Modelling harvest of Greenland barnacle geese and its implications in mitigating human–wildlife conflict

Abstract

1. Arctic-breeding goose populations have increased in recent decades and their expansion into agricultural areas has caused increasing conflict with farmers due to the damage they cause. Lethal control and scaring are common management strategies of conflict mitigation. Management typically focuses on local/national scales, making addressing the impact of localised control on the wider population challenging, particularly when populations move over large areas and cross international borders.2. We construct an integrated population model (IPM) to assess the cumulative impact of all shooting harvest (hunting and derogation shooting) on the Greenland barnacle goose, Branta leucopsis. We use data from monitoring schemes throughout the migratory flyway and use population projections to evaluate the impact of potential future shooting strategies on abundance.3. Our model suggests flyway abundance has declined since its 2012 peak, consistent with an increase in harvest rate and low productivity. Harvest rate increase was most pronounced on Islay (rising from 2% to 7% from 2011 to 2017), suggesting this was a probable cause of flyway abundance decline. 4. Islay abundance has declined since derogation shooting began in 2000, while abundance at other wintering sites has increased. This may indicate that declines in Islay abundance may be due to both shooting mortality and emigration from Islay.5. Should future flyway-level harvest rates increase, further declines in abundance could be expected, and are likely to be more pronounced if harvests are extended to the entire winter range. Conversely, should harvest rates decline, an increase in abundance is predicted. Projections can therefore be used to allocate flywaylevel harvest rates to alleviate local pressure without hindering flyway-level management objectives.6. Synthesis and applications. Our findings demonstrate the impact of local harvests on global abundance, emphasising the importance of internationally coordinated monitoring and management strategies of migratory species. IPMs provide a | 765

Flying without fear: Shooting disturbance has little effect on site preferences in a conflict goose species

“…Social information likely influences habitat selection and predator avoidance and is affected by individual experience and group composition (Gil et al., 2018; Jones et al., 2017). On Islay, shooting intensity for the period of this study has been low with most fields experiencing less than five shooting disturbance events per winter (Figure 7); consequently, individuals experience little shooting disturbance per foraging site (McIntosh, 2022). Combined with high within‐flock turnover rates (especially in areas of high abundance such as near refuges), most flock members are likely naïve to field‐specific shooting disturbance risk (Simonsen et al., 2017), resulting in low ‘flock‐level’ perceived predation.…”

“…On Islay, shooting status is assigned at a field level according to its reseed status, creating a mosaic of small disturbance sites across the island within a matrix of improved grassland with low overall disturbance (Figure 1). While shooting is targeted at flocks on specific fields, the disturbance caused by a single shooting event is more widespread, extending to flocks foraging in the surrounding landscape (McIntosh, 2022). This may dilute the perceived disturbance/predation risk at specific sites as geese are exposed to shooting disturbance without reinforcement of mortality.…”

“…This creates a temporally unpredictable, low‐intensity shooting landscape with ample alternative foraging opportunities. Disturbance responses may be limited to short‐term redistributions to similar undisturbed fields and on‐site behavioural changes such as increased vigilance and intake rates (Bauer et al., 2018; Béchet et al., 2004) rather than stimulating changes in site selection at a winter scale (McIntosh, 2022). Thus, shooting disturbance may exacerbate local conflict if geese persist on high‐value reseeded fields, but increase foraging effort to offset the energetic costs of short‐term disturbance flights (de Jager et al., 2023; Nolet et al., 2016).…”

“…In this study, we used GPS tracking to highlight the importance of improved grassland and variability in selection within this key habitat for GBG wintering on Islay. While the aim of reducing the population has been achieved through the current management (McIntosh et al., 2023), a lack of distinctive response to shooting disturbance has implications for the effectiveness of the current shooting management strategy as a means of scaring. For scaring to be effective, shooting disturbance must create a significant perceived predation risk associated with targeted sites.…”