Migratory Birds Leaving Earlier in Spring Because of Climate Change Still Arriving on Time
photo: Sébastien Bertu via flickr.
Some migrating birds may be more able to adapt to changing climate that previously thought. Writing in Current Biology researchers studying the migration patterns of pied flycatchers say that changing climatic conditions are indeed causing them to begin their migrations earlier in the spring, but it turns out that they are not actually arriving at their end destination earlier--something which would be devastating to them, as there would be less food for them on arrival:Weather in Southern Europe Halts Their Advance
Christian Both of University of Groningen:
We have been claiming for a while that migratory birds have difficulties in adapting to climate change because of their rigid and rather inflexible timing of spring migrations; in Africa and South America, they cannot know when spring starts at their northern breeding grounds.
This study shows that timing of spring migration is flexible and that birds do respond to climate change, although in a rather indirect way: breeding dates have become progressively earlier, and birds are thus born earlier in the spring. We now show that the effect of early birth is also that the birds migrate early, and migration time has advanced over the last 25 years. The reason that the birds did not advance their arrival is thus not due to a failure to start migration earlier, but because circumstances at passage in Southern Europe have not improved.
The pied flycatchers winter in West Africa, making a 5000-9000 kilometer migration to Europe and western Siberia every year. They pause along the route for a time in North Africa, to feed again for the remainder of the journey.
Both says that the birds were arriving in North Africa 10 days earlier in 2002 than they did in 1980, but aren't arriving in The Netherlands or in Sweden--a trip which takes six and twelve days, respectively--any earlier.
Will Species Be Able to Adapt Quickly Enough?
In terms of what this means for species ability to adapt to climate change, Both says, "Because climate change often alters temperatures differently at different periods in the year, adaptation of life cycles in animals with a complex annual cycle is not likely to be solved by simple phenotypic and evolutionary responses to earlier phenology...It remains to be seen whether evolution can alter species quickly enough to stop their decline."
Read the original journal article: Flexibility of Timing of Avian Migration to Climate Change Mashed by Environmental Constraints En Route
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