Disentangling Migratory Routes and Wintering Grounds of Iberian Near-Threatened European Rollers Coracias garrulus

Abstract

Long-distance migrants are suffering drastic declines in the last decades. Causes beneath this problem are complex due to the wide spatial and temporal scale involved. We aim to reveal migratory routes, stopover areas, wintering grounds, and migratory strategies for the most southwestern populations of the near-threatened European Roller Coracias garrulus in order to identify conservation key areas for the non-breeding stage of this species. To this end, we used tracking data from seven satellite transmitters fitted to birds breeding in different populations throughout the Iberian Peninsula and four geolocators fitted to individuals in a southeastern Iberian population. Precise satellite data were used to describe daily activity patterns and speed in relation to the main regions crossed during the migration. Individuals from the most southwestern Iberian populations made a detour towards the Atlantic African coast whereas those from northeastern populations followed a straight north-to-south route. We identified important stopover areas in the Sahel belt, mainly in the surroundings of the Lake Chad, and wintering grounds on southwestern Africa farther west than previously reported for the species. Concerning the migratory strategy, satellite data revealed: 1) a mainly nocturnal flying activity, 2) that migration speed depended on the type of crossed habitat, with higher average speed while crossing the desert; and 3) that the migration was slower and lasted longer in autumn than in spring. The studied populations showed weak migratory connectivity, suggesting the confluence of birds from a wide range of breeding grounds in a restricted wintering area. Therefore, we suggest to target on defining precisely key areas for this species and identifying specific threats in them in order to develop an appropriate global conservation programme for the European Roller.

A pan‐European, multipopulation assessment of migratory connectivity in a near‐threatened migrant bird

“…Given that the roller is predominantly a sit‐and‐wait predator (so unlikely to ‘fly‐and‐forage’) and an active, flapping flier, we expected migration to be punctuated by stopovers for refuelling (Alerstam & Hedenström, ), the locations of which are clearly important from a conservation perspective. Our study supports previous work identifying the northern savanna zone, particularly the Lake Chad basin, as an important autumn stopover site for rollers from western European populations (Catry et al ., ; Emmenegger et al ., ; Rodríguez‐Ruiz et al ., ). We also show that individuals from eastern populations make use of this area.…”

“…We randomly selected one ‘high‐quality’ (up to 1.5 km accuracy) location per day and defined stopover and winter periods (mean ± SD position) as all points reflecting <20 km movement in a 24‐h period (see Rodríguez‐Ruiz et al . () for full details).…”

Actogram analysis of free-flying migratory birds: new perspectives based on acceleration logging

“…The results indicate that this species maintain its nocturnal migration habits when crossing the desert (Rodríguez-Ruiz et al 2014). Perhaps this is also what the large numbers of nocturnal passerine migrants do.…”

Insights into the migration of the European Roller from ring recoveries

“…We present the first Europe-wide analysis of Roller ring recovery data, complementing several recent tracking studies (Emmenegger et al 2014;Catry et al 2014;Finch et al 2015;Rodríguez-Ruiz et al 2015). We gathered 57 records of Rollers recovered on migration and one winter record.…”