Insights into the migration of the European Roller from ring recoveries

Here we present the first international analysis of ring recovery data in the European Roller - a long distance migrant of conservation concern - comprising 58 records of Rollers ringed during the breeding season and recovered during the non-breeding season. Most records come from eastern Europe, half are of juveniles and over three quarters are of dead birds. Thus, ring recoveries provide migration data for cohorts of Rollers - juveniles and unsuccessful migrants - for which no information currently exists, complementing recent tracking studies. Qualitatively, our results are consistent with direct tracking studies, illustrating a broad-front migration across the Mediterranean basin in autumn and the use of the Arabian Peninsula by Rollers from eastern populations in spring. Autumn movements were, on average, in a more southerly direction for juveniles than adults, which were more easterly. After the exclusion of outliers, juvenile movements were also more variable. This is consistent with juveniles following a naïve vector-based orientation program, and perhaps explains the 'moderate' migratory connectivity previously described for the Roller. The recovery age ratio was juvenile-biased in autumn but adult-biased in spring. Although this difference was not significant, it points towards a higher non-breeding season mortality of juveniles than adults. We also provide the first (qualitative) analysis of causes of non-breeding season mortality, highlighting the high prevalence of shooting.