title: Forecasting spring from afar? Timing of migration and predictability of phenology along different migration routes of an avian herbivore.
abstract: Herbivorous birds are hypothesized to migrate in spring along a seasonal gradient of plant profitability towards their breeding grounds (green wave hypothesis). For Arctic breeding species in particular, following highly profitable food is important, so that they can replenish resources along the way and arrive in optimal body condition to start breeding early. We compared the timing of migratory movements of Arctic breeding geese on different flyways to examine whether flyways differed in the predictability of spring conditions at stopovers and whether this was reflected in the degree to which birds were following the green wave. Barnacle geese (Branta leucopsis) were tracked with solar GPS/ARGOS PTTs from their wintering grounds to breeding sites in Greenland (N = 7), Svalbard (N = 21) and the Barents Sea (N = 12). The numerous stopover sites of all birds were combined into a set of 16 general stopover regions. The predictability of climatic conditions along the flyways was calculated as the correlation and slope between onsets of spring at consecutive stopovers. These values differed between sites, mainly because of the presence or absence of ecological barriers. Goose arrival at stopovers was more closely tied to the local onset of spring when predictability was higher and when geese attempted breeding that year. All birds arrived at early stopovers after the onset of spring and arrived at the breeding grounds before the onset of spring, thus overtaking the green wave. This is in accordance with patterns expected for capital breeders: first, they must come into condition; at intermediate stopovers, arrival with the food quality peak is important to stay in condition, and at the breeding grounds, early arrival is favoured so that hatching of young can coincide with the peak of food quality. Our results suggest that a chain of correlations between climatic conditions at subsequent stopovers enables geese to closely track the green wave. However, the birds' precision of migratory timing seems uninfluenced by ecological barriers, indicating partly fixed migration schedules. These might become non-optimal due to climate warming and preclude accurate timing of long-distance migrants in the future.
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.|Project Group Movement Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.|Department of Migration and Immuno-Ecology, Max Planck Institute for Ornithology, 78315, Radolfzell, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Kölzsch
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.|Department of Bird Migration, Swiss Ornithological Institute, 6204, Sempach, Switzerland.
authors.forename: Silke
authors.initials: S
authors.lastname: Bauer
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.
authors.forename: Rob
authors.initials: R
authors.lastname: de Boer
authors.affiliation: WWT Caerlaverock Wetland Centre Eastpark Farm, Dumfries DG1 4RJ, UK.
authors.forename: Larry
authors.initials: L
authors.lastname: Griffin
authors.affiliation: Environmental Consultancy Services, Carrigskeewaun, Carrowniskey, Westport, Co. Mayo, Ireland.
authors.forename: David
authors.initials: D
authors.lastname: Cabot
authors.affiliation: Institute of Avian Research "Vogelwarte Helgoland", 26386, Wilhelmshaven, Germany.
authors.forename: Klaus-Michael
authors.initials: KM
authors.lastname: Exo
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.|Vogeltrekstation - Dutch Centre for Avian Migration and Demography (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.
authors.forename: Henk P
authors.initials: HP
authors.lastname: van der Jeugd
authors.affiliation: Department of Animal Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.|Project Group Movement Ecology, Netherlands Institute of Ecology (NIOO-KNAW), 6708 PB, Wageningen, The Netherlands.
authors.forename: Bart A
authors.initials: BA
authors.lastname: Nolet
mesh_terms: D025041:Animal Migration; D000818:Animals; D001110:Arctic Regions; D005060:Europe; D005260:Female; D020387:Food Chain; D005777:Geese / Q000502:physiology*; D008297:Male; D012621:Seasons
keywords: Branta leucopsis; GDD jerk; barnacle goose; capital breeding; climatic barrier; green wave hypothesis; migration flyway; onset of spring