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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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Food and social cues modulate reproductive development but not migratory behavior in a nomadic songbird, the Pine Siskin
Abstract Many animals rely on photoperiodic and non-photoperiodic environmental cues to gather information and appropriately time life-history stages across the annual cycle, such as reproduction, molt, and migration. Here, we experimentally demonstrate that the reproductive physiology, but not migratory behavior, of captive Pine Siskins (Spinus pinus) responds to both food and social cues during the spring migratory-breeding period. Pine Siskins are a nomadic finch with a highly flexible breeding schedule and, in the spring, free-living Pine Siskins can wander large geographic areas and opportunistically breed. To understand the importance of non-photoperiodic cues to the migratory-breeding transition, we maintained individually housed birds on either a standard or enriched diet in the presence of group-housed heterospecifics or conspecifics experiencing either the standard or enriched diet type. We measured body condition and reproductive development of all Pine Siskins and, among individually housed Pine Siskins, quantified nocturnal migratory restlessness. In group-housed birds, the enriched diet caused increases in body condition and, among females, promoted reproductive development. Among individually housed birds, female reproductive development differed between treatment groups, whereas male reproductive development did not. Specifically, individually housed females showed greater reproductive development when presented with conspecifics compared to heterospecifics. The highest rate of female reproductive development, however, was observed among individually housed females provided the enriched diet and maintained with group-housed conspecifics on an enriched diet. Changes in nocturnal migratory restlessness did not vary by treatment group or sex. By manipulating both the physical and social environment, this study demonstrates how multiple environmental cues can affect the timing of transitions between life-history stages with differential responses between sexes and between migratory and reproductive systems.
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- PAR ID:
- 10498602
- Publisher / Repository:
- Oxford University Press
- Date Published:
- Journal Name:
- Ornithology
- Volume:
- 141
- Issue:
- 2
- ISSN:
- 0004-8038
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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