Methodology:

Global position system (GPS) devices were attached dorsally using marine Tesa tape to 346 wandering albatrosses (175 males, 171 females; full details in Weimerskirch et al. 2018; Weimerskirch et al. 2020). Birds were captured at the nest during the incubation period (January to April) of 2010 to 2020 from a colony on Possession Island (Crozet Islands archipelago, Southern Indian Ocean, 46°24'S, 51°46'E). The temporal coverage of the resulting GPS data for each year 2010-2020 can be viewed in the 'Temporal Coverage' section below.

The breeding success of each pair in the study colony was recorded as part of long-term monitoring and was defined as a binary variable, where 'SUCCESS' indicates that the chick survived to fledging, and 'FAILURE' indicates failure at the egg or chick stage. One value was recorded per pair per year for the years 1965-2020.

Boldness was measured as the reaction to the approach of a human observer (see Patrick, Charmantier, and Weimerskirch 2013 for full details). The observer noted each bird's behaviours as they approached from a 5-m distance, stopping short of reaching the bird itself. Behaviours were recorded using a 5-point ordinal scale ranging from 0 to 4, where 0 = no response; 1 = bird lifts head; 2 = bird rises onto tarsi; 3 = bird vocalises; 4 = bird stands up. Using this scale, higher scores indicate bolder birds. Using these measurements, boldness was estimated by extracting individual-level best linear unbiased predictors (BLUPs) from an ordinal generalised linear mixed model (GLMM) that was fitted to boldness scores using the R package MCMCglmm (Hadfield 2010). The model has been used in previous studies of this population (Patrick, Charmantier, and Weimerskirch 2013; Gillies et al. 2023), and full details on the methodology can be found therein. The model included the fixed effects of observation number and observer ID (typically one observer per year), a random intercept for individual ID, and a random effect for the additive genetic variance, represented as the matrix of pairwise relatedness amongst all individuals.

The sex of most birds was determined by behavioural observations (i.e. copulatory position when present with the partner or pre-laying attendance), structural size, plumage differences, or molecular sexing based on blood sampling (Fridolfsson & Ellegren, 1999).

Data collection:

Global positioning system (GPS) loggers: IgotU 120/600, Mobile Action Technology, weighing up to 32g; X-GPS and Centurion, Sextant Technology, NZ weighing 60-75g.

Data quality:

GPS data were filtered using an iterative forwards/backwards speed filter to remove points with flight speeds of > 80km h-1.

Where data were not available, the value 'NA' has been used.