Table 1.
Summary data for the 28 Vega gulls included in this study.
Fig 1.
Individual tracks (black lines) and seasonal Kernel Utilisation Distribution (KUD; smoothing factor: 100 km) maps based on the movements of 28 Vega gulls.
Blue squares show trapping sites. The four panels present the four seasons of the Vega gull annual cycle (a winter, b spring, c summer, d autumn), with spring and autumn defined as the periods when birds migrate (see S1 Fig (DC = 2) and [35]). The map used as the background was downloaded from http://thematicmapping.org/downloads/world_borders.php and has a Creative Commons Attribution license CC BY-SA 3.0.
Fig 2.
Seasonal changes in the latitudinal distribution of Vega gulls spending summer (A) within (above 64.9°N) or (B) outside (below 60°N) their known breeding range (the fixes of one bird were split between the two panels; see Methods). The black line shows the mean latitude of all birds for each day of the year while the grey lines show the maximum and minimum latitudes recorded during these days for single birds.
Fig 3.
Annual phenology of 21 Vega gulls summering within the breeding range between 2015 and 2019.
Lines represent the extend of breeding (black), migratory (light grey), and wintering (dark grey) periods (exact dates are given in S2 Table).
Fig 4.
Days of active migration in spring (blue) and autumn (ochre) for 13 Vega gulls.
Boxes hold 50% of the values, with the median shown as a horizontal line and the mean as an ‘x’. Whiskers extend to the highest and lowest values excluding outliers.
Fig 5.
Duration of individual migratory windows of 13 Vega gulls during spring and autumn migrations (A), and proportion of days of active migration during population (B) and individual (C) migratory window. Boxes hold 50% of the values, with the median shown as a horizontal line and the mean as an ‘x’. Whiskers extend to the highest and lowest values excluding outliers.
Fig 6.
Daily distances (left) and proportion of the migration route travelled during days of active migration (right) by 13 Vega gulls in spring (blue) and autumn (ochre). Boxes hold 50% of the values, with the median shown as a horizontal line and the mean as an ‘x’. Whiskers extend to the highest and lowest values excluding outliers.
Fig 7.
Diel patterns of 15 Vega gulls monitored in 2h bouts.
Proportion of bouts is given for daylight (blue), twilight (ochre) and night (grey). Panel (A) presents the pattern for migration bouts only and must be compared with panel (B; all bouts) to infer which periods of the day are preferred for migration. The total number of recorded bouts is given in the bars.
Fig 8.
Median rates of travel (in km/h with 95% CI) of 15 Vega gulls during the day (blue), twilight (ochre) and night (grey): (A) migration bouts, (B) other bouts. Boxes hold 50% of the values, with the median shown as a horizontal line. Whiskers extend to the highest and lowest values excluding outliers.
Fig 9.
Median (dots) and maximum (lines) altitudes (in meters above sea level) of 15 Vega gulls during the day (blue), twilight (ochre) and night (grey): (A) Migration bouts, (B) Other bouts. Only medians estimated with 20 or more bouts are shown.
Fig 10.
Within- and between-individual variation in movements in four seasons, as measured by Dynamic Time Warping (DTW).
Boxes hold 50% of the values, with the median shown as a horizontal line. Whiskers extend to the outer 95% of the values. Sample sizes are given above the boxplots.