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Linking range wide energetic trade-offs to breeding performance in a long-distance migrant


Carneiro, Camilo et al. (2021), Linking range wide energetic trade-offs to breeding performance in a long-distance migrant, Dryad, Dataset,


Understanding how individual trade-offs and carry-over effects along the annual cycle influence fitness is fundamental to unravel population dynamics, but such data is particularly challenging to collect in long-distance migrants. Here, with a full annual cycle perspective of Icelandic whimbrels Numenius phaeopus islandicus, we investigate trade-offs across the entire distribution, assessing migration costs and wintering energetic balance experienced throughout the wintering range (from temperate to tropical regions), and link these to breeding parameters for two wintering regions. We found that Icelandic whimbrels traded-off higher costs of migration with more favourable wintering conditions, in terms of energetic balance. By migrating further, whimbrels experience lower thermoregulatory costs and higher net energetic intake rates, resulting in a more positive energetic balance during winter. However, these differences did not appear to carry-over into the breeding season in terms of measurable effects on laying date (and, consequently, fledging success) or egg volume, suggesting that individual fitness is unlikely to be significantly influenced by previous wintering conditions, although effects on other traits may potentially occur. Nevertheless, Icelandic whimbrels seem to favour wintering locations where the conditions are more advantageous, as the abundance of individuals at the wintering sites reflects the variation in site quality.