Hernández, N., Oro, D and Sanz-Aguilar, A., Environmental conditions, age and senescence differentially influence survival and reproduction in the Storm Petrel. 2017. Journal of Ornithology. Volume 158, pp 113–123. DOI:
10.1007/s10336-016-1367-x
Abstract: Demographic parameters in wild populations are expected to be shaped by
individual covariates and environmental variability. Thus, the
understanding of the effects of age and/or environmental conditions on
variability in vital rates is of special importance in ecological and
evolutionary studies. Early age-related improvements in survival and
reproduction and later declines due to senescence are expected, above
all in long-lived species. Survival in these species is predicted to be a
more conservative parameter than reproduction, thereby giving rise to
less temporal variability. We studied age-dependent patterns of survival
and breeding success in a long-lived seabird, the Mediterranean Storm
Petrel Hydrobates pelagicus melitensis,
and the additive influence of individual heterogeneity and
environmental climatic variables using 22 years of individual-based data
(1993–2014). The North Atlantic Oscillation index (NAO) and sea surface
temperature (SST) were selected as proxies of environmental conditions
in both breeding and wintering areas. Our results show that vital rates
improved with age for both survival and breeding success. A slow effect
of senescence at older ages was detected for breeding success, whereas
models did not disentangle the occurrence or the absence of actuarial
senescence. Reproduction was also influenced by the age of first
observed reproduction: at the same age, more experienced birds that
recruited earlier had a higher breeding success than less experienced
ones. Breeding success (but not survival) also showed great temporal
variability in accordance with theoretical predictions. Neither the NAO
nor the SST explained this variability, probably because petrels feed on
lower trophic levels than most pelagic seabirds and other physical
features such as river runoffs and winds may be involved, as well as
other environmental stressors such as predation by sympatric gulls.
viernes, 27 de enero de 2017
miércoles, 11 de enero de 2017
New publication on Egyptian vulture demographic parameters!
Sanz-Aguilar, A., Cortés-Avizanda, A., Serrano, D., Blanco, G., Ceballos, O., Grande, J.M., Tella, J.L., Donázar, J.A.: Sex- and age-dependent patterns of survival and breeding success in a long-lived endangered avian scavenger. Scientific Report, 7 2017 Article number 40204, doi: 10.1038/srep40204
Abstract. In long-lived species, the age-, stage- and/or sex-dependent patterns of survival and reproduction determine the evolution of life history strategies, the shape of the reproductive value, and ultimately population dynamics. We evaluate the combined effects of age and sex in recruitment, breeder survival and breeding success of the globally endangered Egyptian vulture (Neophron percnopterus), using 31-years of exhaustive data on marked individuals in Spain.
Photo: J. Bas |
Mean age of first reproduction was 7-yrs for both sexes, but females showed an earlier median and a larger variance than males. We found an age-related improvement in breeding success at the population level responding to the selective appearance and disappearance of phenotypes of different quality but unrelated to within-individual aging effects. Old males (≥8 yrs) showed a higher survival than both young males (≤7 yrs) and females, these later in turn not showing aging effects. Evolutionary trade-offs between age of recruitment and fitness (probably related to costs of territory acquisition and defense) as well as human-related mortality may explain these findings. Sex- and age-related differences in foraging strategies and susceptibility to toxics could be behind the relatively low survival of females and young males, adding a new concern for the conservation of this endangered species.
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