Migrants and residents of a long‐lived seabird differ in their behavioural response to a stressor

Abstract

Inter‐individual variation in behaviour has been recognised as a major driver of population ecology, but its relationship to migratory strategy has been ill‐explored. Here, we investigated whether male migrant and resident Cory's shearwaters Calonectris borealis, a long‐lived partially migratory seabird, are distinguishable by their temperament at the colony. We tracked a large number of individuals over two winters using GLS devices and assessed whether exploratory behaviour and reaction to extraction from the nest corresponded to migratory strategy over this period. While exploratory behaviour was unrelated to migratory strategy, birds that were resident were more likely to be unreactive towards extraction from the nest. This difference in behavioural stress response, together with previous findings that migrants display higher physiological stress over winter, suggests that migrants and residents may be distinguishable by their stress threshold.

Accessible ecophysiological tools for seabird conservation

“…These overt signs of poor condition may be formed in response to acute stress events during feather development (King & Murphy, 1984; Jovani & Rohwer, 2017). Measuring the abundance and severity of fault bars could act as a proxy measure for individual condition, provided a standardized methodology is used (Gatt et al, 2021; Gatt, Granadeiro & Catry, 2021). Feather breakage from severe fault bars may impair flight efficiency if present in flight feathers (remiges, rectrices) by reducing the surface area of the wing (Navarro & González‐Solís, 2007), reducing foraging abilities or even likelihood of survival (Eggers & Low, 2014).…”

“…Birds that show a depressed stress response may be in critically poor condition, as they no longer have the capacity to respond to acute stressors (Rich & Romero, 2005). Reasons for increased or attenuated stress responses may vary and can be influenced by age (Heidinger, Nisbet & Ketterson, 2006; Elliott et al, 2014), developmental stress (Kitaysky et al, 2001a; Benowitz‐Fredericks, Schultner & Kitaysky, 2015), migratory strategy (Gatt, Granadeiro & Catry, 2021), or the reactivity of an individual to perceived stressors (Grace & Anderson, 2014). It is important to consider multiple lines of evidence when describing why CORT response patterns are seen in individuals or populations.…”