Year-round activity levels reveal diurnal foraging constraints in the annual cycle of migratory and non-migratory barnacle geese

Performing migratory journeys comes with energetic costs, which have to be compensated within the annual cycle. An assessment of how and when such compensation occurs is ideally done by comparing full annual cycles of migratory and non-migratory individuals of the same species, which is rarely achieved. We studied free-living migratory and resident barnacle geese belonging to the same flyway (metapopulation), and investigated when differences in foraging activity occur, and when foraging extends beyond available daylight, indicating a diurnal foraging constraint in these usually diurnal animals. We compared foraging activity of migratory (N = 94) and resident (N = 30) geese throughout the annual cycle using GPS-transmitters and 3D-accelerometers, and corroborated this with data on seasonal variation in body condition. Migratory geese were more active than residents during most of the year, amounting to a difference of over 370 h over an entire annual cycle. Activity differences were largest during the periods that comprised preparation for spring and autumn migration. Lengthening days during spring facilitated increased activity, which coincided with an increase in body condition. Both migratory and resident geese were active at night during winter, but migratory geese were also active at night before autumn migration, resulting in a period of night-time activity that was 6 weeks longer than in resident geese. Our results indicate that, at least in geese, seasonal migration requires longer daily activity not only during migration but throughout most of the annual cycle, with migrants being more frequently forced to extend foraging activity into the night

Geese grazing grasslands: Managing the impact of geese on agricultural grassland

In recent years, many goose populations have increased substantially, potentially negatively affecting their natural environment and leading to conflict with farmers. To reduce farmer-goose conflict different management approaches are possible: compensation payments, scaring geese from certain areas to concentrate them in accommodation areas, or, when legally allowed, active population reduction. However, to effectively and ethically implement such practices, we need to understand how goose grazing affects agricultural yields and how management can influence this. This thesis looks at the effect of the timing and intensity of grazing on agricultural grassland through literature research, analysis of GPS-data and existing data on goose numbers and agricultural damages, and an experimental exclosure study. Furthermore, a simulation study is described, evaluating the potential cost-effectiveness of management through scaring and accommodation. We find that the effect of grazing on yield increases with grazing pressure, but at a decreasing rate. Temporal factors of grazing also play an important role in the effect of grazing on grassland yields. Grazing can change the growth rate of grass, delaying the start of the growing season and allowing yield losses to increase even after grazing ends. The effect of grazing differs between species, which has consequences for goose management. Scaring activities may have negative effects on goose survival and could result in higher economic costs associated with goose grazing. To be effective, the timing within the season and the required scaring intensity need to be carefully considered. Furthermore, adequate alternative habitat, suitable for multiple species, should be available

Geese grazing grasslands: Managing the impact of geese on agricultural grassland

In recent years, many goose populations have increased substantially, potentially negatively affecting their natural environment and leading to conflict with farmers. To reduce farmer-goose conflict different management approaches are possible: compensation payments, scaring geese from certain areas to concentrate them in accommodation areas, or, when legally allowed, active population reduction. However, to effectively and ethically implement such practices, we need to understand how goose grazing affects agricultural yields and how management can influence this. This thesis looks at the effect of the timing and intensity of grazing on agricultural grassland through literature research, analysis of GPS-data and existing data on goose numbers and agricultural damages, and an experimental exclosure study. Furthermore, a simulation study is described, evaluating the potential cost-effectiveness of management through scaring and accommodation. We find that the effect of grazing on yield increases with grazing pressure, but at a decreasing rate. Temporal factors of grazing also play an important role in the effect of grazing on grassland yields. Grazing can change the growth rate of grass, delaying the start of the growing season and allowing yield losses to increase even after grazing ends. The effect of grazing differs between species, which has consequences for goose management. Scaring activities may have negative effects on goose survival and could result in higher economic costs associated with goose grazing. To be effective, the timing within the season and the required scaring intensity need to be carefully considered. Furthermore, adequate alternative habitat, suitable for multiple species, should be available

De relatie tussen oogstvermindering en begrazingsdruk door ganzen – implicaties voor beheer

Nelleke Buitendijk discusses a newly published study from her and her colleagues on the impact of grazing on agricultural grasslands. Highlights include that decreasing herbivore abundance may not directly translate to a decreased yield loss, and that management tools should be used with care

Geese grazing grasslands: Managing the impact of geese on agricultural grassland

In recent years, many goose populations have increased substantially, potentially negatively affecting their natural environment and leading to conflict with farmers. To reduce farmer-goose conflict different management approaches are possible: compensation payments, scaring geese from certain areas to concentrate them in accommodation areas, or, when legally allowed, active population reduction. However, to effectively and ethically implement such practices, we need to understand how goose grazing affects agricultural yields and how management can influence this. This thesis looks at the effect of the timing and intensity of grazing on agricultural grassland through literature research, analysis of GPS-data and existing data on goose numbers and agricultural damages, and an experimental exclosure study. Furthermore, a simulation study is described, evaluating the potential cost-effectiveness of management through scaring and accommodation. We find that the effect of grazing on yield increases with grazing pressure, but at a decreasing rate. Temporal factors of grazing also play an important role in the effect of grazing on grassland yields. Grazing can change the growth rate of grass, delaying the start of the growing season and allowing yield losses to increase even after grazing ends. The effect of grazing differs between species, which has consequences for goose management. Scaring activities may have negative effects on goose survival and could result in higher economic costs associated with goose grazing. To be effective, the timing within the season and the required scaring intensity need to be carefully considered. Furthermore, adequate alternative habitat, suitable for multiple species, should be available

Timing and intensity of goose grazing:Implications for grass height and first harvest

Grazing birds like geese can have a big impact on agricultural land, potentially causing damage to crops. Their exploitation of agricultural land varies within and between seasons, and these temporal grazing patterns can be influenced by management. Furthermore, management practices using scaring and accommodation aim to influence local grazing pressures. To achieve efficient goose management we need a good understanding of the effects of timing and intensity of grazing on grass development and subsequent yield loss. We performed an exclosure study on twelve fields in Friesland (Fryslân), the Netherlands to study the effect of grazing on grass development and potential yield loss. Grazing was prevented either from November or from early April until farmers anticipated their first harvest. Every two weeks we measured grass height and calculated growth in exclosures and in ungrazed plots, and performed dropping counts. The results show that the difference in grass height between grazed and ungrazed plots increases with grazing pressure, but less so for higher grazing pressures. We also find that both winter and spring grazing can result in a larger difference in grass height between grazed and ungrazed plots, and grazing into the growing season delays the start of grass growth. This appears due to the relationship between grass height and growth rate. Because the optimal height for growth increases over the season, spring grazing has a much larger impact on grassland yields than winter grazing. Overall these results show that the amount of yield loss depends on different aspects of grazing, most prominently the recovery time, duration and grazing intensity. We hypothesize that barnacle geese may select fields with denser swards and may stimulate sward density by frequent grazing throughout winter and early spring as well as across consecutive years. Future studies should look into the effect of harvest delays and sward density on the size and quality of yield across the season and especially at the last cut. Management with scaring and accommodation may be able to reduce overall yield losses, but the effect may depend on the timing and location of scaring.</p