Individual variation in orientation promotes a 3000‐km latitudinal change in wintering grounds in a long‐distance migratory raptor

Abstract

Migrating juvenile birds rely on endogenous information in choosing the direction in which to fly, but such input may be overridden by social interactions with experienced individuals. We tagged seven juvenile Short‐toed Eagles Circaetus gallicus with GPS transmitters in southern Italy. This trans‐Saharan migrant flies mainly by soaring and is therefore not well adapted to performing long water crossings. Five of the seven tagged juveniles used the longer but apparently safer route towards the Strait of Gibraltar, and two migrated along a southerly trajectory and subsequently spent the winter in Sicily, apparently forced to do so by the 150‐km‐wide Sicily Channel. One of these individuals took the longer route the following autumn. These results, combined with long‐term (15 years) visual field observations involving thousands of individuals, suggest that inexperienced Short‐toed Eagles may learn their migratory routes from experienced adults, whereas some of them migrate south in response to an innate orientation instinct. Transport costs, inherited information and geography apparently interact, forcing some Short‐toed Eagles to winter 3000 km to the north of the majority of their conspecifics.

Wind conditions and geography shape the first outbound migration of juvenile honey buzzards and their distribution across sub-Saharan Africa

“…Moreover, the honey buzzards were not as reluctant to engage in long sea-crossings as many larger soaring migrants [21,23]. Nevertheless, and contrary to our expectations, geography affected the longitude at which certain individuals settled.…”

Sea crossing as a major determinant for the evolution of migratory strategies in soaring birds

“…Adapted from Duriez et al. (2018), Mellone, Lucia, Mallìa, and Urios (2016) and Panuccio et al. (2014)…”

Rectification of Abnormal Migration Recorded in Hand-reared Red-crowned Cranes (Grus japonensis)

“…Artificial interventions are encouraged in protecting endangered species with small population size (Wang et al 2018). Inexperienced migrants of some bird taxa (e.g., passerines and raptors) may rely on inherent navigation system to find correct way to wintering area for their first migration (Berthold 2004;Thorup et al 2007;Mellone et al 2016). For birds migrating in flocks (e.g., storks, cranes and bustards), the importance of learning has been proved: inexperienced migrants follow their parents or other elder group members for their first migration, so that correct migration route can be passed on (Palacín et al 2011).…”