by Anna Alquitela
Greenland white-fronted geese, Anser albifrons flavirostris, spend their winters in Ireland, stage and refuel in Iceland, and breed in Greenland. Because climate change has advanced the spring thaw in Ireland by about 18 days since 1985, these geese have more food to eat and are departing for and arriving in Iceland earlier than previous years. However, climate change has not caused a significant change in the temperatures of Icelandic staging areas and therefore has not caused a significant change in the departure time from Iceland to Greenland, thus the geese are staying in Iceland for a longer period of time than in previous years and arriving at their breeding grounds around the same time as historically known. Fox et al. (2014) used an abdominal profile index (API) as an indicator of fat stores in geese to determine if the amount of stored fat was the cause of advanced departure to Iceland. The authors also considered trends in temperature as indicators of departure time, but found that, because of the migration distances from Ireland to Iceland and Iceland to Greenland, temperatures are “very poor predictors” for departure times; meaning that the geese would not be able to use the temperature in Ireland to predict the temperature in Iceland nor the temperature in Iceland to predict the temperature in Greenland. Compared to previous studies, Fox et al. found that the Greenland white-fronted geese departed Ireland 33 days earlier in 2012 than they did in 1969 and arrived in Iceland 22 days earlier in 2012 than they did in 1997. The authors also note that the mean API at departure from Ireland in 2012 and 2013 increased significantly from previous years.
The study by Fox et al. has determined that, though temperature is not a determinant of migratory dates, climate change has affected spring thaw which allows for earlier grass growth, in turn leading to advanced fat storage in Greenland white-fronted geese and causing them to depart from their wintering grounds earlier than in previous years. The staging area in Iceland is at an agricultural university farm where there is more than enough available food for the geese. This is likely the reason why the geese are not migrating from Iceland to Greenland sooner. Because temperatures in Greenland have not affected snow levels there, it is important that the geese arrive in ideal health in order to reproduce optimally.
Fox, A. D., Weegman, M., Bearhop, S., Hilton, G., Griffin, L., Stroud, D. A., & Walsh, A. 2014. Climate change and contrasting plasticity in timing of a two-step migration episode of an Arctic-nesting avian herbivore. Current Zoology, 60, 233-242.
TAGS: Anthony D Fox, Mitch D Weegman, Stuart Bearhop, Geoff M Hilton, Larry Griffin, David A Stroud, Alyn Walsh, Anser albifrons flavirostris, Greenland white-fronted geese, migration phenology, climate mismatch, vernal migration