Do Arctic breeding geese track or overtake a green wave during spring migration?

Abstract

Geese breeding in the Arctic have to do so in a short time-window while having sufficient body reserves. Hence, arrival time and body condition upon arrival largely influence breeding success. The green wave hypothesis posits that geese track a successively delayed spring flush of plant development on the way to their breeding sites. The green wave has been interpreted as representing either the onset of spring or the peak in nutrient biomass. However, geese tend to adopt a partial capital breeding strategy and might overtake the green wave to accomplish a timely arrival on the breeding site. To test the green wave hypothesis, we link the satellite-derived onset of spring and peak in nutrient biomass with the stopover schedule of individual Barnacle Geese. We find that geese track neither the onset of spring nor the peak in nutrient biomass. Rather, they arrive at the southernmost stopover site around the peak in nutrient biomass, and gradually overtake the green wave to match their arrival at the breeding site with the local onset of spring, thereby ensuring gosling benefit from the peak in nutrient biomass. Our approach for estimating plant development stages is critical in testing the migration strategies of migratory herbivores.

Resource tracking within and across continents in long-distance bird migrants

“…Studies of diverse marine organisms have linked distributions and movements of diverse marine organisms to sea surface temperature and net primary productivity (NPP) ( 1 , 2 ), whereas elephants track precipitation-driven vegetation dynamics ( 3 ) and other ungulates wander to optimize the nutritional content of the grasses they eat ( 4 , 5 ). Migrating birds also track vegetation dynamics, the so-called green wave surfing; that is, the birds move northward, timed with the seasonally progressing green-up of vegetation ( 6 – 8 ). …”

“…However, the hypothesized link between movements and seasonal regional resources throughout the annual cycle has never been properly established, and the precise timing of annual individual schedules relative to seasonally induced local dynamics in habitats, food resources, and climate remains restricted to parts of the annual cycle in long-distance migrants ( 6 – 8 , 13 , 15 , 16 , 25 ). In order to establish potential links between resources and annual bird movements, we have combined the results of high–temporal resolution tracking of individual birds with monitoring variation in local ecological conditions across the seasonally changing globe.…”

Large herbivores surf waves of green-up during spring

“…The forage maturation hypothesis has helped frame studies of foraging by large herbivores for over a quarter of a century. As high-resolution spatial data and analyses are allowing more rigorous tests of the GWH [3,7], it is becoming increasingly important to more fully integrate these two hypotheses. In a sense, the GWH, when applied to large herbivores, is the spatial manifestation of the forage maturation hypothesis.…”

Assessing migration patterns inPasserina cirisusing the world’s bird collections as an aggregated resource

“…This bias is not surprising given as we might expect collectors to work in productive areas that feature an abundance of birds, but it points to a shortcoming of most specimen-derived datasets—i.e., a lack of systematic or truly random sampling. Nevertheless, numerous studies have documented similar associations between migration routes and primary productivity, including studies of Painted Buntings (Bridge et al, 2015) and various tests of the green-wave hypothesis (Drent, Ebbinge & Weijand, 1978; Owen, 1980; Shariatinajafabadi et al, 2014; Si et al, 2015). Therefore, we present this finding as validation that our specimen based distribution mapping confirms expected patterns, rather than a novel correlative observation.…”