Preventing Crop Damage by Geese: Effectiveness of Different Scaring Techniques in Sweden

Abstract

Several goose species have increased in numbers in Europe and North America for more than five decades. This has posed conflict between agriculture and conservation. Scaring is a widely used damage mitigation tool to make agricultural fields less attractive to wildlife and to reduce crop damage. This study sought to investigate the effectiveness of different scaring techniques in preventing crop damages caused by geese in Sweden. For objective one, the effect of three different scaring devices (kite, scarecrow, inflatable man) on the number of geese in fields with cereals, ley, rapeseed, potatoes, and carrots were tested in south-central Sweden. Geese were counted by camera traps. Two approaches were used; in a first (model 1) only geese within 50– 150m of the scaring devices were counted, and in a second (model 2) all geese in the field were included. A total of 42,281 geese were counted: Greylag goose (Anser anser) was the most common species (87%), followed by bean goose (Anser fabalis) (6%), greater white-fronted goose (Anser albifrons) (3%), barnacle goose (Branta leucopsis) (2%), and Canada goose (Branta canadensis) (2%). The inflatable man decreased goose numbers by 90.0 %, scarecrow 64.6%, and kite 60.5%. A similar pattern was found in model 1, but the decrease was not significant. General Linear Mixed Models (GLMM) were used to evaluate the effect of the treatments on the number of geese in each trial. All analyses for this objective were performed in the statistical software R version 3.6.6. For objective two, literature review on ScienceDirect using the search terms "Geese" and "scaring was conducted." These terms were searched anywhere in the articles except in the references. The initial search yielded 223 results. However, 22 articles were inaccessible due to unavailability of authors, leaving us with 201 articles for further examination. To determine relevance, abstracts were scanned for indications of effectiveness and cost efficiency. Examination of full text was done for articles with relevant findings in the abstracts to extract data pertaining to the type of crop, season, methods employed, geographical region, the comparative efficacy of various scaring techniques, and the associated costs. Human bird scarers had 100% and inflatable man 90% scaring effect, but the cost of scaring was high when using inflatable man (364 USD) while kites had 60.5% and scarecrow had 64.5% scaring effect but were less costly (18.2 and 36.4 USD respectively). All analyses for this objective were performed in Microsoft excel. For objective three, scaring consultants employed by county administrative boards to help farmers deter geese from farms in 15 counties in Sweden (Dalarna, Gotland, Jämtland, Jönköping, Kalmar, Norrbotten, Örebro, Östergötland, Skåne, Södermanland, Uppsala, Värmland, Västerbotten, Västmanland, and Västra Götaland) were interviewed. Farmers were asked to rate the perceived effectiveness of commonly used scaring techniques for geese on a scale from 1 to 10. They provided assessments of the perceived duration of the scaring effect in terms of the number of days and the perceived cost efficiency of these techniques on a scale from 1 to 10. Fire crackers (4.6) and Lethal scaring (4.5) had the highest perceived effect, Exclosure river (3.7) and Inflatable man (3.2) had moderate effect and Rotating mirror pyramid (2.6) and Rotating mirror (2.4) had the lowest effect. All analyses for this objective were performed in Microsoft excel. This study showed that the scaring devices examined can reduce goose grazing pressure locally for some time. However, since geese continued to graze during scaring, its concluded that scaring alone is not enough to mitigate crop damage from geese. Future work to develop more effective control measures should address the efficiency of other management tools and scaring techniques, and in combination.