Either taking it easy or feeling too tired: old Cory’s Shearwaters display reduced activity levels while at sea

Abstract

It has long been known that birds change their behaviour, reproductive performance and survival as they mature, including in the first few years after recruitment into the breeding population. However, and contrasting with the description of patterns of actuarial and reproductive senescence in later years, there are surprisingly few studies documenting changes in behaviour in old individuals. Such studies are important, as birds provide particularly interesting models for studying the biology of senescence. It has been suggested that, unlike mammals, birds may remain physically fit until an advanced age, yet this has limited empirical support. In this paper, we used activity (immersion) loggers to show that old ([26 years) Cory's Shearwaters Calonectris diomedea are less active when foraging at sea, spend more time resting on the water and have a smaller number of take-offs and landings during darkness, when compared to experienced mid-aged individuals (13-20 years old). Old individuals also tended to have reduced immune response against an experimental challenge using phytohaemagglutinin. These results are in line with observed reductions in activity levels with age in a wide range of non-avian taxa, and may suggest that old seabirds are physically less fit than younger individuals. Alternatively, old birds might simply be more experienced and their reduction in activity might reflect a strategic regulation of investment in different activities. Our study illustrates the potential for gaining insights into avian aging patterns and processes by looking into the behaviour of model organisms. We therefore encourage more research focusing on behavioural parameters that may reflect variations in physical condition or strategic choices, during both the breeding and non-breeding seasons.

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

“…Old animals are expected to suffer from deterioration in muscular or physiological condition (Nussey et al., ), which is reflected in reduced foraging activity or ability (Catry et al., ; MacNulty et al., ). However, reduced activity may not necessarily indicate a decrease in foraging success (i.e., foraging senescence), if animals are able to increase their efficiency with age (Catry et al., ; Weimerskirch, Gault, & Cherel, ). As expected, older birds were less active; however, in contrast to our prediction that less active individuals would have a lower probability of breeding successfully, reduced foraging activity was linked to higher fitness.…”

“…We also determined whether there was age‐related variation in breeding metrics within our sample of tracked birds, and linked age‐related changes in foraging behaviour to subsequent reproductive performance. We predicted that old birds would (1) have reduced activity, and forage further south than younger birds, based on the results of previous studies during breeding (Table ; Catry et al., ; Catry, Granadeiro, Ramos, Phillips, & Oliveira, ; Lecomte et al., ). We also predicted that (2) older birds would have a lower probability of breeding successfully in the following season (Froy et al., ), and (3) that age‐related trends in foraging behaviour would be linked to lower subsequent breeding success in older birds.…”

Age, sex, and breeding status shape a complex foraging pattern in an extremely long‐lived seabird

“…Seabirds, together with flamingos and parrots, reach the longest maximum life spans among birds, with some petrels and albatrosses living .30 years (Wasser and Sherman 2010). Compared to mid-aged seabirds, the few existing studies suggest that old breeders feed on different proportions of prey (Navarro et al 2010), perform longer foraging trips with reduced activity and lower mass gain (Catry et al 2006(Catry et al , 2011, and dive longer with the same prey pursuit rate (Zimmer et al 2011). Compared to mid-aged seabirds, the few existing studies suggest that old breeders feed on different proportions of prey (Navarro et al 2010), perform longer foraging trips with reduced activity and lower mass gain (Catry et al 2006(Catry et al , 2011, and dive longer with the same prey pursuit rate (Zimmer et al 2011).…”

Sexual display complexity varies non-linearly with age and predicts breeding status in greater flamingos

“…Alternatively, old birds might be more experienced at successfully acquiring a reproductive partner, and a lower SDC could simply correspond to a modulation of their investment in sexual display42. However, this explanation is unlikely as the probability to become a breeder increased with increasing SDC for both males and females.…”