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Providing evidence to improve practice

Action: Employ grazing in natural grasslands Bird Conservation

Key messages

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  • Five of 12 studies from the USA and Canada, four replicated, found that some species studied were found at higher densities on grazed than ungrazed sites. Eight studies from the USA, Canada and France, six replicated, found that some or all species studied were found at lower densities on grazed sites compared to ungrazed sites or those under other management, or that there were no differences.
  • Two controlled studies from the USA and Canada, one replicated, found that duck nesting success was higher on grazed than ungrazed sites. Two studies from the USA found that songbird nesting success was lower on grazed than ungrazed sites. Three replicated and controlled (one randomised) studies from the USA and Canada found that grazing had little or no effect on nesting success in a variety of species.

 

Supporting evidence from individual studies

1 

At Union Slough National Wildlife Refuge, Iowa, USA (Burgess et al. 1965), a replicated, controlled trial in 1959-1961 found that blue-winged teal Anas discors nests in grazed grasslands and hayfields had greater success rates than those in ungrazed areas (47% success for grazed areas vs. 46% in hayfields and 14% in ungrazed areas; a total of 111 nests were monitored). However, nesting density was higher in ungrazed areas (7 nests/ha) than in grazed areas (4 nests/ha) or hayfields (4/ha). Areas were moderately grazed (15 June-1 October), ungrazed, or hay-cut (July-August, after the main nesting period).  Most nests were in Kentucky bluegrass Poa pratensis and alfalfa Medicago sativa.

 

2 

A replicated controlled study at three grassland sites in North Dakota, USA (Bowen & Kruse 1993), found that upland sandpiper Bartramia longicauda nesting density was lower in areas grazed by cattle during the nesting season, but there was little evidence that grazing treatments outside the breeding season influenced nest success. From 1981 to 1987, cattle grazing treatments were each applied to a field in each of the three study areas: spring grazing, autumn grazing, autumn-and-spring grazing, season-long grazing, and ungrazed.

 

3 

A randomised, controlled, replicated before-and-after study in 1980-1988 in mixed-grass prairie at Lostwood National Wildlife Refuge, North Dakota, USA (Kruse & Bowen 1996), found that nest densities of gadwall Anas strepera and blue-winged teal were lower in areas and years with spring cattle grazing, or a combination of grazing and summer burning compared to control areas. Five other species did not show a response to grazing. Nest success was generally high (31-45%) and unaffected by treatment. The authors argue that grazing reduced brush cover that provided nesting habitat for ducks.

 

4 

A paired site comparison in 1997-1999 at the Audubon Research Ranch and Davis Pasture in Arizona, USA (Gordon 2000), found no consistent effects of grazing grasslands on Ammodramus sparrow species. Baird’s sparrows A. bairdii were more abundant on the grazed than ungrazed area in 1997 (1.3 vs. 0.5 captures/plot/day) but did not differ significantly thereafter (0.4-1.9 vs. 0.8-1.3). Grasshopper sparrows A..savannarum were more abundant on the grazed area in 1997 (4.7 vs. 0.44), but more abundant on the ungrazed area in 1998 and 1999 (1.3-4.8 vs. 3.2-15.0). The Audubon Research Ranch (3,160 ha) was ungrazed by livestock since 1968, the Davis Pasture (1,501 ha) had moderate grazing pressure (645-1,387 animal unit months/year).

 

5 

A replicated, controlled trial in May-June 1995-1996 in grasslands in Prairie Ridge State Natural Area, Illinois, USA (Walk & Warner 2000), found that both native and non-native grasslands held higher average densities of five songbird species when under light, late-season grazing than when mown, ‘hayed’, unmanaged or burned (non-native grasslands only). However, species showed individual responses to different managements. The species surveyed were eastern meadowlark Sturnella magna and dickcissel Spiza americana, Henslow’s sparrow Ammodramus henslowii, field sparrow Spizella pusilla and grasshopper sparrow.

 

6 

A site comparison study in the Pyrénées-Orientales, France, in 1998-1999 (Pons et al. 2003), found that four bird species with an unfavourable conservation status in Europe preferentially used burned hillsides, compared with unmanaged or grazed areas. This study is discussed in detail in ‘Use prescribed burning’.

 

7 

A study in 2002-2003 in a grassland in Kentucky, USA (Sutter & Ritchison 2005) found that grasshopper sparrows had significantly lower nesting success on a grazed grassland, compared to a mown one (estimated 25% success on cattle-grazed area vs. 70% on mown area). This study is discussed in detail in ‘Mow or cut natural grasslands’.

 

8 

A replicated study in 2000-2002 on 34 fields of dry, native, prairie in southern Alberta, Canada (Koper & Schmiegelow 2007), found that grazing only affected six of 31 bird species investigated. Only soras Porzana carolina were more abundant in late-grazed fields than ungrazed fields, only marsh wrens Cistothorus palustris were more abundant in early-grazed fields compared to late-grazed and only lesser scaup Aythya affinis were more abundant in late-grazed fields than in those grazed early in the season.

 

9 

A replicated study using 23 years of data (up to 2003) from a tallgrass prairie in Kansas, USA (Powell 2006), found that three of seven species showed a significant response to grazing by American bison Bos bison: upland sandpipers and grasshopper sparrows were consistently more abundant on grazed sites, whilst Henslow's sparrows were almost absent. Dickcissel, eastern meadowlark, Bell's vireo Vireo bellii (a shrub-dependent species) and brown-headed cowbird Molothrus ater showed no significant response.

 

10 

A replicated study in 2000-2002 in 32 mixed-grass prairie fields in southern Alberta, Canada (Koper & Schmiegelow 2007), found that duck nesting success was influenced by grazing and vegetation structure (with higher nesting success in taller vegetation). Duck success was 43% lower in ungrazed fields compared with those grazed from July and northern shovellers Anas clypeata had 64% lower success in early-grazed fields, compared with those grazed from July. However, nesting success of all but one songbird species was not influenced by these factors. The authors conclude that managing for ducks using grazing and other interventions is unlikely to provide habitat for songbirds.

 

11 

A study in Oklahoma, USA, in 2003-2004 (Churchwell et al. 2008), found that dickcissel reproductive success was lower in grazed and burned pastures compared to on tallgrass prairie managed by patch-burns. This study is discussed in detail in ‘Use prescribed burning’.

 

12 

A replicated study in 2002-2003 (Powell 2008) at the same tallgrass prairie site in Kansas, USA, as in (9), found that three of seven species surveyed showed significant responses to low-intensity cattle grazing: upland sandpipers, grasshopper sparrows, and eastern meadowlarks were more abundant in grazed areas, whilst Henslow's sparrow, dickcissel, brown-headed cowbird (all grassland species) and Bell's vireo showed no response.

 

Referenced papers

Please cite as:

Williams, D.R., Child, M.F., Dicks, L.V., Ockendon, N., Pople, R.G., Showler, D.A., Walsh, J.C., zu Ermgassen, E.K.H.J. & Sutherland, W.J. (2018) Bird Conservation. Pages 95-244 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2018. Open Book Publishers, Cambridge, UK.