Habitat preference of geese is affected by livestock grazing ‐ seasonal variation in an experimental field evaluation

Abstract

The number of staging geese in northwestern Europe has increased dramatically. Growing goose numbers put strong grazing pressure on agricultural pastures. Damage to agricultural land may be mitigated by managing nature reserves in order to optimally accommodate large numbers of grazing geese. Livestock grazing has been shown to facilitate foraging geese; we take the novel approach of determining the effects of four different livestock grazing treatments in a replicated experiment on the distribution of geese. We present experimental field evidence that livestock grazing of a salt marsh in summer affects the habitat preference of foraging geese during autumn and spring staging. In an experimental field set‐up with four different livestock grazing treatments we assessed goose visitation through dropping counts, in both autumn and spring. Grazing treatments included 0.5 or 1 horse ha‐1 and 0.5 or 1 cattle ha‐1 during the summer season. The livestock grazing regime affected goose distribution in autumn, just after livestock had been removed from the salt marsh. In autumn, goose visitation was highest in the 1 head ha‐1 grazing treatments, where grazing intensity by livestock was also highest. In line with this result, goose visitation was lowest in the 0.5 head ha‐1 livestock grazing treatments, where the grazing intensity by livestock was lowest. The differences in goose visitation among the experimental treatments in autumn could not be explained by the canopy height. In spring we did not find any effect of livestock grazing treatment on goose visitation. Differences in the distribution of geese over the experiment between autumn and spring may be explained by changes in the availability of nutrient‐rich vegetation. Livestock summer grazing with a high stocking density, especially with horses, can be used to attract geese to salt marshes in autumn and potentially reduces damage caused by geese to inland farmland. From a nature conservation interest point of view, however, variation in structure of the vegetation is a prerequisite for other groups of organisms. Hence, we recommend grazing of salt marshes with densities of 0.5 head ha‐1 of livestock when goose conservation is not the only management issue.

Effects of grazing management on biodiversity across trophic levels–The importance of livestock species and stocking density in salt marshes

“…We hypothesise that plant species richness benefits from higher stocking densities as grazing opens the canopy and decreases light competition (Borer et al, 2014). Such a short and open vegetation canopy will be beneficial for spring staging geese, as these small herbivores require high-quality forage (Mandema et al, 2014b). By contrast, protective cover for voles will decrease under high stocking densities (Villar et al, 2014), hence, voles are hypothesised to be more abundant under low stocking densities.…”

Dwarf shrub and grass vegetation resistant to long‐term experimental warming while microarthropod abundance declines on the Falkland Islands

“…and various grass species were grouped as the individual species were not consistently present across all 24 plots. However, this typically results in increased grazing by geese where cattle are present (Mandema et al 2014) while the opposite would have taken place on our study site as grass cover was consistently lower after 2003. have various causes, including overall deterioration of growth conditions or differences in annual productivity, with 2003 being particularly productive.…”

Spatial Diversity in Canopy Height at Redshank and Oystercatcher Nest-Sites in Relation to Livestock Grazing

“…ments than in the higher stocking density treatments, suggesting that breeding opportunities were more abundant in the low livestock treatments. Grazing by geese may fortify this effect, because geese prefer the high density grazed treatments in autumn, leading to an even greater homogenisation of the vegetation in the high density grazed treatments (Mandema et al 2014). Spatial variation in canopy height and average canopy height are known to be important in the nestsite choice of waders.…”

“…The area is important for a great number of breeding birds, mostly waders, and thousands of geese overwinter there. In autumn, the geese in the study area prefer high density livestock grazed sites (Mandema et al 2014). Therefore, in addition to livestock grazing, grazing by geese may affect spatial variation in canopy height.…”