Younger birds are migrating earlier because of changes to nesting and hatching patterns. Dr. Jenny Gill, from the UEA's school of Biological Sciences, said, “We have known that birds are migrating earlier each year, particularly those that migrate over shorter distances.”
The research team looked at a population of Icelandic Black-tailed Godwits over 20 years. During this time period, the flock advanced their spring arrival date by two weeks. However, tracking individual birds shows a different migration pattern. Individual birds do almost exactly the same thing every year, i.e. arriving punctually at the same time.
"Climate change is likely to be driving this modification because black tailed godwits nest earlier in warmer years, and birds that hatch earlier will have more time to gain the body condition needed for migration and to find good places to spend the winter, which can help them to return early to Iceland when they come back to breed, added Gill."
Bird migration is complex, and difficult to generalize. Even within closely related species the pathways and strategies may differ. Birds use varying migratory strategies depending on mode of flight, migration distance, and the species’ natural history. Migration timings are therefore not common among species migrating over long distances because many long-distance migrants arrive so late on the breeding grounds that they have little opportunity to respond to warming conditions by nesting earlier.
The study done is extremely crucial because many long-distance migrant bird populations are currently declining very rapidly, and identifying how climate change is affecting the population is a key part of understanding the cause of the decline.
The research team has been supported by a network of more than 2,000 birdwatchers who reported sightings of colour-ringed Black-tailed Godwits as they travelled from Iceland to Spain and Portugal. The research was funded by Natural Environmental Research Council.
Photo by newsonair.