Increased juvenile survival may not be universally linked to longevity : ecological, social and life-history drivers of age-specific mortality in birds

A classical prediction of the traditional evolutionary theories of ageing (tETA) is that longevity should be positively correlated with survival early on in life. However, large and unexplained variation exists in juvenile survival-longevity combinations. Here, we provide the first comparative study investigating the life-history, ecological and social correlates of juvenile survival, longevity and their combinations in 204 bird species. Overall, both measurements were positively correlated, but multiple survivals’ combinations evolved, some in accordance with tETA ("positive JS-L combinations") while others contrasting it ("JS-L mismatches"). Positive JS-L combinations covaried with the pace of life proxies, whereas mismatching combinations covaried with the growing season length, where long growing seasons promoted juvenile survival, while short growing seasons promoted longevity. Interestingly, sociality explained only positive combinations, while life-history and ecological traits explained both positive and mismatching combinations. Overall, these findings challenge a main prediction of the tETA, and identify key evolutionary forces driving the coevolution between juvenile survival and longevity

Family living: an overlooked but pivotal social system to understand the evolution of cooperative breeding

Bird breeding systems are more diverse than previously appreciated. Here we show that defining an intermediate breeding system, family breeding, where individuals postpone their dispersal but do not cooperate in reproduction, is a natural extension of the widely accepted 2-category system (pair vs. cooperative breeding). Evolution of prolonged association of offspring with parents appears to be possible in cases where it extends into unfavorable periods of environmental conditions such as autumn/winte

data of each analysis from the article

This file has three sheets. One for each analysis mentioned in the article. Each sheet contains the raw response variable (in bold) fixed and random effects

Prey selection by the common dolphin: fulfilling high energy requirements with high quality food

International audienceWhich characteristics define the prey species constituting the diet of a given predator? Answering this question would help predict a predator's diet and improve our understanding of how an ecosystem functions. The aim of this study was to test if the diet of common dolphins, Delphinus delphis, in the oceanic Bay of Biscay reflected prey availability or a selection shaped by prey energy densities (ED). To do this, the community of potential prey species, described both in terms of relative abundance and energy densities, was compared to the common dolphin diet in this area. This analysis of a predator's diet and its prey field revealed that the common dolphin selected its diet on the basis of prey energy densities (significant values of Chesson's index for ED>5kJ.g-1). High-energy prey were positively selected in the diet [e.g. Notoscopelus kroeyeri, ED=7.9 kJ.g-1, 9% of relative abundance in the environment (%Ne); 62% of relative abundance in the diet (%Nd)] and low-energy prey disregarded (Xenodermichthys copei, ED=2.1kJ.g-1, 20%Ne, 0%Nd). These results supported the hypothesis that common dolphins selected high energy density prey species to meet their energetically expensive life style and disregard prey organisms of poor energy content even when abundant in the environment

Data from: Experience buffers extrinsic mortality in a group-living bird species

Extrinsic mortality has a strong impact on the evolution of life-histories, prey morphology and behavioural adaptations, but for many animals the causes of mortality are poorly understood. Predation is an important driver of extrinsic mortality and mobile animals form groups in response to increased predation risk. Furthermore, in many species juveniles suffer higher mortality than older individuals, which may reflect a lower phenotypic quality, lower competitiveness, or a lack of antipredator or foraging skills. Here we assessed the causes of mortality for 372 radio tagged Siberian jays. This sedentary bird species lives in family groups that contain a breeding pair as well as related and unrelated non-breeders. Ninety-five percent of death were due to predation (N=59 out of 62 individuals) and most individuals were killed by Accipiter hawks. Multivariate Cox proportional hazards models showed that non-breeders had a lower survival than breeders, but only in territories in managed forest with little visual cover. Examining breeders, only sex influenced survival with males having a lower survival than females. For non-breeders, juveniles had lower survival than older non-breeders, and those on managed territories had lower survival than those on unmanaged territories. Additionally, a low feather quality reduced the survival probability of non-breeders only. Thus, living on managed territories and having a low feature quality only affected non-breeders, particularly juveniles. These findings add to previous research demonstrating that juvenile Siberian jays acquire critical antipredator skills from experienced group members. Thus, experience can buffer extrinsic mortality, highlighting that group living not only provides safety in numbers, but also provide social opportunities to learn critical life-skills

predator encounter data

data used in predator encounter analysi

survival data

data used for survival analyses in pape

Experience buffers extrinsic mortality in a group-living bird species

Extrinsic mortality has a strong impact on the evolution of life-histories, prey morphology and behavioural adaptations, but for many animals the causes of mortality are poorly understood. Predation is an important driver of extrinsic mortality and mobile animals form groups in response to increased predation risk. Furthermore, in many species juveniles suffer higher mortality than older individuals, which may reflect a lower phenotypic quality, lower competitiveness, or a lack of antipredator or foraging skills. Here we assessed the causes of mortality for 371 radio tagged Siberian jays. This sedentary bird species lives in family groups that contain a breeding pair as well as related and unrelated non-breeders. Ninety-five percent of death were due to predation (n = 59 out of 62 individuals) and most individuals were killed by Accipiter hawks. Multivariate Cox proportional hazards models showed that non-breeders had a lower survival than breeders, but only in territories in managed forest with little visual cover. Examining breeders, only sex influenced survival with males having a lower survival than females. For non-breeders, juveniles had lower survival than older non-breeders, and those on managed territories had lower survival than those on unmanaged territories. Additionally, a low feather quality reduced the survival probability of non-breeders only. Thus, living on managed territories and having a low feature quality affected only non-breeders, particularly juveniles. These findings add to previous research demonstrating that juvenile Siberian jays acquire critical antipredator skills from experienced group members. Thus, experience can buffer extrinsic mortality, highlighting that group living not only provides safety in numbers, but also provide social opportunities to learn critical life-skills