Effects of Plant Cover Improvements for Nesting Ducks on Grassland Songbirds

Abstract

Filion. 2003. Effects of plant cover improvements for nesting ducks on grassland songbirds. Canadian Field-Naturalist 117(2): 167-172.Several islands located along the St. Lawrence River in southern Quebec have been used as natural pastureland by cattle for decades. Recently, a rest-rotation grazing system and dense nesting cover were established on four islands near Varennes to improve duck nesting conditions. The effects of these two plant cover improvements on the abundance of grassland songbirds were assessed through four treatments: (1) idle fields with no vegetation improvement but exclusion of cattle (IDLE), (2) improved pastures with seeding of forage plants for cattle (IMPP), (3) dense seeded nesting cover fields improved for ducks and where cattle were excluded (DNC), and (4) natural or unimproved pastures grazed by cattle after the duck nesting season (UIPP). The overall abundance of birds was similar among treatments before cover improvements as well as two years after. The abundance of Bobolinks (Dolichonyx oryzivorus) was significantly greater in DNC and UIPP two years after treatments while Red-winged Blackbirds (Agelaius phoeniceus) were more abundant in DNC and IDLE. Plant cover improvements had little impact on Savannah Sparrow (Passerculus sandwichensis) abundance. Furthermore, few annual or treatment-related changes were observed for less abundant species. On the short-term, duck nesting cover improvements in natural pastures did not have any major effect on grassland songbirds on Varennes islands.

Territory Selection by Upland Red-Winged Blackbirds in Experimental Restoration Plots

“…Bollinger (1995) found a positive relationship between presence of grass and blackbirds, and Camp and Best (1994) found a positive relationship between grass cover and nest densities. Other studies have shown that Red-winged Blackbirds favor dense vegetation (LaPointe et al 2003); Albers (1978) found that blackbird territories had significantly taller, denser vegetation than unused areas, and Bollinger (1995) found that Red-winged Blackbirds were most abundant in fields with dense cover. However, in a survey of Illinois grassland species, Herkert ( 1 994) found no correlates of vegetation structure and occupancy by Red-winged Blackbirds, which were present on 93% of his transects, and Scott et al (2002) found that blackbirds were negatively associated with grass cover on reclaimed surface mines in Indiana.…”

“…near the Missouri River. Numerous researchers have investigated habitat selection by Red-winged Blackbirds (Albers 1978, Joyner 1978, Pribill and Pieman 1997, Turner and McCarthy 1998, and some have examined responses of Red-winged Blackbirds and other species within plots characterized by differing management regimes (Herkert 1994, McCoy et al 2001, LaPointe et al 2003; however, our study is the only one we know of in which more than one factor varied (i.e., perch availability and grass cover) among adjoining treatment plots within the same sites. These plots varied with respect to densities of planted trees, which blackbirds used as perches, and the presence or absence of a planted cover crop.…”

Effects of grazing strategy on facultative grassland bird nesting on native grassland pastures of the Mid-South USA

“…In Oklahoma however, though field sparrow nests in PBG treatment pastures were fewer than in traditional control grazing pastures, the effects were not significant and overall success (17.6%) was comparable to reported ranges ( Holcomb, Davis & Fuhlendorf, 2014 ). Finally, red-winged blackbird nest densities were greater in idle and cattle exclusion treatment fields, than in those that included experimental disturbances ( Lapointe et al, 2003 ). Even thought we did not document a treatment effect indigo bunting DSR, our results were similar to previous reported DSR (∼93–96%) ( Weldon, 2006 ).…”