Bernardino, J., Bispo, R., Martins, R., Santos, S. y Moreira, F. Effects of linear infrastructures on the composition of local vertebrate scavenger guilds and bird carcass removal patterns in two Mediterranean agricultural landscapes. 2020 IENE International Conference. Abstract book. Évora: Infrastructure & Ecology Network Europe. 2021, Vol. 5.1.2, Num. 5, pags. 128-129. ISSN 978-972-778-182-9
Vertebrate scavengers provide an essential ecosystem service through the removal of carrion in natural landscapes, including wildlife casualties caused by linear infrastructures LI). It is known that local scavenger guilds and their foraging behaviour are greatly influenced by landscape features and carrion availability (among other environmental factors). Thus, there is a growing perception that opportunistic scavengers take advantage of the presence of the LI and increase their predation rates within power line or road rights-of-way (compared to the surroundings), leading to increased bias in the studies aiming to quantify the impacts of these infrastructures on wildlife. Few studies have, however, truly assessed how different types of LI shape the local scavenger community and its cascading effects on carcass persistence. In this study, we used camera traps to assess the effect of the presence of power lines and roads on the identity of the vertebrate scavengers responsible for removing bird carcasses in two Mediterranean agricultural landscapes (both located in central Portugal but with different management regimes) and its effects on overall carcass persistence. During the winter seasons of 2017 and 2018, we monitored for 21 days the scavenging of 250 carcasses of free-ranged quails (Coturnix coturnix) placed along the rights-of-way of two transmission lines (≥150 kV)and a two-lane paved road (each comprising ca. 8 km in length), as well as on two control areas (one in each agricultural landscape).Survival analyses were conducted to assess the effect of type of agricultural landscape, treatment (Power line, Road and Control) and Scavenger group (Raptors, Corvids, Carnivores and Cats/Dogs) on time elapsed until the first scavenging event and time until complete carcass removal. Our results show that avian scavengers tend to find the carcasses before mammals (~1.2 days and~2.6 days, respectively). Nonetheless, most of the scavenging in both agricultural landscapes was carried out by carnivores, with Red foxes (Vulpes vulpes) being responsible for more than45% of the scavenging events. The effect of LI presence on scavengers’ identity and carcass removal rates was not consistent across agricultural landscapes, suggesting that broad generalizations about LI effect on scavenging patterns may not be appropriate. Contradicting common assumptions, LI presence had either no effect or a positive effect on carcass persistence. Carcasses placed next to roads were not removed faster than the ones placed below power lines or at control sites. This result suggests that bias in small- to medium-sized bird mortality estimates resulting from scavengers’ activity at roads may be negligible, particularly when compared with carcass removal resulting from traffic.
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