Individual study: Effect of summer sheep- versus summer cattle-grazing upon wintering brent geese Branta bernicula grazing intensity at Northey Island National Trust Nature Reserve, Essex, England
Vickery J.A., Sutherland W.J. & Lane S.J. (1994) The management of grass pastures for brent geese. Journal of Applied Ecology, 31, 283-290
In the UK, increasing numbers of wintering brent geese Branta bernicula feed inland where they cause damage to arable crops. However, there is little agricultural conflict when they graze on grass pasture and encouraging geese onto pasture is a way of reducing conflict between farmers and conservationists. Grazing intensity of brent geese was monitored over one winter on areas of grass pasture summer-grazed by either cattle or sheep on a nature reserve in southeast England.
Study site: The experiment was conducted at Northey Island National Trust Nature Reserve between April 1991 to April 1992. The field used was put down to grass in 1986 and managed sunsequently by cattle-grazing and cutting for silage.
Treatments: A random block design was set up in April 1991 with 12 plots of 50 m x 50 m and two treatments applied:
1) Grazed with 14 cattle over all six plots from 11 June to 30 August (186.7 Livestock Unit Days(LUD)/ha).
2) Grazed with six ewes from 11-29 August, an additional three per plot added on 24 June with two more on 4 July (to maintain a short sward). These additional sheep were removed on 22 August.
Goose grazing intensity: In the subsequent winter, goose grazing intensity was determined from dropping densities. At 10 random points (marked with a cane) per plot, droppings within 1.5 m of these (area 7.07 m²) were counted and cleared at 4-week intervals.
Sward height: Sward height was measured five times around each cane using a sward stick, and the average calculated. Sward height was measured at the beginning (November) and end (March) of the winter.
Vegetation analysis: In October, two 10 cm diameter cores of soil and vegetation were taken from each plot for chemical analysis.
Grazing intensity: Brent geese first arrived on the field in early October (1991), grazing until departure in early April. Grazing intensity was high in all plots but with no difference in intensity recorded.
Sward characteristics: There was no significant differences in sward height, tiller density, biomass of dicotyledons (primarily clover Trifolium spp.) or the live:dead ratio of grass. The biomass of live grass was significantly greater in cattle-grazed compared with sheep-grazed areas. Chemical analysis of the first two leaves of grass tillers (brent geese select young leaves) showed no significant difference in the protein (nitrogen) content of the grass.
Conclusions: Over the short duration of this study, the different summer grazing regimes appeared not to influence wintering brent goose grazing intensity. However, biomass of live grass was greater in the cattle-grazed areas.
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