The Botteri's Sparrow and Exotic Arizona Grasslands: An Ecological Trap or Habitat Regained?

Abstract

The Botteri's Sparrow (Aimophila botterii) is a bird of tall grasslands that temporarily disappeared from Arizona following heavy livestock grazing in the 1890s. Its return was noted first in sacaton (Sporobolus wrightii), an uncommon native floodplain tallgrass often >2 m in height, and subsequently in stands of exotic lovegrasses (Eragrostis spp.) spreading into adjacent uplands that otherwise supported shorter native grasslands. We examined whether the exotic grasslands provided suitable breeding habitat for Botteri's Sparrows, compared to native grasslands. We counted birds for three years on 18 plots, monitored 314 nests on 323 home ranges, banded 583 birds, and measured vegetation on plots and home ranges, and at nests and fledgling locations. Abundance and site fidelity were positively associated with grass height and cover, being greatest in sacaton, intermediate in exotics, and lowest in native upland grasslands. The three habitats did not differ in young fledged per capita. Vegetation cover on Botteri's Sparrow home ranges did not differ from the surrounding available habitat, but locations of flightless recently fledged young included taller and more dense vegetation than either nest sites or random locations, especially in sparsely vegetated native grasslands. These results suggest that fledglings required substantial cover to avoid predation while they completed development. Far from being an ecological trap, the exotic lovegrasses apparently are providing essential cover for the Botteri's Sparrow in Arizona, perhaps allowing it to regain an abundance similar to what existed regionally prior to overgrazing of the late 19th Century.

Potential ‘Ecological Traps’ of Restored Landscapes: Koalas Phascolarctos cinereus Re-Occupy a Rehabilitated Mine Site

“…An interesting example of the association between restoration and ecological traps comes from the link found between particular native birds and invasive plant species. In the south-western United States, restoration projects that removed invasive plants created threats to native bird populations [55] , [56] . More generally, human-modified landscapes have previously been associated with population sinks and ecological traps [57] , [58] , [59] .…”

Songbird Use of Native and Invasive Fruit in the Northeastern USA

“…Finally, in addition to their value as food, invasive plants are also reported to affect nesting success for birds that use them as nesting substrates. Lower nest success for birds nesting in invasive plants has been reported from Illinois (Schmidt and Whelan 1999), Ohio (Borgmann and Rodewald 2004, Rodewald et al 2010) and Arizona (Jones and Bock 2005), USA. In contrast, studies from the Northeast indicate that the abundance of gray catbirds and American robins was positively related to the abundance of Lonicera fruit (Gleditsch and Carlo 2014), and breeding abundance of gray catbirds was positively correlated to the cover of invasive species in wildlife openings in Connecticut, USA (Mazzei 2009).…”

“…Invasive plants can be detrimental to populations of native vertebrates by altering vegetation characteristics and food availability in native landscapes (Tallamy 2004, Ortega et al 2006). For avian communities, the direct and indirect effects of plant invasions on habitat quality have been linked to reduced species abundance and diversity (Mills et al 1989, Germaine et al 1998, Hunter et al 1998) and lower reproductive success (Schmidt and Whelan 1999, Borgmann and Rodewald 2004, Jones and Bock 2005, Rodewald et al 2010). However, in some cases, invasive plants have been shown to provide important resources for native wildlife (Sax et al 2005, Schlossberg and King 2010, Meyer et al 2015).…”

Fledgling Bachman’s Sparrows in a longleaf pine ecosystem: survival, movements, and habitat selection

“…Fledgling Bachman’s Sparrows may select grass‐dominated patches intermixed with bare ground as reported for grassland songbirds (Jones and Bock 2005, Hovick et al 2011, Small et al 2015) or they may select patches with woody cover like fledgling songbirds in forests (King et al 2006, Ausprey and Rodewald 2011). Fledgling Bachman’s Sparrows might be assumed to select conditions similar to those selected by breeding adults, but fledglings may select areas with greater woody understory cover or greater woody stem density to provide escape cover or thermal cover.…”

“…The characteristics of high‐quality cover for fledglings vary among species and across land‐cover types, but fledglings in many species select habitat patches that maximize predator avoidance (Champlin et al 2009a,b, Vitz and Rodewald 2011, Streby and Andersen 2012) and food availability (Anders et al 1998, Kershner et al 2004, White et al 2005, Dittmar et al 2014, Streby et al 2015, Martinez et al 2019). For grassland‐dependent species, high‐quality cover for fledglings often consists of tall herbaceous vegetation, minimal amounts of litter, and moderate amounts of grass interspersed with bare ground (Jones and Bock 2005, Hovick et al 2011, Giovanni et al 2015, Small et al 2015). Grassland in the absence of fire or other disturbance may become increasingly dense and restrict ground mobility (Taillie et al 2015, Winiarski et al 2017b).…”