Assessing Bird Exclusion Effects in a Wetland Crossed by a Railway (Sado Estuary, Portugal)

Abstract

Linear transportation infrastructures may displace wildlife from nearby areas that otherwise would provide adequate habitat conditions. This exclusion effect has been documented in roads, but much less is known about railways. Here we evaluated the potential exclusion effect on birds of a railway crossing a wetland of international importance (Sado Estuary, Portugal). We selected 22 sectors representative of locally available wetland habitats (salt pans, rice paddy fields, and intertidal mudflats); of each, half were located either close to (0-500 m) or far from (500-1500 m) the railway line. Water birds were counted in each sector between December 2012 and October 2015, during two months per season (spring, summer, winter, and autumn) and year, at both low and high tide. We recorded 46 species, of which the most abundant (>70% of individuals) were black-headed gull, greater flamingo, northern shoveler, black-tailed godwit, and lesser black-backed gull. Peak abundances were found in autumn and winter. There was no significant variation between sectors close to and far from the railway in species richness, total abundance, and abundance of the most common species. Some species tended to be most abundant either close to or far from the railway albeit not significantly so but this often varied across the tidal and annual cycles. Overall, our study did not find noticeable exclusion effects of this railway on wetland birds, with spatial variation in abundances probably reflecting habitat selection and daily movement patterns. Information is needed on other study systems to assess the generality of our findings.

The effect of railways on bird diversity in farmland

“…To date, several studies investigated the effect of railways on bird abundance and richness. There were no differences in wetland bird richness and abundances between study plots adjacent to and far from railways (Godinho et al 2017b). Similar to our findings, Li et al (2010) and Wiącek et al (2015) revealed a higher number of birds in railway proximity compared with control points located far from railways.…”

Environmental characteristics of shallow bottoms used by Greater Flamingo Phoenicopterus roseus in a northern Adriatic lagoon

“…Disturbance to waterbirds caused by roads and other man-made structures have been studied elsewhere (Burton et al 2002, Godinho et al 2017, but there appears to be nothing specific to Greater Flamingo, apart from a paper by Yosef (2000), who showed that birds were disturbed more by all-terrain vehicles than by joggers. The observations of flocks presented here, from two long bridges with intensive traffic that crosses the lagoon, were always at a distance of at least 150 m, despite the shallow bottoms having similar morphological characteristics closer to the bridges.…”