Sex-specific migration strategies and underlying physiology contribute to spring arrival protandry in a songbird

• Published in: Behavioral ecology and sociobiology 2024-08, Vol.78 (7), p.85, Article 85
• Main Authors: Bojarinova, Julia, Demina, Irina, Chetverikova, Raisa, Babushkina, Olga, Tsvey, Arseny
• Format: Article
• Language: English
• Subjects: Animal Ecology; Autumn; Bats; Behavioral Sciences; Biomedical and Life Sciences; Bird migration; Breeding grounds; Breeding sites; Circadian rhythms; Diurnal; Emberiza schoeniclus; Females; Flight; Foraging behavior; Gender differences; Life Sciences; Locomotor activity; Males; Migration; Migratory birds; Migratory species; Nocturnal; Original Article; Overwintering behavior; Physiology; Protandry; Seasonal variations; Sex differences; Sexual behavior; Songbirds; Spring; Spring (season); Zoology
• ISSN: 0340-5443; 1432-0762
• DOI: 10.1007/s00265-024-03499-8

In spring, many migrating songbirds exhibit protandry (the phenomenon whereby males precede females in arrival at breeding sites). The reed bunting ( Emberiza schoeniclus ) is a short-distance European migrant which expresses a high degree of protandry and combines both nocturnal and diurnal movements during migrations. In experimental conditions, we studied the proximate mechanisms of protandry and compared locomotor behavior between spring and autumn migrations. We assumed that captive behavior is a proxy for the behavior that birds demonstrate in the wild. Combined, the analysis of seasonal patterns and circadian dynamics of locomotor activity suggested that male reed buntings depart from wintering grounds by daytime flights approximately two weeks earlier than females. Later, they develop nocturnal activity, take off shortly before dawn and continue their flight for several hours in the morning. We argue that such behavior allows males to benefit from both the advantage of nocturnal flight and an efficient start of foraging, thereby reducing the stopover duration (by minimizing search/settling costs) and increasing the total migration speed. In contrast, females express predominantly nocturnal migratory activity in spring. We observed that in spring males had lower fat reserves compared to females. We suggest that males can forage during diurnal movements and therefore do not need to store large energetic reserves. In contrast, in autumn, both sexes display similar patterns of locomotor activity and fat reserves. Overall, our results describe unique sex-specific migratory behaviour and physiology in reed buntings in spring, which, we assume, contribute to spring arrival protandry in this species. Significance statement To reach their destinations, migratory bird species adopt specific strategies reflected in behavior and/or physiology. In many species, males arrive earlier to the breeding grounds (a phenomenon called protandry). Knowledge of migratory strategies in species that experience both nocturnal and diurnal flights is scarce. To study the mechanisms that lead to protandry in nocturnal/diurnal migrant, we kept reed buntings ( Emberiza schoeniclus ) under experimental conditions that mimicked changes in photoperiod experienced by free-living birds from autumn migration through wintering to spring migration and recorded the dynamics of their locomotor activity and fat reserves. In spring, we observed sex differences in the seasonal patterns and ci