Effects of parental age at conception on offspring life history trajectories in a long-lived bird

Parental age at conception can have both short- and long-term consequences on the health, survival, and reproduction of their offspring. To date, most of our knowledge comes from laboratory studies, and considers the effects of maternal age and a "snapshot" of the life history trajectory of the offspring. Here, we use a multigenerational demographic dataset in a free-living, long-lived (median lifespan is 7 years old) bird, the Alpine swift (Tachymarptis melba), to investigate the effects of maternal and paternal age on offspring traits, from nestling to adulthood, and considering all major life history traits, from growth and age at first reproduction to reproductive success and lifespan. Parental age affected offspring phenotype before fledging and lifespan, but differently so for sons and daughters. Offspring from old-age mothers (≥11 years old) and fathers (≥9 years old) were bigger and less infested by ectoparasites before fledging, except sons from old-age fathers that show no reduction in ectoparasite load. We also report evidence of negative effects of paternal age on the lifespan of their offspring (i.e., Lansing effect), with sons (but not daughters) from old-age fathers having shorter lifespans. Our findings highlight the importance of the transgenerational effects of parental age at conception on the reproductive performance, survival, and phenotype of their offspring.