Ground nesting birds in roadside borders of the Argentine Pampas: habitat use and predation risk of artificial nests

Abstract

Habitat loss and fragmentation have led to grassland bird declines, with ground nesters particularly vulnerable. Roadsides could provide habitat, although their suitability depends on several roadside and field characteristics. Vegetation structure determines foraging and nesting site availability. In addition, road delimits sharp edges where the activity of nest predators is usually higher, whereas herbaceous vegetation determines ground nest concealment. Trees could provide lookouts to predators, and modified habitat and woodlands in surrounding fields could offer additional resources to predators. Our objective was to assess habitat suitability for ground nester birds in roadsides belonging to one modified grassland of the Argentine Pampas. We surveyed birds (90 plots) and monitored artificial nests (60 plots) in different road types: unpaved, paved of one-lane per side, and paved of two-lanes per side. Within each road type, we evaluated the relationship that ground nesters abundance had with vegetation structure of roadsides and surrounding fields. In addition, we related predation of artificial nests with the proximity to the road, roadside vegetation, and modified land and woodlands of surrounding fields. We made 2832 records of 84 species using roadsides, including 1083 records of 13 ground nesting species. Abundance of ground nesters increased with tall grass cover of roadsides and decreased with the number of native trees within roadsides. Roughly half (31/60) of the artificial nests were predated and 82.6% of the identified egg-marks were of mammal teeth. Nest predation decreased with nest proximity to the road. Our results emphasize the importance of tall grass cover of roadsides for the conservation of ground nesting species, and the necessity of monitoring natural nests in order to clarify the effect of trees, proximity to the road, and other environmental variables on nest success.

Location matters: survival of artificial nests is higher in small grassland patches and near the patch edge

“…Furthermore, we found an effect of distance to patch edge, with interior nests being more predated than edge nests. Although these results were contrary to our expectations, they are in accordance with the pattern recently found by Depalma and Mermoz (2019), who evaluated the effect of distance to a road on predation of artificial nests in the Pampas region. In our case, the main predators were small mammals (82.8% of predated nests).…”

“…tussock-scale). For southeastern South American grasslands, studies on artificial nests evaluated types of predators and, particularly, the effect of grazing (Cozzani & Zalba 2012), nest height (Cardoni et al 2012), fire intensity (Bahía & Zalba 2019), and proximity to a road and vegetation structure (Depalma & Mermoz 2019).…”

Interspecific interactions disrupted by roads

“…By contrast, some studies have found no effect (Huhta, 1995; Bechet, Isenmann & Gaudin, 1998; Mettenbrink, Dreitz & Knopf, 2006; Svobodová, Šálek & Albrecht, 2007) or a positive effect of road proximity on nest survival (Delgado García, Arévalo & Fernández‐Palacios, 2005; Angkaew et al ., 2019; da Silva et al ., 2019). Nest predation on road verges involves a complex interaction among: ( i ) the type of infrastructure, with nest predation higher near dirt roads (DeGregorio, Weatherhead & Sperry, 2014); ( ii ) roadside structure (Bergin, Best & Freemark, 1997; Shochat et al ., 2005), with perches such as trees increasing nest predation and tall grass reducing it (Depalma & Mermoz, 2019); ( iii ) traffic volume, with higher traffic loads decreasing nest predation relative to birds breeding close to medium‐to‐low‐traffic roads (Pescador & Peris, 2007); and ( iv ) predator traits, with human‐tolerant or bold predators showing increased foraging activity along road corridors (Pedersen et al ., 2011; Khamcha, Powell & Gale, 2018). However, it is necessary to point out that the literature on nest predation is largely dominated by studies on birds, with only two studies focused on another taxon (turtles).…”

Roadsides are key habitats for birds in the Argentine Pampas: conservation and management implications

“…Moreover, their roadsides are often unnecessarily mown, fumigated or even cropped to increase agricultural yields. Argentine Pampas' roadsides have a high conservation value: it has been reported that their vegetation is similar to the original vegetation of the region (Herrera et al 2017, Depalma & Mermoz 2019 and that they host great plant and pollinator diversity (Herrera et al 2020, Monasterolo et al 2020). In addition, birds are more frequent in field and road borders than in the adjacent fields (Leveau & Leveau 2011).…”