Density and Diversity of Overwintering Birds in Managed Field Borders in Mississippi

Abstract

Grassland bird populations are sharply declining in North America. Changes in agricultural practices during the past 50 years have been suggested as one of the major causes of this decline. Field-border conservation practices encouraged by the U.S. Department of Agriculture's National Conservation Buffer Initiative meet many of the needs of sustainable agriculture and offer excellent opportunities to enhance local grassland bird populations within intensive agricultural production systems. Despite the abundant information on avian use of, and reproductive success in, strip habitats during the breeding season, few studies have examined the potential value of field borders for wintering birds. We planted 89.0 km of field borders (6.1 m wide) along agricultural field edges on one-half of each of three row crop and forage production farms in northeastern Mississippi. We sampled bird communities along these field edges during February-March 2002 and 2003 using line-transect distance sampling and strip transects to estimate density and community structure, respectively. We used Program DISTANCE to estimate densities of Song (Melospiza melodia). Savannah (Passerculus sandwichensis), and other sparrows along bordered and non-bordered transects while controlling for adjacent plant community. Greater densities of several sparrow species were observed along most bordered transects. However, effects of field borders differed by species and adjacent plant community types. Diversity, species richness, and relative conservation value (a weighted index derived by multiplying species-specific abundances by their respective Partners in Flight conservation priority scores) were similar between bordered and non-bordered edges. Field borders are practical conservation tools that can be used to accrue multiple environmental benefits and enhance wintering farmland bird populations. Provision of wintering habitat at southern latitudes may influence population trajectories of short-distance migrants of regional conservation concern.

Breeding Bird Response to Field Border Presence and Width

“…Whereas most conservation buffers are restricted to riparian zones, CP33-Habitat Buffers for Upland Birds (hereafter, field borders) are non-crop, linear strips of herbaceous vegetation that target grassland birds in upland habitats (Burger et al 2006). Field borders benefit the avian community year-round by providing nesting habitat, foraging habitat, roosting sites, movement corridors, and escape cover (Marcus et al 2000, Conover 2005, Smith et al 2005, Conover et al 2007). The contribution of herbaceous strips to adjacent plant communities may also enhance avian benefits on agriculture-wooded field ecotones, where avian abundances are typically elevated (Best et al 1990).…”

Quantifying the contribution of birds to the control of arthropod pests on kale,Brassica oleracea acephala, a key crop in East African highland farmland

“…Linking increases in crop production with reductions in pest densities by birds could provide a strong economic incentive for farmers to undertake management actions that promote the abundance of key species of birds; for example, management that enhances vegetation complexity (Greenberg et al 2000;Perfecto et al 2004) and/or presence of non-cropped habitats (e.g. McLaughlin and Mineau 1995;Gurr et al 2003;Smith et al 2005).…”

On reversing the northern bobwhite population decline: 20 years later

“…One such example of policy and conservation alignment is the Conservation Reserve Program practice, CP33‐Habitat Buffers for Upland Gamebirds. Studies suggest that CP33 is producing positive population responses from bobwhites (Puckett et al 2000, Smith et al 2005 a , b ). Other opportunities exist to align Farm Bill policy and conservation initiatives (e.g., CP36‐Longleaf Pine [ Pinus palustris ] Initiative).…”