Save horseshoe crabs to save the red knot argues scientist

By Colin Ricketts - 06 Jul 2011 20:19:0 GMT
Save horseshoe crabs to save the red knot argues scientist

A symbiotic relationship could be the key to the future of the red knot, the small at-risk bird which feeds on horseshoe crabs on the American east coast during its annual migration.

The U.S. Geological Survey led study is published in Ecosphere, a journal of the Ecological Society of America and finds that the numbers of red knots, which have plummeted in the last 15 tears, are dependent on this important food source.

"This is one of the first studies to scientifically support the ecological links between these two species," said Conor McGowan, a USGS scientist and the lead author of the study.

The horseshoe crab is used by fisherman as bait to catch other sea creatures and its blood is used by drug companies which prize its clotting ability.

The 12-year study looked at more than 16,000 of the little birds, and found that the Delaware Bay is a vital feeding station during their migration. Weight gain, which is important to survival of the long-distance-travelling species, is directly related to numbers of spawning crabs.

"Our research strongly suggests that the timing of horseshoe crab spawning, not simply crab abundance, is important to red knot refuelling during their stops in Delaware Bay," McGowan said.

Water temperatures are one of the triggers to spawning, along with tides, lunar cycles and storms. Climate change is raising temperatures and there has also been an increase in extreme weather conditions helping to throw the two species' calendars out of sync.

"If the timing of migration and the availability of food resources - in this case, horseshoe crab eggs - do not coincide, migrating shorebirds, such as the red knot, that come to Delaware Bay each spring, could be adversely affected, both individually and as a population," McGowan said.

To make matters worse, the birds are also threatened by snow conditions in the Arctic where they breed.

"We were surprised to find that snow depth in the arctic breeding grounds increases the chances of survival for both heavy and light birds," said McGowan.

McGowan is advocating further research in the Arctic and for controls on horseshoe crab harvests.

Top Image Credit: © Guido Akster