Foraging behaviour and fuel accumulation of capital breeders during spring migration as derived from a combination of satellite‐ and ground‐based observations

Abstract

The migration strategy of many capital breeders is to garner body stores along the flyway at distinct stopover sites. The rate at which they can fuel is likely to be strongly influenced by a range of factors, such as physiology, food availability, time available for foraging and perceived predation. We analysed the foraging behaviour and fuel accumulation of pink-footed geese, an Arctic capital breeder, at their mid-flyway spring stopover site and evaluated to what extent their behaviour and fuelling were related to physiological and external factors and how it differed from other stopovers along the flyway. We found that fuel accumulation rates of geese at the mid-flyway site were limited by habitat availability rather than by digestive constraints. However, as the time available for foraging increased over the stopover season, geese were able to keep constant fuelling rate. Putting this in perspective, geese increased their daily net energy intake along the flyway corresponding to the increase in time available for foraging. The net energy intake per hour of foraging remained the same. Geese showed differences in their reaction to predators/disturbance between the sites, taking higher risks particularly at the final stopover site. Hence, perceived predation along the flyway may force birds to postpone the final fuel accumulation to the last stopover along the flyway. Flexibility in behaviour appears to be an important trait to ensure fitness in this capital breeder. Our findings are based on a new, improved method for estimating fuel accumulation of animals foraging in heterogeneous landscapes based on data obtained from satellite telemetry and habitat specific intake rates.Because some animals use stored fat and protein as an important energy source during their migration and breeding, studying their foraging behaviour and fuel accumulation is necessary in order to understand their migratory behaviour (Sapir et al. 2011). Arctic-nesting birds migrating in steps have a limited time to prepare for migration and subsequent breeding because the time window where conditions are suitable at each stopover site as well as for breeding is short (Ankney and MacInnes 1978, Alerstam and Lindström 1990, Prop and Black 1998, Drent et al. 2003. A common migration strategy is therefore to garner body stores along the flyway at distinct stopover sites in order to commence breeding soon after arrival -a strategy called capital breeding Daan 1980, Klaassen et al. 2006a). Stopover sites should provide sufficient food to allow for refuelling during their stay (Bauer et al. 2006). However, the optimal foraging conditions for the animals are limited in time and space and therefore the strategy they should employ in order to forage optimally is likely to depend on a range of factors whose importance may vary within a stopover season as well as among different stopover sites along the migratory route.

Scaring as a tool to alleviate crop damage by geese: Revealing differences between farmers’ perceptions and the scale of the problem

“…Hence, we consider dropping counts a good proxy for goose use of specific fields and indicative of direct reductions in subsequent yields. We show that goose grazing intensity declined with distance to goose roosts, which is in accordance with earlier studies (Jensen et al 2008 , 2016 ; Chudzińska et al 2016 ). Hence, it is expected that crop damage will also decrease with distance to roosts.…”

“…We only used data from grass pastures because the sample size for new-sown cereal fields was too low, given that most farmers had not sown cereals by the time of the survey. We used ArcGIS to measure the distance between each field and the nearest roosting site (see Chudzińska et al 2016 for an overview of roosts). All statistical analyses were calculated in R version 2.14.0 (R Development Core Team 2013 ).…”

Shooting may aggravate rather than alleviate conflicts between migratory geese and agriculture

“…Our scenarios have shown that shooting can have counterintuitive effects that increase rather than alleviate agricultural damage as compensation behaviours may make management measures inefficient or futile. Predictions of expected agricultural damage varied substantially between our scenarios: Considering a digestive efficiency of 54% and an energy content of 1 g dry matter grass of 17.8 kJ (Chudzińska, Nabe‐Nielsen, Nolet, & Madsen, ), increasing shooting intensity in NL increased the average cumulative per capita consumption in NL from c . 4.8 kg dry matter to 6.1 kg; increasing shooting/hunting intensity in Nenetskii oblast increased consumption in NL even more to 7.5 kg dry matter.…”

Yield reductions in agricultural grasslands in Norway after springtime grazing by pink‐footed geese

“…Per capita grazing pressure for geese will also differ between winter and spring, because while overwintering geese forage for maintenance and survival, their food intake in spring increases considerably in order to build up body reserves for the flight to Svalbard and for breeding (Black, Deerenberg & Owen 1991;Prop & Black 1998;Drent et al 2003). Chudzi nska et al (2016) found that, although net energy intake obtained per hour of actual foraging did not differ between foraging sites in Denmark and central Norway, the increase in daylength and hence time available for foraging in Norway made the net energy intake per day 50% higher in spring.…”