Age-related variation in non-breeding foraging behaviour and carry-over effects on fitness in an extremely long-lived bird

05 Jul 2018

1. Senescence has been widely documented in wild vertebrate populations, yet the 26 proximate drivers of age-related declines in breeding success, including allocation trade-27 offs and links with foraging performance, are poorly understood. For long-lived, 28 migratory species, the non-breeding period represents a critical time for investment in 29 self-maintenance and restoration of body condition, which in many species is linked to 30 fitness. However, the relationships between age, non-breeding foraging behaviour and 31 fitness remain largely unexplored. 32 2. We performed a cross-sectional study, investigating age-related variation in the foraging 33 activity, distribution and diet of an extremely long-lived seabird, the wandering albatross 34 Diomedea exulans during the non-breeding period, and its links with subsequent 35 reproductive performance. 36 3. We tracked the distributions of 82 adults aged 8 – 33 years with geolocator-immersion 37 loggers and found an age-related decline in the number of landings (a proxy of foraging 38 effort) during daylight hours. There was a decrease in body feather δ13C values in older 39 males but not females, yet this did not accompany an age-related shift in distributions. 40 Males conducted fewer landings than females, and the sexes were spatially segregated, 41 with males foraging further south, likely due to their differential utilization of winds. 42 4. While younger (< 20 years) birds had higher foraging activity, all individuals went on to 43 breed successfully the following season. In contrast, among older (20+ years) birds, 44 individuals that landed more often were more likely to defer breeding or fail during 45 incubation, suggesting they have lower foraging success. 46 5. As far as we are aware, this is the first demonstration of an age-specific carry-over effect 47 of foraging behaviour in the non-breeding period on subsequent reproductive 48 performance. This link between foraging behaviour and fitness in late but not early 49 3 adulthood indicates that the ability of individuals to forage efficiently outside the 50 breeding period may be an important driver of fitness differences in old age.