Light‐level geolocators reveal migratory connectivity in European populations of pied flycatchers Ficedula hypoleuca

Abstract

Understanding what drives or prevents long-distance migrants to respond to environmental change requires basic knowledge about the wintering and breeding grounds, and the timing of movements between them. Both strong and weak migratory connectivity have been reported for Palearctic passerines wintering in Africa, but this remains unknown for most species. We investigated whether pied flycatchers Ficedula hypoleuca from different breeding populations also differ in wintering locations in west-Africa. Light-level geolocator data revealed that flycatchers from different breeding populations travelled to different wintering sites, despite similarity in routes during most of the autumn migration. We found support for strong migratory connectivity showing an unexpected pattern: individuals breeding in Fennoscandia (S-Finland and S-Norway) wintered further west compared to individuals breeding at more southern latitudes in the Netherlands and SW-United Kingdom. The same pattern was found in ring recovery data from sub-Saharan Africa of individuals with confirmed breeding origin. Furthermore, population-specific migratory connectivity was associated with geographical variation in breeding and migration phenology: birds from populations which breed and migrate earlier wintered further east than birds from 'late' populations. There was no indication that wintering locations were affected by geolocation deployment, as we found high repeatability and consistency in d 13 C and d 15 N stable isotope ratios of winter grown feathers of individuals with and without a geolocator. We discuss the potential ecological factors causing such an unexpected pattern of migratory connectivity. We hypothesise that population differences in wintering longitudes of pied flycatchers result from geographical variation in breeding phenology and the timing of fuelling for spring migration at the wintering grounds. Future research should aim at describing how temporal dynamics in food availability across the wintering range affects migration, wintering distribution and populations' capacity to respond to environmental changes.

Repeatability in Spring Arrival Dates in Pied Flycatchers Varies Among Years and Sexes

“…Pied Flycatchers are known to be faithful to their wintering sites (Salewski et al 2002), but this likely does not result in large within-population variation in migration distance. Recent geolocator data showed that our population is confined to a rather small wintering area (Ouwehand et al 2015). More generally, Pied Fly catchers winter in a rather narrow latitudinal band covering the Sudanian woodlands in West-Africa (Dowsett 2010), which results in small variation in potential migration distance, if we assume that all birds take roughly the same routes.…”

“…Assuming that longerwinged individuals fly faster than shorter-winged individuals, this could explain consistent variation in arrival time even if birds all depart at the same date. However, spring migration speed is already fast in Pied Flycatchers: Dutch, British and Finnish males with geolocators covered the distance between wintering and breeding grounds in c. 17 days, with little variation among individuals (Ouwehand et al 2015). Based on the low variation in migration duration, we consider it unlikely that the observed variation in arrival date that spans often more than two weeks between the first and last 10% of the distribution (Table 2) is entirely caused by variation in migration speed.…”

“…Timing of migration in this species is partly governed by photoperiods: in lab conditions, flycatchers only started spring migration when given photoperiodic cues of the normal wintering area (Gwinner 1996). Recent data from geolocators showed that males from our Dutch breeding population winter in eastern Guinea and western Ivory Coast (c. 5 -9°W), depart from the wintering grounds around the beginning of April and cover the 5000 km in about 18 days (Ouwehand et al 2015). Ring recoveries in northern Africa suggest that migration dates have advanced for our population, but we have yet no proof for an advance in spring arrival date (Hüppop & Winkel 2006, Both 2010.…”

Annual spatiotemporal migration schedules in three larger insectivorous birds: European nightjar, common swift and common cuckoo

“…Differences in fundamental niches alone are insufficient to explain, for instance, the striking differences, in some cases, between the wintering grounds and migration routes of closely related species, such as found in Ficedula flycatchers [8,9] and Luscinia nightingales [10,11]. Such patterns could be caused by different population histories (potentially explaining why birds circumvent the Mediterranean via the eastern or the western flyway) or competitive exclusion.…”

Insights into the migration of the European Roller from ring recoveries

“…Lightweight solar geolocators (Ouwehand et al 2015) and global positioning system tags (Hallworth and Marra 2015) now allow researchers to track the migration of all but the smallest of songbirds. However, these technologies are not without limitations .…”