Fecal sacs do not increase nest predation in a ground nester

Enrique Rubio,B Irene Tieleman,Olivia Sanllorente,Juan Diego Ibáñez-Álamo

doi:10.1007/s10336-018-1566-8

Abstract

Most altricial birds remove their nestlings’ feces from the nest, but the evolutionary forces driving this behavior are poorly understood. A possible adaptive explanation for this could be that birds avoid the attraction of nest predators to their nests due to the visual or olfactory cues produced by feces (nest predation hypothesis). This hypothesis has received contrasting support indicating that additional experimental studies are needed, particularly with respect to the visual component of fecal sacs. To test this hypothesis, we conducted an experiment manipulating the presence of fecal sacs on inactive Woodlark (Lullula arborea) nests. This ground nester has highly cryptic nests that are mainly depredated by visually oriented nest predators (i.e., corvids) in our study population, making it an excellent system to test for the nest predation hypothesis. Our results showed that the presence of fecal sacs in the nest does not seem to be an important factor explaining nest predation. Interestingly, the effect of nest concealment, the most important factor explaining nest predation in Woodlark nests, depended on whether the nest was depredated the previous year or not, supporting the importance of using different nesting sites between years. Our findings indicate that this important nest sanitation behavior is not likely motivated by nest predation and highlight the need to explore alternative selective pressures in this context.

Highlights

Nest sanitation is an important component of parental care, widely present in birds but still poorly understood (IbáñezÁlamo et al 2017)
One of the main hypotheses proposed to explain the removal of nestling feces from the nests of altricial birds is the nest predation hypothesis, which states that the presence of feces in the nest will attract predators (Herrick 1900; Weatherhead 1984; Petit and Petit 1987)
Our results indicate that the best model explaining the effect of the presence of fecal sacs is that containing the interaction of previous-year status by visibility index (Table 1)

Summary

Introduction

Nest sanitation is an important component of parental care, widely present in birds but still poorly understood (IbáñezÁlamo et al 2017). Nest predation is a key factor modulating parental care behaviors in birds such as incubation or food delivery to nestlings (e.g., Ghalambor et al 2013; Morosinotto et al 2013; Hua et al 2014; reviewed in Martin and Briskie 2009; Ibáñez-Álamo et al 2015) According to this hypothesis, the presence of feces in active nests could attract nest predators due to visual or olfactory cues (Ibáñez-Álamo et al 2014a). The authors suggested that their results were difficult to interpret because of the artificial nature of their experiment, which involved using non-specific artificial ground nests and chicken feces covered with a mixture of water and flour Another experimental study using real nestling feces and active Common Blackbird (Turdus merula) nests, found no support for the attraction of nest predators due to feces (Ibáñez-Álamo et al 2014b). Additional studies considering the visual component of nestling feces are required to test whether fecal sacs really attract nest predators

Methods

Results

Conclusion