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Providing evidence to improve practice

Action: Employ grazing in artificial grasslands/pastures Bird Conservation

Key messages

Read our guidance on Key messages before continuing

  • Of ten studies captured, one replicated, controlled study from the USA found lower species richness in grazed areas than ungrazed. Another replicated, controlled study from the USA found no consistent differences in community composition between grazed and ungrazed areas.
  • A small study from Canada found an increase in duck populations following the start of grazing amongst other interventions.
  • Five studies from the UK and USA, four replicated, found higher use of, or higher nesting densities in, grazed areas compared to ungrazed. Seven studies from the UK, Canada and the USA, five replicated, found no differences in use or nesting densities, or lower abundances of birds on grazed, compared with ungrazed areas. One found that several species appeared to be excluded by grazing.
  • Three studies from the UK, USA and Canada, two replicated, found that nesting success or productivity was similar, or lower, on grazed sites compared with ungrazed.

 

Supporting evidence from individual studies

1 

A controlled study in 1980-1982 on the river Roding in Essex, England (Raven 1986), found that flood pasture alongside a 1.2 km stretch of the river with grazed ‘flood beams’ (see ‘Use environmentally sensitive flood management’) held a similar density of territories to an adjacent 1.8 km stretch which was not grazed (8-13 territories/km for grazed stretch vs. 6-21 territories/km for ungrazed). Riparian species (sedge warbler Acrocephalus schoenobaenus, Eurasian reed warbler A. scirpaceus and reed bunting Emberiza schoeniclus) were largely confined to the ungrazed section, whilst channel-nesting species (little grebe Tachybaptus ruficollis and common moorhen Gallinula chloropus) were at similar densities in both stretches.

 

2 

A series of replicated controlled trials on grassland sites at two reserves in Essex, England, between 1990 and 1992 (Vickery et al. 1994) found that brent geese Branta bernicla did not graze at higher densities on plots that were areas grazed, compared to cut and grazed areas, or areas that were just cut. Goose grazing intensity was not affected by sheep grazing compared to cattle grazing. Six replicates of each treatment were used.

 

3 

A small before-and-after study from May-July in 1992-1994 in river islands in Quebec, Canada (Lapointe et al. 2000), found that the number of dabbling ducks Anas spp. nesting in the area had increased from 143 to 263 nests following the establishment of rotational grazing and dense nesting cover (see ‘Plant wild bird seed or cover mixture’). However, fewer nests than expected by an even distribution across habitats were found in unimproved or improved pasture in 1993. More nests than expected were found in unimproved and fewer than expected in improved pasture in 1994. Nests on improved pasture had significantly lower success than those in other habitats (15% success of 39 nests vs. 47-82% elsewhere), with 33% being trampled. Nests on unimproved pasture had similar success rates (68% of 71 nests) to other habitats. Nesting densities were no higher on grazed pastures areas than other habitat types, and were lower than on areas seeded with dense nesting cover see (‘Plant wild bird seed or cover mixture’).

 

4 

A replicated controlled study in Washington County, Pennsylvania, USA, found that cattle-grazed stream-side riparian pasture had lower bird species richness and abundance than ungrazed areas (Popotnik & Giuliano 2000). Birds, nests and vegetation were surveyed along 12 pairs (grazed and control) of streams in 1996 and ten pairs in 1997. Several wetland-riparian species (e.g. common snipe Gallinago gallinago, green-backed heron Butorides striatus and solitary sandpiper Tringa solitaria) were more frequent or only occurred in controls. The authors suggest differences are largely due to simplified vegetation structure and reduced cover. Nest densities were higher in controls and nest destruction by cattle occurred in grazed areas, although nest success (all species combined) was not affected by grazing.

 

5 

A controlled before-and-after trial in 1981-1986 in Arapaho National Wildlife Refuge, Colorado, USA (Stanley & Knopf 2002), found few differences in overall bird density changes between two lightly grazed and two ungrazed pastures. However, for three of the nine species studied in detail, and for all three guilds examined, there were differences between treatments. Red-winged blackbirds Agelaius phoeniceus and American robins Turdus migratorius increased more on grazed pastures, as did species able to tolerate a moderate range of environmental conditions. However, willow flycatchers Empidonax traillii and species able to tolerate either a wide range of conditions or a very narrow range may have increased more on ungrazed pastures. The authors note that evidence for changes in most species was weak. The grazed pastures were grazed in August and September (with 2.4-3.5 animal-unit-months/ha) and then rested for 34 month.

 

6 

A before-and-after study at South Stack RSPB Reserve, Anglesey, Wales (Ausden & Bateson 2005), found that red-billed chough Pyrrhocorax pyrrhocorax use of 26 ha of semi-improved grassland increased following the introduction of year-round cattle grazing in spring 2002. In winter and spring, cattle density was typically less than 1/ha, rising to 2.5/ha during summer. Monitoring undertaken from November 2001 to August 2003, revealed that grazing also greatly reduced sward height.

 

7 

A replicated, controlled, paired sites study of wet pasture in Leicestershire, UK (Defra 2007), found that bird visit rates were significantly higher in areas with livestock than in those where livestock had been excluded.  Sampling involved 45 minute bird observations between April 2005-March 2007 (twice/month April-October; once/month November-March).

 

8 

A randomised, replicated controlled study in upland fields sown with a grass-legume mix at Los Banos Wildlife Area, California, USA (Carroll et al. 2007), found that dabbling ducks Anas spp. nested at higher densities in four grazed plots than four ungrazed plots in 1996 (2.2 nests/ha vs. 0.6/ha) but not 1997 (0.7/ha vs. ungrazed 0.4/ha). Nest success estimates did not significantly differ between grazed (5%) and ungrazed (3%) fields. In 1994, four 10-14 ha upland fields were seeded with a grass-legume mix. In 1995, each was divided in half by electric fencing and randomly assigned to rotational grazing (1 July-1 November) or ungrazed. Grazed fields had shorter vegetation than ungrazed fields through the winter, but by the start of the nesting season (late March) vegetation height did not differ. By the end of the nesting season (late May) grazed fields had taller vegetation.

 

9 

A replicated trial in the UK (Vale & Fraser 2007) found that songbirds and invertebrate-feeding birds were recorded more often on semi-natural rough grazing than on upland improved pasture, but the opposite was true for corvids. This study is discussed in detail in ‘Graze non-grassland habitats’.

 

10 

A replicated site comparison study on 1,031 agricultural sites across England in 2004-2008 (Ewald et al. 2010) found that investigated the impact of rough grazing on grey partridge Perdix perdix. However, the study did not distinguish between the impacts of grazing, scrub control and the restoration of various semi-natural habitats. There was a negative relationship between the combined intervention and the ratio of young to old partridges in 2008. This study describes the effects of several other interventions, discussed in the relevant sections.

 

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.