Restringido

On their route to tropical Africa, European trans-Saharan migrants must cross two major geographical barriers, the Mediterranean Sea and the Sahara Desert, which necessitates
the accumulation of large fuel loads. While northern Africa is the chief region where most migrants gain fuel for the Sahara crossing, Iberia is a target area to gain fuel before the sea
crossing existing between Europe and Africa. Despite the large body of studies approaching the question of fuel accumulation before geographic barriers, it is still poorly known which factors apart from distance to a certain barrier shape the geographical pattern of fuel reserves. To investigate this question in detail we used data of first-year Reed WarOrnis Fennica 91:00–00. 2014
blers from 12 localities within Iberia during the autumn migration period of 2009. We run linear models to analyze the effects of location in Iberia, date, and body size on body mass variation at each migratory flyway (eastern, central and western Iberia). Flight ranges from each site were also calculated. Our results showed that Reed Warblers in Iberia had the necessary fuel needed to arrive in northern Africa but not to tropical Africa. However, body mass patterns varied depending on the geographical region (eastern, central or western Iberia). Date did not affect body mass in central and western Iberia, but in eastern Iberia heavier birds tended to pass later. Thus, the factors shaping body mass of Reed Warblers in Iberia before the sea crossing to Africa seemed to be more complex than just the
distance to this geographical barrier, with underlying stopover quality-associated factors possibly playing a relevant role.

Andueza,M., Barba, E., Arroyo, J.L., Feliu, J., Gómez, J., Jubete, F., Lozano, L., Monrós, J.S., Moreno-Opo, R., Neto, J.M., Onrubia, A., Tenreiro, P., Valkenburg, T., Arizaga, J., 2014. Geographic variation in body mass of first-year ReedWarblers Acrocephalus scirpaceus in Iberia. Ornis Fennica 91, 88-99.