Reproductive Performance of a Declining Forest Passerine in Relation to Environmental and Social Factors: Implications for Species Conservation

Abstract

Identifying factors influencing a species' ecological niche and demography is a prerequisite for species conservation. However, our understanding of the interplay between demographic rates and biotic/abiotic factors is still poor for most species of conservation concern. We evaluated relevance of eight hypotheses relating to timing of breeding, temporal nest exposure, nest concealment, topography, tree structure, predation risk and disturbance, density dependence and weather for explaining variation in reproductive performance of the declining wood warbler Phylloscopus sibilatrix in northern Switzerland. Reproductive performance was monitored with cameras at 136 nests from 2010 to 2012 and was associated to temporal exposure, timing of breeding and concealment of nests. Daily nest survival was positively related to the number of grass and sedge tussocks, nest concealment and nest age. Clutch size and number of fledglings decreased, the later in the season a nest was initiated. Nest survival over an average nesting period of 31 days was 46.9 ± 0.07% (mean ± SE), daily nest survival rate was 0.976 ± 0.002. As for many ground-breeding birds, nest predation was the principal cause of nest failure, accounting for 79% of all nest losses. Conservation measures should aim at increasing the area of relatively homogenous forest stands featuring suitable habitats characterized by abundant and accessible grass and sedge tussocks. In managed forests, such conditions can be found in stands of middle age (i.e. pole wood) with little to no shrub layer.

Testing camera traps as a potential tool for detecting nest predation of birds in a tropical rainforest environment

“…A number of studies have used camera traps to monitor nest predation, and they frequently detect most of the predation events. For small passerines, Grendelmeier et al (2015) successfully identified predators in 84% of 57 depredated nests of the Wood Warbler Phylloscopus sibilatrix (Bechstein, 1793) in northern Switzerland. Knight et al (2014) (Pallas, 1764).…”

“…Although the statistical significance of predator detection was not affected, we also recommend the use of two cameras per nest, because the predators were identified by only one of the cameras in many nests. In previous studies that used camera traps for a similar purpose, all were conducted in temperate habitats (Knight et al 2014, Thiebot et al 2014, Davies et al 2015, Grendelmeier et al 2015, but, based on the results of this study, camera traps are also appropriate to monitor nest predation in tropical rainforest environments.…”

“…The camera traps also print relevant data on photographs and videos, such as time, date, and temperature (O'Brien and Kinnaird 2008). Camera traps have been successfully used, for example, to estimate the abundance of marked birds (O'Brien and Kinnaird 2008), to study habitat use (O'Brien and Kinnaird 2008, Srbek-Araujo et al 2012, Kuhnen et al 2013, diet (Renner et al 2012, García-Salgado et al 2015, social organization (Srbek-Araujo et al 2012), daily and seasonal activity patterns (Srbek-Araujo et al 2012, Kuhnen et al 2013, Dias et al 2016, nesting behavior (Rollack et al 2013), and in a few recent studies, they were used to identify nest predators (Knight et al 2014, Thiebot et al 2014, Davies et al 2015, Grendelmeier et al 2015. In studies that identified nest predators, the delay in triggering and the inability to detect small predators were the primary potential drawbacks impeding broader use of camera traps (O'Brien and Kinnaird 2008).…”

Does acoustically simulated predation risk affect settlement and reproduction of a migratory passerine?

“…Using camera traps, these species have been identified as main predators of wood warbler nests in Western Europe (Grendelmeier et al, 2015;Mallord et al, 2012;Maziarz, Piggott, et al, 2018). Using camera traps, these species have been identified as main predators of wood warbler nests in Western Europe (Grendelmeier et al, 2015;Mallord et al, 2012;Maziarz, Piggott, et al, 2018).…”

“…Based on these findings, it can be hypothesized that wood warblers actively avoid breeding sites with high rodent densities. ), red fox (Vulpes vulpes) and tawny owl (Strix aluco) throughout the species' range, and non-rodent-hunting Eurasian jay (Garrulus glandarius, hereafter jay) in Western Europe are the most important predators of wood warbler nests (Bellamy et al, 2018;Grendelmeier et al, 2015;Mallord et al, 2012;Maziarz, Grendelmeier, et al, 2018;Maziarz, Piggott, et al, 2018), and nest survival is lower in years with high rodent abundance compared to other years . One such factor may be the presence of rodent-hunting predators, for which numerical increases in response to high rodent numbers have been shown (e.g., Jȩdrzejewski, Jȩdrzejewska, & Szymura, 1995;Schmidt & Ostfeld, 2003).…”