Within-pair similarity in migration route and female winter foraging effort predict pair breeding performance in a monogamous seabird

Abstract

In long-lived monogamous animals, pair bond strength and durability are usually associated with higher fitness. However, whether pairs maximise fitness during the non-breeding season by maintaining contact during the winter or, instead, prioritise individual condition is unclear. Using geolocators recording spatial (light) and behavioural (immersion) data, we tracked pairs of the long-term monogamous Atlantic puffin Fratercula arctica during the non-breeding season to determine whether and how migratory strategies were related to future pair breeding performance and whether within-pair similarity in migratory movements or individual behaviour best predicted future fitness. While pair members migrated separately, their routes were similar in the first part of the non-breeding season but diverged later on; nonetheless, pairs showed synchrony in their return to the breeding colony in spring. Pairs following more similar routes bred earlier and had a higher breeding success the following spring. However, female (but not male) winter foraging effort was also a strong predictor of subsequent fitness, being associated with future timing of breeding and reproductive success. Overall, females had higher daily energy expenditure than males, especially in the late winter when their route diverged from their partner's and they foraged more than males. Our study reveals that female winter foraging, probably linked to pre-breeding condition, may be more critical for fitness than maintaining the pair bond outside of the breeding season. However, even without contact between mates, pairs can benefit from following similar migration routes and synchronise their returns, but the mechanisms linking these processes remain unclear.

Linking oceanographic conditions, migratory schedules and foraging behaviour during the non‐breeding season to reproductive performance in a long‐lived seabird

“…The foraging behaviour during the non‐breeding season also differed between sexes. To our knowledge, only one study reported different at‐sea foraging activity between sexes in a migratory seabird species (Fayet, Shoji, Freeman, Perrins, & Guilford, ). We found that females tended to have higher foraging activity (i.e.…”

Using time-series similarity measures to compare animal movement trajectories in ecology

“…This ensures all trajectories start at the same point [0, 0] and standardized trajectories will be invariant to scaling and shifting (see Giao and Ahn 2016). We did not standardize coordinates when calculating NND in order to mirror the approach used in the previous ecological studies that used this measure (Fayet et al 2016(Fayet et al , 2017Shoji et al 2016;Votier et al 2017). When calculating LCSS and DTW we set δ to unlimited.…”

“…For example, most trajectory similarity studies in ecology use nearest neighbour distance (NND) (e.g. Freeman et al 2010;Demšar et al 2015;Fayet et al 2017;Votier et al 2017), but use of other trajectory similarity measures is rare. Moreover, in a recent review of metrics for ecological movement data (Seidel et al 2018) none of the similarity measures described here was mentioned yet they are routinely used in other fields.…”

Rhinoceros Auklet pair‐mates migrate independently but synchronize their foraging activity during the pre‐laying period

“…, Fayet et al . ). In sedentary species, it would be relatively easy to coordinate pair activities from the onset of breeding, as mates can stay together in their local home‐ranges during the non‐breeding period (e.g.…”

“…In long-lived monogamous bird species, pairs can maintain their bond for several years, which is important for successful breeding (Pyle et al 2001, S anchez-Macouzet et al 2014. During the breeding season, coordinated activities between mates contribute to the maintenance of pair bonds and thus probably enhance breeding success (Davis 1988, Spoon et al 2006, Mariette & Griffith 2012, S anchez-Macouzet et al 2014, Fayet et al 2017. In sedentary species, it would be relatively easy to coordinate pair activities from the onset of breeding, as mates can stay together in their local home-ranges during the non-breeding period (e.g.…”