Long‐distance migrants face numerous challenges during their migration, with the spring migration timing being particularly important, as early arrival at the breeding grounds often enhances breeding success. Both innate and environmental factors influence migration timing in birds, and the earlier arrival of males than females is common among songbirds breeding in temperate zones. The great reed warbler Acrocephalus arundinaceus males departed from the wintering grounds 10.5 days earlier than females. Interestingly, the oldest males (≥ 4‐year‐olds) departed significantly earlier than younger adult males (2‐ and 3‐year‐olds), suggesting that accumulated experience and/or age‐related hormonal changes may underlie this pattern. No significant differences were observed among female age groups. In contrast, we found no significant age effect for the duration of spring migration in either males or females. Males arrived 9.9 days earlier than females at the breeding grounds. Similar to departure dates, the oldest males (≥ 4‐year‐olds) arrived significantly earlier than middle‐aged males (3‐year‐olds), while no such age‐dependent relationship was observed in females. In both males and females, we found positive relationships between the departure date from the wintering grounds and the arrival date at the breeding grounds with a slope of β = 0.59, showing that spring migration duration becomes shorter as the spring season progresses. In addition, for a given departure date from the wintering grounds, males arrived 3.9 days earlier than females, but no significant differences were observed between age groups either in males or females. Our findings have important implications for understanding how long‐distance migratory birds might adjust their endogenous migration programs based on individual qualities, and highlight the potential role of learning and experience in these processes. This further emphasizes how adaptations to ongoing climate change might depend not only on individual quality, but also on plasticity and the age structure of the population.
Malmiga et al. (Sun,) studied this question.