Highly dynamic wintering strategies in migratory geese: Coping with environmental change

Abstract

When and where to move is a fundamental decision to migratory birds, and the fitness‐related costs and benefits of migratory choices make them subject to strong selective forces. Site use and migration routes are outcomes of opportunities in the surrounding landscape, and the optimal migration strategy may be conservative or explorative depending on the variability in the environment occupied by the species. This study applies 25 years of resighting data to examine development in winter migration strategy of pink‐footed geese divided among Denmark, the Netherlands and Belgium, and analyse potential drivers of strategy change as well as individuals’ likelihood to break with migratory tradition. Contrary with the general notion that geese are highly traditional in their winter site use, our results reveal that winter migration strategy is highly dynamic in this species, with an average annual probability of changing strategy of 54%. Strategy was not related to hunting pressure or winter temperature, but could be partly explained by a tracking of food resources in a landscape of rapid land use changes. The probability of individuals changing strategy from year to year varied considerably between birds, and was partly related to sex and age, with young males being the most likely to change. The annual probability of changing wintering strategy increased substantially from ≈40% to ≈60% during the study period, indicating an increasingly explorative behaviour. Our findings demonstrate that individual winter strategies are very flexible and able to change over time, suggesting that phenotypic plasticity and cultural transmission are important drivers of strategy choice in this species. Growing benefits from exploratory behaviours, including the ability to track rapid land use changes, may ultimately result in increased resilience to global change.

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

“…Second, we assumed that geese are “informed migrants”, that is, they “knew” conditions in all regions along the migration route and respond optimally to them. Although this might appear a strong assumption, several goose species have demonstrated a high capacity of swiftly responding to new conditions and adopting new migration patterns (Clausen, Madsen, Cottaar, Kuijken, & Verscheure, ). If this assumption is violated, our results would be a rather optimistic view (from a goose’ perspective) as consequences for migration and fitness will likely be much more severe if changes are unexpected (Klaassen et al., ).…”

Contrasting consequences of climate change for migratory geese: Predation, density dependence and carryover effects offset benefits of high‐arctic warming

“…However, the potential benefits of advanced phenology likely depend on the capacity of Arctic geese to align their migratory cues (Lameris et al, 2017), thereby avoiding trophic mismatch. In some Arctic species, migratory strategies are relatively dynamic (Clausen, Madsen, Cottaar, Kuijken, & Verscheure, 2018;Eichhorn, Drent, Stahl, Leito, & Alerstam, 2009;Lameris et al, 2017); however, migration timing is at least partially fixed (Kölzsch et al, 2015;Lameris et al, 2018;Van der Jeugd et al, 2009). The reliability of resources at spring stopover sites will also determine their ability to respond to future change (Fox et al, 2014;Prop, Black, & Shimmings, 2003).…”

Northward range expansion in spring‐staging barnacle geese is a response to climate change and population growth, mediated by individual experience

“…Behavioural responses are common, particularly in birds, and include adjustments in the timing of migration (Bauer, Van Dinther, Høgda, Klaassen, & Madsen, ; Kölzsch et al, ; Tombre et al, ) and egg laying dates (Both et al, ; Crick & Sparks, ). Moreover, birds' spatial distributions change in winter (Ambrosini et al, ; Barbet‐Massin, Walther, Thuiller, Rahbek, & Jiguet, ; Ramo et al, ), during breeding (Guillemain & Hearn, ; Huntley et al, ) and during migration (Clausen, Madsen, Cottaar, Kuijken, & Verscheure, ; Prop, Black, Shimmings, & Owen, ).…”

“…Alternatively, changes can result from individually or collectively adjusted migratory choices in direct response to a changing environment (Berdahl et al, 2018;Clausen et al, 2018). These choices may then be inherited and spread through the population via social learning, which provides the possibility of cultural evolution in addition to genetic evolution (Aplin, 2019).…”

“…New migration strategies in goose populations have previously been demonstrated to spread relatively fast within the population (Clausen et al, 2018;Eichhorn, Drent, Stahl, Leito, & Alerstam, 2009;Feige et al, 2008;Larsson, Forslund, Gustafsson, & Ebbinge, 1988). This may be attributed to individuals switching strategies in response to previous experiences, and additionally to social learning by juvenile and older geese.…”