Fig 1.
Estimated individual migratory routes.
Stopovers are marked as circles and their size represents duration (days) spent at them. Squares represent breeding sites in Europe and first wintering sites in Africa. Sites are shown with standard errors plotted as black asymmetrical crosses. APLORI, in central Nigeria, is marked with a cross. Continuous lines represent spring migration and dashed lines autumn migration. We used the most direct route when connecting locations, so these may not represent exact routes. Numbers in the upper left corners reflect individual ID.
Fig 2.
Migratory routes of Common Whitethroats wintering in Nigeria (A) and area utilised during the breeding season and at first wintering grounds (B).
Map A shows the migratory routes of Whitethroats wintering in Nigeria. The size of the circle represents the time spent at stopover sites. Lines represent the most direct route from one site to the next during spring (continuous line) and autumn (dashed line) migration. Squares represent breeding grounds (in Europe) and first wintering grounds (in Africa). Map B shows the area utilised during the breeding season and at first wintering grounds. Grey convex polygons represent the connection of outer locations. Lines connect breeding sites with respective first wintering sites and first wintering sites with APLORI (represented with a red cross). Note that because there was no data regarding the first wintering site of individual 094, this individual was excluded from both polygons and area estimates. Sites are shown with standard errors plotted as black asymmetrical crosses. Each colour is a different individual.
Fig 3.
Duration of spring migration (green square), breeding season (pink square) and autumn migration (orange square), and time spent at the first wintering site (blue square), and APLORI (yellow square; note that it ends on 31 December 2019 and does not reflect when individuals left the area). Annual latitudes (red line) and longitudes (blue line) of individuals. Hollow squares represent ± 14 days of equinoxes (green = spring [20 March], orange = autumn [23 September]). The black dotted line represents the day that the individual was first detected in APLORI.
Fig 4.
Common Whitethroats detected in both Europe and Africa.
Dots represent sites where individuals were ringed and/or recaptured and lines are the most direct route between them and do not reflect migratory routes. Map A) shows 31 individuals detected in Europe and Sub-Saharan Africa. Gray dots and lines are data collected from EURING (n = 25) and black dots and lines represent information collected in this study through geolocators (n = 6). Note that for the EURING data we cannot be certain whether sites in Sub-Saharan Africa represent final wintering locations or whether European sites are breeding sites. Map B) shows information from 96 individuals that were detected in Europe and North Africa collected through EURING. Colours represent the seasonal migration when individuals were detected in North Africa, red = autumn migration (August–December) and blue = spring migration (January–July).
Fig 5.
Days spent at stopovers located in different geographic locations during spring and autumn migration.
In spring, blue/bottom = pre-Sahara (stopovers before the Sahara Desert), yellow/middle = pre-Mediterranean (stopovers in North Africa) and green/top = Europe (stopovers in Europe before arriving at breeding grounds). In autumn, gray/top = Europe (stopovers in Europe after leaving breeding grounds), red/middle = pre-Mediterranean (stopovers in southern Europe, before crossing the Mediterranean Sea) and purple/bottom = post-Mediterranean (stopovers in North Africa). The direction of arrows represents the direction of migration.
Fig 6.
The number of stopovers in relation to spring and autumn departure dates.
The lines show the estimates for the effect of departure dates on number of stopovers, and gray areas reflect the 95% confidence intervals for the estimates.
Table 1.
Spring and autumn migration details.
Results from paired t-tests. All data from individual 094 was excluded. The time spent fattening at APLORI and breeding grounds during spring and autumn migration, respectively, are not considered in estimates.
Table 2.
Results from a generalised linear mixed model regarding total migration duration.
Formula: total migration duration from departure to arrival ~ start date + season + (1|individual).