Exploring intraspecific variation in migratory destinations to investigate the drivers of migration

Abstract

Various benefits (e.g. tracking of resources and of climate niche) and costs (e.g. distance travelled) are hypothesized to drive seasonal animal migrations. Until now, these potential factors have been investigated together at the species level, but migratory movements are made at the individual level, leading to intraspecific variability. Here, we use ringing/recovery data from 1308 individuals belonging to thirteen North American bird species to analyse patterns in intraspecific variability of migratory destinations in order to investigate which factors underpin bird migration and how individuals trade‐off among multiple factors. Our results suggest that migratory destinations have been shaped by access to resources (most important during the breeding season) and climatic niche tracking (during winter, mostly). However, the benefits of resource surpluses and climate niche tracking appear to be traded off against the cost of migratory distance, which seems to strongly constrain where individuals migrate.

Scaling migrations to communities: An empirical case of migration network in the Arctic

“…The proportion of migratory species is strongly correlated with the magnitude of seasonality, at least for terrestrial bird communities (Hurlbert and Haskell, 2003;Somveille et al, 2013). Also, migratory birds tend to relocate from breeding to non-breeding grounds by minimizing migration distance to reach suitable grounds in terms of climate and resources, akin to a refuge from the harsher conditions of the breeding ground (Somveille et al, 2015(Somveille et al, , 2019(Somveille et al, , 2021Bonnet-Lebrun et al, 2021). Unsurprisingly, most migratory species from Bylot Island reach non-breeding grounds in temperate environments (intermediate migration distance from the focal community), suggesting an influence of community geographical location on the structure of migratory pathways.…”

“…Replicating our approach with several communities and comparing their metrics may reveal global biogeographic patterns of migratory pathways at the community level. Migratory pathways of avian species tend to converge towards the poles and migratory species tend to minimize migration distance (Somveille et al, 2015(Somveille et al, , 2019(Somveille et al, , 2021Bonnet-Lebrun et al, 2021), so the structure of community migration networks could possibly vary with latitude. Quantifying the flow of migratory organisms in community migration networks would allow for a better representation of connections at the meta-level, providing a more direct way to link migrations to ecosystem and community processes.…”

Context drives movement patterns in a mobile marine predator

“…Large magnitudes of seasonal temperature changes also impose direct physiological constraints: Pacific bluefin tuna ( Thunnus thynnus ), for example, seasonally leave productive feeding areas, migrating to warmer latitudes, in order to remain within thermal optima [ 59 ]. This demonstrates the importance of maximizing time spent within suitable temperatures over increased food availability, which is also a common trade-off for migratory bird species when tracking resources [ 60 ].…”

Eco‐evolutionary drivers of avian migratory connectivity

“…Hence, our model was also re-fitted to explicitly account for this benefit by replacing nonbreeding latitude with the annual resource surplus available to geographical populations, quantified according to Somveille et al (2019). The normalized difference vegetation index (NDVI) was used as a general proxy of resource availability (Bonnet-Lebrun et al, 2021;Somveille et al, 2019). For both seasonal ranges, we calculated the difference between the mean NDVI when the population is present and the mean NDVI when the population is absent, and took their sum as a proxy of the annual resource surplus, a relative measure of the net gain in resource availability due to migration (Appendix S8, for details).…”