(CN) – Rising Arctic temperatures force barnacle geese to rush north along their migration routes, but speeding up their trip is not helping their reproduction according to research published Thursday.
The barnacle geese shorten travel time from wintering grounds in Ireland, Scotland and England by making fewer stops as they fly up to 1,900 miles to their annual Arctic breeding grounds on the coasts of Greenland, Norway and Russia. While earlier spring warmth triggers the need to migrate more quickly, it does not speed up egg laying once the geese are on their breeding grounds, scientists with the Netherlands Institute of Ecology and University of Amsterdam say.
Fewer stops on route mean birds arrive without the calories needed to assist their bodies in egg production. This delays egg-laying, and ultimately goslings hatch after their food sources have peaked – leading to lower survival rates.
The geese feed on grasses and coastal plants found in salt marshes, grasslands near river estuaries or tidal mud flats. The new study shows that fewer hatchlings survive long enough to leave their mothers’ sides and make the trek back to wintering spots on their own. As a result of the post-migration recovery period, chicks continue to hatch too late to take advantage of early spring foraging opportunities.
Researchers say their findings suggest the birds will be in trouble unless they start heading north for the Arctic earlier in the year, rather than speeding up their travel along the way. Barnacle geese most likely rely heavily on cues like day length that aren’t changing with the temperature rise, according to Bart Nolet, co-author of the study.
“The birds are leaping in the dark as they cannot predict, while being at the wintering grounds in temperate areas, whether it is going to be an early or late spring in the Arctic,” Nolet said. “The weather systems in the temperate and Arctic regions are not linked, and on top of that, temperature rise is far stronger in the Arctic than in the temperate region.
“Only halfway through the migration, the geese are probably able to judge from environmental cues what spring will be like up in the Arctic, and they are apparently able to speed up if spring is early.”
Whether these migrants can adapt their cue sensitivity and match their migration timing to a changing climate remains uncertain. But there are signs that the geese may be flexible enough to adjust by other means. In fact, Nolet said some barnacle geese have recently given up migration, breeding instead in the temperate region.
“Geese migrate in families, and young learn the route and timing from their parents,” Nolet said. “On the one hand, this leads to traditional patterns; on the other hand, it can lead to rapid adjustments when some birds experience that doing the migration differently – often induced by extreme weather events – pays off.”
The researchers combined remote sensing, bird tracking, stable isotope techniques and field observations along the birds’ entire flyway to explore the effect of climate warming on migration and breeding times of barnacle geese.
Through comparisons of the migratory and non-migratory geese, the team hopes to learn more about the costs and benefits of migration.
Their research is published in Current Biology.
The Netherlands Organization for Scientific Research and a Marie Curie Intra-European Fellowship provided research funding.