Migratory Herbivorous Waterfowl Track Satellite-Derived Green Wave Index

Abstract

Many migrating herbivores rely on plant biomass to fuel their life cycles and have adapted to following changes in plant quality through time. The green wave hypothesis predicts that herbivorous waterfowl will follow the wave of food availability and quality during their spring migration. However, testing this hypothesis is hampered by the large geographical range these birds cover. The satellite-derived normalized difference vegetation index (NDVI) time series is an ideal proxy indicator for the development of plant biomass and quality across a broad spatial area. A derived index, the green wave index (GWI), has been successfully used to link altitudinal and latitudinal migration of mammals to spatio-temporal variations in food quality and quantity. To date, this index has not been used to test the green wave hypothesis for individual avian herbivores. Here, we use the satellite-derived GWI to examine the green wave hypothesis with respect to GPS-tracked individual barnacle geese from three flyway populations (Russian n = 12, Svalbard n = 8, and Greenland n = 7). Data were collected over three years (2008–2010). Our results showed that the Russian and Svalbard barnacle geese followed the middle stage of the green wave (GWI 40–60%), while the Greenland geese followed an earlier stage (GWI 20–40%). Despite these differences among geese populations, the phase of vegetation greenness encountered by the GPS-tracked geese was close to the 50% GWI (i.e. the assumed date of peak nitrogen concentration), thereby implying that barnacle geese track high quality food during their spring migration. To our knowledge, this is the first time that the migration of individual avian herbivores has been successfully studied with respect to vegetation phenology using the satellite-derived GWI. Our results offer further support for the green wave hypothesis applying to long-distance migrants on a larger scale.

Forage plants of an Arctic‐nesting herbivore show larger warming response in breeding than wintering grounds, potentially disrupting migration phenology

“…This is a well‐known model system to study bird migratory timing in relation to the green wave (Shariatinajafabadi et al., 2014; van der Graaf et al., 2006) and climatic variables (Kölzsch et al., 2015). Our study sites are located in preferred feeding salt marsh habitats at three sites along this migratory flyway: one temperate wintering site, one temperate spring stopover site, and one Arctic breeding site (Figure 1).…”

“…A multitude of species match their period of reproduction to peaks in food availability in order to feed their young and to maximize their growth rates (Both & Visser, 2005). During spring migration, migratory species can also travel along a climatic gradient and match arrival on stopover sites to local peaks of food abundance along the gradient, described as the “green wave hypothesis” (Drent, Ebbinge, & Weijand, 1978; Shariatinajafabadi et al., 2014; Thorup et al., 2017; van der Graaf, Stahl, Klimkowska, Bakker, & Drent, 2006). This strategy is especially important for species which partly rely on capital body stores accumulated at staging sites for egg formation and incubation, such as geese (Drent et al., 2007; Gauthier, Bêty, & Hobson, 2003; Hahn, Loonen, & Klaassen, 2011).…”

“…As food peaks along the migratory flyway match the onset of spring (van der Graaf et al., 2006; van Eerden, Drent, Stahl, & Bakker, 2005), geese use these to time their migration (Duriez et al., 2009; Shariatinajafabadi et al., 2014; van Wijk et al., 2012). Food peak phenology might be differentially affected by climate warming at different latitudes, as plants in colder, higher latitudes might be more responsive to temperature increase (Havström, Callaghan, & Jonasson, 1993).…”

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“…The comparison of EVI data associated with collection sites 271 and randomly generated sites (Figure 4) confirms that the dynamic distribution of Painted 273 increased primary productivity across the landscape. Numerous studies have documented similar 274 associations including studies of Painted Buntings (Bridge et al, in press) and various tests of the 275 green-wave hypothesis (Drent et al, 1978;Owen, 1980, Shariatinajafabadi et al, 2014, Si et al, 276 2015. Therefore, we present this finding as validation that our specimen based distribution 277 mapping yields rather than a novel correlative observation.…”

Migration timing and stopover selection for barnacle geese Branta leucopsis

“…For each of the three years (2008)(2009)(2010), GPS tracks of incomplete spring migrations were removed from our analysis, resulting in 26 full data tracks for 12 female birds of the Russian population, 9 full data tracks for 8 male birds of the Svalbard population, and 7 full data tracks for 7 male birds of the Greenland population (see Table 2.1). The barnacle geese tracking data of all three populations can be viewed at movebank.org: Russian population: "Migration timing in barnacle geese (Barents Sea), data from Kölzsch et al and Shariatinajafabadi et al 2014 Kölzsch et al and Shariatinajafabadi et al 2014", DOI: 10.5441/001/1.5d3f0664. …”