Longevity and lifetime reproductive success of barn swallow offspring are predicted by their hatching date and phenotypic quality

Abstract

Summary1. Longevity is a major determinant of individual differences in Darwinian fitness. Several studies have analyzed the stochastic, time-dependent causes of variation in longevity, but little information exists from free-ranging animal populations on the effects that environmental conditions and phenotype early in ontogeny have on duration of life. 2. In this long-term (1993-2011) study of a migratory, colonial, passerine bird, the barn swallow (Hirundo rustica), we analyzed longevity and, in a subsample of individuals, lifetime reproductive success (LRS) of the offspring that reached sexual maturity in relation to hatching date, which can affect the rearing environment through a seasonal deterioration in ecological conditions. Moreover, we analyzed the consequences of variation in body size and, for the first time in any species, of a major component of immunity on longevity, both by looking at absolute phenotypic values and at deviations from the brood mean. 3. Accelerated failure time models showed that individuals of both sexes that hatched early in any breeding season enjoyed larger longevity and larger LRS, indicating directional selection for early breeding. Both male and female offspring with large T cell-mediated immune response relative to their siblings and female nestlings that dominated the brood size ⁄ age hierarchy had larger longevity than their siblings of inferior phenotypic quality ⁄ age. Conversely, absolute phenotypic values did not predict longevity. 4. Frailty modelling disclosed marked spatial heterogeneity in longevity among colonies of origin, again stressing the impact of rearing conditions on longevity. 5. This study therefore reinforces the notion that perinatal environment and maternal decisions over timing and site of breeding, and position in the brood hierarchy can have marked effects on progeny life history that extend well into adulthood. In addition, it provides the first evidence from any bird population in the wild that immune response when nestlings predicts individuals' longevity after sexual maturation.

Nestling telomere length does not predict longevity, but covaries with adult body size in wild barn swallows

“…Hence, the present study does not support the idea that TL predicts longevity. Since longevity is a major determinant of lifetime reproductive success [17], our study provides no evidence for selection on TL, at least in males, for which we had a large sample. However, it should also be considered that telomere restriction fragment analysis by Southern blot or real-time PCR might have masked the relationship between TL and longevity [19], although that was not the case in other studies [6,15].…”

“…Because hatching failure and nestling mortality rates in barn swallows are low [17], it seems unlikely that the lack of a sex difference resulted from TL-related differential mortality before blood sampling in either sex, with males and females differing in TL at the zygote stage.…”

“…In addition, we captured the vast majority of the breeding individuals every year. Thus, individuals that were not captured in the colony where they bred in the previous year could be considered dead [17], allowing us to measure longevity. We used accelerated failure time (AFT) and Cox regression models to investigate variation in longevity in relation to TL (see also [17] for coding of longevity).…”

“…We marked nestlings and sampled blood between day 10 and 13 post-hatching over the 1997-2008 breeding seasons. Less than 5% of the offspring were recruited locally as 1-year-old breeders [17]. Keel length (reflecting body size), and wing and tail length were measured in the year of recruitment.…”

Observational field studies reveal wild birds responding to early-life stresses with resilience, plasticity, and intergenerational effects

“…By contrast, late-fledged male and female wild Barn Swallows (Hirundo rustica) showed shorter longevity and diminished lifetime reproductive success (Saino et al 2012), and female Pied Flycatchers (Ficedula hypoleuca) that fledged in poor condition laid smaller eggs (Potti 1999), although effects on fitness were not measured.…”