Crop type influences edge effects on the reproduction of songbirds in sagebrush habitat near agriculture

Abstract

ABSTRACT. Extensive fragmentation of the sagebrush shrubsteppe of western North America could be contributing to observed population declines of songbirds in sagebrush habitat. We examined whether habitat fragmentation impacts the reproduction of songbirds in sagebrush edge habitat near agriculture, and if potential impacts vary depending on the adjacent crop type. Specifically, we evaluated whether nest abundance and nest survival varied between orchard edge habitat, vineyard edge habitat, and interior habitat. We then examined whether the local nest predator community and vegetation could explain the differences detected. We detected fewer nests in edge than interior habitat. Nest abundance per songbird was also lower in edge than interior habitat, although only adjacent to vineyards. Nest predation was more frequent in orchard edge habitat than vineyard edge or interior habitat. Predators identified with nest cameras were primarily snakes, however, reduced nest survival in orchard edge habitat was not explained by differences in the abundance of snakes or any other predator species identified. Information theoretic analysis of daily survival rates showed that greater study plot shrub cover and lower grass height at nests were partially responsible for the lower rate of predation-specific daily nest survival rate (PDSR) observed in orchard edge habitat, but additional factors are likely important. Results of this study suggest that different crop types have different edge effects on songbirds nesting in sagebrush shrubsteppe, and that these reproductive edge effects may contribute to observed declines of these species. Habitat managers should avoid the creation of new orchard-sagebrush habitat edges to avoid further impacts on already declining songbird populations.Effet de bordure sur la reproduction de passereaux dans des milieux d'armoises variable selon le type de culture adjacente RÉSUMÉ. La fragmentation à grande échelle de la steppe arbustive à armoises de l'ouest de l'Amérique du Nord contribue peut-être aux déclins observés des passereaux des milieux d'armoises. Nous avons examiné si la fragmentation avait un impact sur la reproduction des passereaux dans des milieux d'armoises en bordure de milieux agricoles, et si les effets potentiels variaient selon le type de culture adjacente. Plus particulièrement, nous avons évalué si le nombre de nids et leur survie différaient entre les milieux de bordure de vergers, les milieux de bordure de vignobles et les milieux d'intérieur. Nous avons ensuite examiné si la communauté locale de prédateurs de nids et la végétation pouvaient expliquer les différences détectées. Nous avons trouvé moins de nids dans les milieux de bordure que dans les milieux d'intérieur. Le nombre de nids par espèce était également plus faible dans les bordures par rapport aux milieux d'intérieur, mais ce, seulement près des vignobles. La prédation des nids était plus fréquente dans les bordures de vergers que dans les bordures de vignobles ou les milieux d'intérieur. Les prédateurs identi...

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

“…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). These evidences, and our data suggest that camera systems based on motion sensors rarely achieve 100% efficiency in the detection of predators, as occurs, for example, with most devices with full time recording (time-lapse devices) (Sabine et al 2005, Pierce and Pobprasert 2007, Gula et al 2010, Kirkpatrick and Conway 2010, Smith et al 2012, Denmon et al 2013.…”

“…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.…”

“…In this study, although we did not observe snakes depredating nests, we filmed a small specimen of the genus Echinanthera Cope, 1894 passing in front of a nest of Gray-hooded Flycatcher, but the snake was apparently not attracted by the contents. Knight et al (2014) used the same type of camera traps as those in this study and identified snakes as the primary predators of songbird nests in the sagebrush shrub-steppe of North America. These are evidences that our camera traps could detect snakes, particularly within the 1 to 3 m distance that is used in most studies.…”

“…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).…”

The new faces of nest predation in agricultural landscapes—a wildlife camera survey with artificial nests

“…Besides recognizing the impact of predators on prey populations, certain studies have attempted to distinguish the influence of landscape structure, especially the edge effect on nest predation, with varying results (Major and Kendal 1996;Andrén and Angelstam 1988;Lahti 2001;Evans 2004;Ellis-Felege et al 2012;Knight et al 2014). Andrén (1992) showed that Eurasian jays (Garrulus glandarius) and common ravens (Corvus corax) preyed within larger forest fragments and avoided smaller patches, whereas magpies (Pica pica) and Eurasian jackdaws (Corvus monedula) preferred agricultural land for nest predation.…”