Fearfulness of geese and swans on cropland in winter: a multi‐species flight initiation distance approach

Geese and swans are focal species in conservation and in management aimed at reducing crop damage. In the former disturbance should be minimized, and in the latter it is important to know how different species react to scaring activities. Previous research about trade‐off between predation risk and foraging in birds often uses ‘flight initiation distance' (FID) as a proxy to compare fearfulness under different circumstances and among species. We studied variation in FID in geese and swans by species, flock size and composition, time of day, and body size (408 scaring trials on agricultural land in the winters 2018–2021). In single‐species flocks mean FID decreased in the order: bean goose (171 m) > greylag goose (104 m) > whooper swan (102 m) > Canada goose (92 m) > barnacle goose (77 m). In line with predictions based on body mass, the lightest species (barnacle goose) was the least fearful, but contrary to prediction neither of the two heaviest species (whooper swan, Canada goose) was the most fearful. FID was negatively correlated with flock size in bean goose. Flock size and FID did not correlate in greylag, Canada, and barnacle geese. FID did not differ between morning and afternoon in the four species with a sample of > 20 single‐species trials. When in multi‐species flocks, FID differed less among species, converging in the 108–138 m range. Accordingly, bean goose FID decreased significantly whereas it increased significantly in barnacle and greylag geese. Barnacle goose (protected from hunting by the EU Birds Directive) was less fearful than species with an open hunting season in the EU, implying that exposure to hunting affects species‐specific FID. We show that the level of fearfulness varied among swan and goose species, making it necessary to adopt diverse strategies in conservation as well as crop protection.