Figure 1.
Spring migration route for three barnacle goose populations from their wintering to their breeding sites.
The yellow, green and red arrows indicate the Russian, Svalbard and Greenland flyways, respectively. In each flyway, the dots show examples of the spatial distribution of GPS locations recorded for the 12 Russian, 8 Svalbard and 7 Greenland barnacle geese, from 2008 to 2010.
Table 1.
Tag ID, year of tracking, and number of stopover sites for each barnacle goose.
Figure 2.
The GWI summary plots showing plant phenology over three years (2008–2010).
The Russian (A), Svalbard (B) and Greenland (C) flyways are indicated. The GWI is estimated from MODIS NDVI and ranges from 0% (minimum greenness) to 100% (maximum greenness). The northward spring migration has been shown on the GWI background, as well as the return movement throughout the year. Each dot in the figure represents the average of both the latitude of the site locations and the time for 12 Russian, 8 Svalbard and 7 Greenland barnacle geese, from 2008 to 2010. The site locations include breeding (black dots), overwintering (blue dots), and stopover (red dots) sites for the spring migration and white dots for the autumn migration. The map of each flyway with the site locations overlaid is shown in the right-hand column. The white smoothed line shows the general migration pattern of the geese with respect to the vegetation phenology. The black bands on the western flyways (Svalbard and Greenland) indicate areas with no NDVI information (i.e. ocean).
Figure 3.
The northward movement of three individual barnacle geese in relation to the green wave.
The map indicates the Russian (A), Svalbard (B), and Greenland flyways (C). The individuals’ IDs were: 78045, 178199, and 78207 for birds on the Russian, Svalbard and Greenland flyways, respectively, in 2008.
Figure 4.
The relationship between date of 50% GWI and arrival date at stopover sites during migration.
The Russian (A), Svalbard (B) and Greenland (C) barnacle goose populations are indicated. The solid black line shows the OLS regression line, while the dotted line is the 1∶1 line. The red line shows the 95% confidence interval. GWI = green wave index, DOY = day of the year counting from 1st January.
Table 2.
Results of ordinary least squares regression between the arrival date of the barnacle geese at the stopover sites and the date of 50% GWI, for three different flyways, from 2008 to 2010.
Figure 5.
Box plots showing the development of the green wave index (GWI) at stopover sites.
The range of GWI values is shown for the three flyways (A), and for the three different years (2008–2010) (B). Each box plot shows the median (line within the box), the 25th percentile (lower end of the box), the 75th percentile (upper end of the box), and 10th to 90th percentile (solid lines). The open circles show the outliers. The significant differences in GWI at the stopover sites between the three different flyways and the three different years seen in an ANOVA analysis using a Bonferroni correction are indicated (here p-value = 0.05/3). ***p≤0.001, ns = non-significant.
Table 3.
Summary statistics of a factorial ANOVA examining the effects of flyway, year and their interaction on GWI values at stopover sites.