Data from: Reproductive trade-offs in a long-lived bird species: condition-dependent reproductive allocation maintains female survival and offspring quality

Life-history theory is an essential framework to understand the evolution
of reproductive allocation. It predicts that individuals of long-lived
species favour their own survival over current reproduction, leading
individuals to refrain from reproducing under harsh conditions. Here we
test this prediction in a long-lived bird species, the Siberian jay
Perisoreus infaustus. Long-term data revealed that females rarely refrain
from breeding, but lay smaller clutches in unfavourable years. Neither
offspring body size, female survival nor offspring survival until the next
year was influenced by annual condition, habitat quality, clutch size,
female age, or female phenotype. Given that many nests failed due to nest
predation, the variance in the number of fledglings was higher than the
variance in the number of eggs and female survival. An experimental
challenge with a novel pathogen before egg-laying largely replicated these
patterns in two consecutive years with contrasting conditions. Challenged
females refrained from breeding only in the unfavourable year, but no
downstream effects were found in either year. Taken together, these
findings demonstrate that condition-dependent reproductive allocation may
serve to maintain female survival and offspring quality, supporting
patterns found in long-lived mammals. We discuss avenues to develop
life-history theory concerning strategies to offset reproductive costs.