Response of vertebrate scavengers to power line and road rights-of-way and its implications for bird fatality estimates

Joana Bernardino,Ricardo C Martins,Regina Bispo,Francisco Moreira,Sara Santos

doi:10.1038/s41598-020-72059-7

Abstract

Linear infrastructures, such as power lines and roads, are an important source of bird mortality. However, little is known on the potential effect of these infrastructures on local scavenger guilds, their foraging activity and the resulting bird carcass removal patterns. This is an important source of bias in studies aiming to quantify bird fatalities due to linear infrastructures. We used camera-traps to record scavenger identity and persistence patterns of bird carcasses placed close to linear infrastructure and nearby controls in two Mediterranean agricultural regions. We found that linear infrastructure influence on scavenger identity varied depending on the region. Contrary to expectations, linear infrastructure presence had either none or a positive effect on carcass persistence, meaning that carcasses placed within power line or road rights-of-way were not removed faster than the ones placed in controls. We conclude that linear infrastructure effect on vertebrate scavenging patterns is likely to be region-specific, and that reliable correction factors for carcass removal-bias in bird fatality estimates require site-specific experiments to characterize local scavenging processes.

Highlights

Linear infrastructures, such as power lines and roads, are an important source of bird mortality
Carcass persistence rates are typically evaluated through field experiments where a known number of bird carcasses is distributed along Linear infrastructures (LI) rights-of-way and regularly monitored until no detectable remains are left
We found that carcasses were detected and removed by scavengers at high rates in both our study regions. This pattern of rapid scavenging has previously been observed in road verges and power lines that bisect agricultural landscapes (e.g.10–12), as well as for other anthropogenic sources of bird mortality, like wind farms, fences and pesticides (e.g.21,25,57)

Summary

Introduction

Linear infrastructures, such as power lines and roads, are an important source of bird mortality. Little is known on the potential effect of these infrastructures on local scavenger guilds, their foraging activity and the resulting bird carcass removal patterns This is an important source of bias in studies aiming to quantify bird fatalities due to linear infrastructures. To avoid the so-called scavenger swamping (i.e., abnormal carcass removal by scavengers, due to a saturation of the study area with c arcasses16), it is recommended that carcasses are placed at least 100–500 m distanced apart (e.g.17,18) This requirement greatly restricts the number of carcasses to be placed simultaneously within the LI right-of-way, technicians have often questioned the possibility of distributing carcasses in nearby areas (with similar habitats) to achieve the optimal sample size. Entirely the conditions of LI rights-of-way, with unknown consequences for the accuracy of the scavenging–bias correction factor derived

Methods

Results

Conclusion