Egg shuffle reveals how innate drivers and early environments affect European songbird’s ranges

Migratory birds fly precise seasonal paths to their breeding and non-breeding grounds, even when those grounds are separated by thousands of miles. But how do the birds know the difference between these two areas – is this information innate, or is it learned as hatchlings? The answers may affect how or if these birds can adapt to potential shifts in these grounds caused by global climate change. To learn more about what determines the non-breeding ranges of the pied flycatcher, Koosje Lamers and colleagues performed an egg shuffle, moving eggs from nests in the Netherlands to Sweden in a five-year experiment. The resulting “common garden” of fully genetic Dutch birds hatched in Dutch nests, genetically Dutch but Swedish-hatched birds, and fully genetic and hatched Swedish birds offered a way to track differences in migratory journeys. The researchers found that both inheritance and the hatching environment determined non-breeding areas, with the “half Dutch” birds traveling to non-breeding areas that were intermediate in location between the fully Swedish and Dutch populations.