Extensive shell fishing and sewerage discharge in river estuaries could have serious consequences for the rare Icelandic black-tailed godwits that feed there. But it is the males that are more likely to suffer, according to new research from the University of East Anglia.
Research published today in the journal Ecology and Evolution reveals very different winter feeding habits between the sexes.
Both males and females mainly consume bivalve molluscs, sea snails and marine worms, probing vigorously into soft estuary mud with their long beaks. But the study shows that females, which are larger and have longer bills, are able to peck further into the silt to secure larger, deeper buried prey in areas that the shorter-billed males cannot reach. This means that human impacts on estuaries may have different impacts on males and females, depending on which prey sizes are most affected.
The godwit is a large, long-legged, long-billed migratory shorebird. It breeds almost exclusively in Iceland and winters on western European coasts, from the UK and Ireland in the north to the Iberian Peninsula in the south.
The 15-year study saw researchers weigh, measure, sex and ring-tag 1287 birds at locations including the Solent, the Wash Estuary in East Anglia, Iceland and Portugal. More than 2,000 volunteer observers took part in determining where males and females spend the winter, and the researchers measured what the birds were feeding on, how deeply they forage, and how quickly they find, catch and eat their prey.
Dr Jos Alves from UEA's school of Biological Sciences lead the research. He said: "We knew that females can be as much as 18 per cent larger than the males but we wanted to see what impact this difference had on their migration, feeding and segregation patterns.
"We found that the difference didn't have any impact on their distribution across the wintering area, as both sexes are able to cover th
|Contact: Lisa Horton|
University of East Anglia