Seasonal increase of nest height of the Silver-throated Tit (Aegithalos glaucogularis): can it reduce predation risk?

Haohui Guan,Pengcheng Wang,Jiliang Xu,Jianqiang Li,Ye Wen,Lei Lv

doi:10.1186/s40657-018-0135-4

Haohui Guan, Pengcheng Wang + Show 4 more

Open Access

https://doi.org/10.1186/s40657-018-0135-4

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Abstract

BackgroundNest predation is usually the main cause of bird nest failure. ‘Predation avoidance hypothesis’ of nest-site selection predicts that birds should prefer nest-sites with higher nesting success. We investigated the relationship between nest height and nest fate in Silver-throated Tits (Aegithalos glaucogularis) and asked whether the seasonal change of nest height was adaptive by simultaneously analyzing the seasonal variation of predation rates of the nests.MethodsWe monitored nests of the Silver-throated Tit across seven breeding seasons in the Dongzhai National Nature Reserve in Henan Province of China. We compared the difference of nesting success among nests of different heights and analyzed the effect of nesting date on nest height and nest predation rates.ResultsThe overall nesting success rate was 24.1% (n = 623). Among the failed nests (n = 472), 59.75% were predated by birds and mammals, followed by snakes (9.11%). The average height of successful nests was significantly lower than that of predated nests. As the season progresses, the height of the nests increased significantly, companied by the decrease in nesting success. Daily survival rate of the nests also decreased with the progression of the season, regardless of breeding stages.ConclusionsOur findings suggest that nest height is an important factor influencing the nesting success of Silver-throated Tits. However, the seasonal increase of nest height appears inconsistent to the ‘predation avoidance hypothesis’, because it is associated with higher predation rates. The reason for this maladaptive behavior remains to be explored in future studies.

Highlights

Nest predation is usually the main cause of bird nest failure
This ‘predation avoidance hypothesis’ of nest-site selection predicts that birds should adjust their nest-site preference according to varied predation risks
We investigated the relationship between nest site and nest fate in Silver-throated Tits (Aegithalos glaucogularis) and asked whether the seasonal change of nest height was adaptive by simultaneously analyzing the seasonal variation of predation rates of the nests

Summary

Introduction

Nest predation is usually the main cause of bird nest failure. ‘Predation avoidance hypothesis’ of nestsite selection predicts that birds should prefer nest-sites with higher nesting success. The increase of coverage and complexity of vegetation surrounding the nest can reduce nest predation rates (Holway 1991; Martin 1993; Arriero et al 2006; Hollander et al 2015; Buehler et al 2017; Bellamy et al 2018), and birds are expected to place their nests with good concealment (Lima 2009). This ‘predation avoidance hypothesis’ of nest-site selection predicts that birds should adjust their nest-site preference according to varied predation risks. In accordance with this hypothesis, parent birds were found to prefer safer nest sites when predation risk was high in both Dusk Warbler (Phylloscopus fuscatus) (Forstmeier and Weiss 2004) and Siberian Jay (Perisoreus infaustus) (Eggers et al 2006)

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