The final stage of migration, when animals terminate migratory movements and transition to a more sedentary state, remains the least understood phase of migration. Whereas migrants that return to the same locations each year may use mechanisms associated with locating a specific destination, migrants with low site fidelity, such as nomadic migrants, may rely on local environmental cues to determine when to cease migratory movements. Using an experiment with captive birds, we tested whether the presence of a conspecific influences the termination of migration, indicated by changes in behaviour and physiology, in a nomadic migrant (the pine siskin, Spinus pinus ). We paired migratory birds with a non-migratory individual or left migratory and non-migratory individuals unpaired. Migratory paired birds had a significant decline in nocturnal activity immediately after pairing and activity levels remained lower two weeks later, with significant declines in energetic reserves and flight muscle size also observed. By contrast, migratory unpaired birds maintained high levels of activity and energetic reserves. These results provide evidence for a role of the social environment in migratory termination decisions. Social cues may be particularly useful in nomadic migrants, such as pine siskins, to facilitate settling in high quality, but unfamiliar, habitats.
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Telomere length predicts timing and intensity of migratory behaviour in a nomadic songbird
Our understanding of state-dependent behaviour is reliant on identifying physiological indicators of condition. Telomeres are of growing interest for understanding behaviour as they capture differences in biological state and residual lifespan. To understand the significance of variable telomere lengths for behaviour and test two hypotheses describing the relationship between telomeres and behaviour (i.e. the causation and the selective adoption hypotheses), we assessed if telomere lengths are longitudinally repeatable traits related to spring migratory behaviour in captive pine siskins ( Spinus pinus ). Pine siskins are nomadic songbirds that exhibit highly flexible, facultative migrations, including a period of spring nomadism. Captive individuals exhibit extensive variation in spring migratory restlessness and are an excellent system for mechanistic studies of migratory behaviour. Telomere lengths were found to be significantly repeatable ( R = 0.51) over four months, and shorter pre-migratory telomeres were associated with earlier and more intense expression of spring nocturnal migratory restlessness. Telomere dynamics did not vary with migratory behaviour. Our results describe the relationship between telomere length and migratory behaviour and provide support for the selective adoption hypothesis. More broadly, we provide a novel perspective on the significance of variable telomere lengths for animal behaviour and the timing of annual more »
- Award ID(s):
- 1755245
- Publication Date:
- NSF-PAR ID:
- 10353891
- Journal Name:
- Biology Letters
- Volume:
- 18
- Issue:
- 8
- ISSN:
- 1744-957X
- Sponsoring Org:
- National Science Foundation
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