Migratory herbivorous waterfowl track satellite-derived green wave index

PLoS One. 2014 Sep 23;9(9):e108331. doi: 10.1371/journal.pone.0108331. eCollection 2014.

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.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Altitude
  • Analysis of Variance
  • Animal Migration*
  • Animals
  • Biomass
  • Food Supply
  • Geese / physiology*
  • Greenland
  • Herbivory / physiology*
  • Least-Squares Analysis
  • Models, Biological
  • Plants*
  • Russia
  • Seasons
  • Spacecraft*
  • Svalbard

Grant support

This research received financial support from the EU Erasmus Mundus External Cooperation Window (EM8) Action 2 project, http://www.erasmusmundus8.net/ (project number 10438223). Tracking devices for the Greenland barnacle geese were provided by Dr. David Cabot (5) and the WWT (2). Tracking devices for the Svalbard barnacle geese were provided through grants from Scottish Natural Heritage, Solway Coast Area of Outstanding Natural Beauty Sustainable Development Fund, the BBC, and the Heritage Lottery Fund Awards for All. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.