Migration and wintering strategies in vulnerable Mediterranean Osprey populations

Abstract

A broad range of migration strategies exist in avian species, and different strategies can occur in different populations of the same species. For the breeding Osprey Pandion haliaetus populations of the Mediterranean, sporadic observations of ringed birds collected in the past suggested variations in migratory and wintering behaviour. We used GPS tracking data from 41 individuals from Corsica, the Balearic Islands and continental Italy to perform the first detailed analysis of the migratory and wintering strategies of these Osprey populations. Ospreys showed heterogeneous migratory behaviour, with 73% of the individuals migrating and the remaining 27% staying all year round at breeding sites. For migratory individuals, an extremely short duration of migration (5.2 AE 2.6 days) was recorded. Mediterranean Ospreys were able to perform long non-stop flights over the open sea, sometimes overnight. They also performed pre-and post-migratory trips to secondary sites, before or after crossing the sea during both autumn and spring migration. Ospreys spent the winter at temperate latitudes and showed high plasticity in habitat selection, using marine bays, coastal lagoons/marshland and inland freshwater sites along the coasts of different countries of the Mediterranean basin. Movements and home-range areas were restricted during the wintering season. The short duration of trips and high levels of variability in migratory routes and wintering grounds revealed high behavioural plasticity among individuals, probably promoted by the relatively low seasonal variability in ecological conditions throughout the year in the Mediterranean region, and weak competition for non-breeding sites. We stress the importance of considering the diversity in migration strategies and the particular ecology of these vulnerable populations, especially in relation to proactive management measures for the species at the scale of the Mediterranean region.

The recovery of Osprey populations in the Mediterranean basin

“…Monti et al . () concluded that this behavioural pattern was some kind of ‘selected’ migratory behaviour, typical of Mediterranean populations and completely different from the northern population of the species.…”

“…(, ), even if they have not been mentioned recently (Monti et al . ). Furthermore, no significant differences in DNA microsatellite markers among European populations were found, with only slight differences between Mediterranean island populations and north European populations, with a higher level of allele‐sharing among individuals in the former (Monti et al .…”

“…Consequently, Monti et al . () stressed the importance of carefully considering source populations for future translocations in the Mediterranean area, taking into account the particular migratory behaviour and ecology of these populations. In most of the reintroduction programmes, individuals from north and central Europe have been used as source populations for translocated young (Muriel et al .…”

“…Monti et al . () stated that Mediterranean island populations show different nest‐site selection, preferring marine cliffs and avoiding trees as substrate for nests. At the same time, these authors suggest some differences in preference for freshwater in northern populations as opposed to marine environments in the Mediterranean populations.…”

Testing alternative methods for estimation of bird migration phenology from GPS tracking data

“…The simplest one is the S method, in which birds reach or leave the breeding or wintering grounds after crossing Y latitude or boundary (López‐López et al , Hewson et al , Illan et al , King et al , Monti et al ). The AD method, which may incorporate a spatial threshold as well, sets the start of migration as the first day at which daily displacement (i.e.…”