The hypothalamic–pituitary–adrenal (HPA) axis coordinates an organism's response to environmental stress. The responsiveness and sensitivity of an offspring's stress response may be shaped not only by stressors encountered in their early post‐natal environment but also by stressors in their parent's environment. Yet, few studies have considered how stressors encountered in both of these early life environments may function tog...

An individual's telomere length early in life may reflect or contribute to key life‐history processes sensitive to environmental variation. Yet, the relative importance of genetic and environmental factors in shaping early‐life telomere length is not well understood as it requires samples collected from multiple generations with known developmental histories. We used a confirmed pedigree and conducted an animal model analysis...

We investigated the link between heterozygosity and the reaction norm attributes of reproductive performance in female house sparrows ( Passer domesticus ). We collected data on clutch size, egg size, hatching success and nestling survival in 2816 nesting attempts made by 791 marked individuals over a 16‐year period. Pedigree analysis revealed no evidence of inbreeding. Neither parent–offspring regression nor an animal model r...

Recent studies of extra‐pair paternity have found support for the idea that heterozygous males have an advantage in siring offspring. Most studies use DNA microsatellite loci to determine paternity and then use the same loci to estimate individual heterozygosity. However, because the likelihood of detecting extra‐pair offspring depends on the combinations of parental alleles, it is possible that biases arise from particular al...

Phenotypic plasticity is a widespread phenomenon and may have important influences on evolutionary processes. Multidimensional plasticity, in which multiple environmental variables affect a phenotype, is especially interesting if there are interactions among these variables. We used a long‐term data set from House Sparrows ( Passer domesticus ), a multi‐brooded passerine bird, to test several predictions from life‐history theo...

Extra‐pair paternity (EPP) is a widespread and highly variable reproductive phenomenon in birds. We tested the effects of habitat, spatial factors, and timing of breeding on the occurrence of EPP in red‐winged blackbirds ( Agelaius phoeniceus ). We used PCR‐amplified microsatellites to assess the paternity of 1479 nestlings from 537 broods on 235 territories over four breeding seasons. Over 4 years, 40% of nestlings were extra...