Riddle of Early Bird Migration Cracked
In the northern hemisphere, birds now return from their winter migrations sooner. Yet, ornithologists don’t know exactly how the birds adapted to return earlier. One possible explanation holds that individual birds changed their behavior to return sooner.
However, recent research observed that individual birds haven’t changed their schedules. Instead, the results of a 14-year-long study of a migratory shore bird species suggested that early-born birds get more worms and can migrate sooner.
In the study, an international network of more than 2,000 volunteer birdwatchers recorded sightings of Icelandic black-winged godwits (Limosa limosa islandica) migrating from Portugal and Spain to Iceland between 1999 and 2004. The citizen scientists observed that individual birds returned on nearly the same date each year. As these birds returned each year to find an earlier greening of Iceland, the monogamous mated pairs of godwits could nest and hatch eggs sooner. The new generation of birds matured and began their migration cycle earlier.
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