Extreme migration and the individual quality spectrum
Costs of migration, in terms of time, energy, and mortality risk, have a strong theoretical and empirical foundation in the study of birds. We expect these costs to be most severe for extreme long-distance migratory landbirds, whose demanding annual routines (e.g. non-stop flights > 8000 km and r...
| Published in: | Journal of Avian Biology |
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| Main Authors: | , , , |
| Format: | Article in Journal/Newspaper |
| Language: | English |
| Published: |
2017
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| Subjects: | |
| Online Access: | https://hdl.handle.net/11370/dbd23870-6c33-445e-9e93-5af12b97b0e7 https://research.rug.nl/en/publications/dbd23870-6c33-445e-9e93-5af12b97b0e7 https://doi.org/10.1111/jav.01316 https://pure.rug.nl/ws/files/40567846/JAvianBiol2017_extreme_migration_and_the_individual_quality_spectrum_Conklin_et_al.pdf |
| Summary: | Costs of migration, in terms of time, energy, and mortality risk, have a strong theoretical and empirical foundation in the study of birds. We expect these costs to be most severe for extreme long-distance migratory landbirds, whose demanding annual routines (e.g. non-stop flights > 8000 km and return journeys > 30 000 km) may approach their maximum physiological capabilities. To explore whether this is true, we review evidence in long-jump migratory shorebirds (Scolopacidae), focusing most on the prototypical example, the Alaska-breeding bar-tailed godwit Limosa lapponica baueri. Contrary to expectations, these and similar birds demonstrate high adult survival, little evidence for elevated mortality during migration, no apparent minimisation of non-stop flight distances, and low inter- and intra-individual variation in migration performance. Two key aspects of extreme migrants may explain these findings: 1) a counter-intuitively conservative annual-cycle strategy, which minimises risks and enables dissipation of carry-over effects before fitness consequences arise; and 2) selection pressure during early life, which quickly removes low-performing individuals from the population. We hypothesise that these two factors, applicable to extreme strategies in a wide range of taxa, act to truncate the range of individual quality in a population, and decrease the prevalence and detectability of carry-over effects. Testing these hypotheses is challenging, as it requires comparative studies of demography and individual quality spectra along a continuum of extremeness. However, it has important potential implications for interpreting individual variation, designing studies of cross-seasonal interactions or costs of migration, and recognising early-warning signs of population decline. For example, the most extreme shorebird migrations rely on abundant but difficult-to-access resources; the high minimum individual performance required for survival predicts that degradation of these resource hot-spots will propel rapid ... |
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