective umbrella created by other species (Blomqvist and Elander 1988; Halme et al 2004)
In birds reproductive success may increase with the number of close, aggressive neighbours, including heterospecifics and conspecifics, because recent studies suggest a direct relationship between group size and mobbing intensity (Pavel and Bures 2001; Grim 2008; Krama et al 2012)

Summary

Introduction

Recent empirical studies have suggested that positive interactions may be common, predictable and pervasive important forces in different ecosystems (Blanco and Tella 1997; Martin and Martin 2001; Quinn et al 2003; Sergio et al 2004; van Kleef et al 2007; Nocera et al 2009). Protection of broods from predators using aggressive behaviour of other species is one of the most unusual strategies used by birds to evade predation (Clark and Robertson 1979; Norrdahl et al 1995). One such strategy is the creation of protective nesting associations in which one or more species relate and directly benefit from nesting within the protective umbrella created by other species (Blomqvist and Elander 1988; Halme et al 2004).

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Conclusion