Climate change could leave the rufa red knot hungry

Climate change may extensively reduce the red knot’s Arctic breeding habitat and the roosting habitats the knot uses as it migrates south along the eastern U.S. Credit: Greg Breese/USFWS

You just finished a workout and are ready for a nice meal to replenish your energy. However, every restaurant you go to is closed. A couple of restaurants take pity on you and offer table scraps, but it’s not enough nourishment for your tired body.

A changing climate is causing a similar problem for the rufa red knot, which we recently determined needs protection as a threatened species. This shorebird flies thousands of miles every spring from the coasts of southern Chile and Argentina, or from wintering areas in the Gulf of Mexico, to breed in the Arctic. Every fall it reverses its migration and heads south. Some knots fly almost 19,000 miles every year.

Red knot infographic

In the spring, many knots stop in Delaware Bay. They have learned the exact time to stop so they can replenish their energy and prepare for the final leg of the journey north. That time also is when horseshoe crabs lay their eggs – which the birds chow down on and, in the process, double their body weight.

Red knots nearly double their weight eating these horseshoe crab eggs at Delaware Bay in the spring. Mispillion Harbor, Delaware. Credit: Gregory Breese/USFWS

Red knots nearly double their weight eating these horseshoe crab eggs at Delaware Bay in the spring. Mispillion Harbor, Delaware. Credit: Gregory Breese/USFWS

At least they normally do.

Several factors may keep rufa red knots from accessing a bounty of crab eggs. Sometimes, horseshoe crabs lay their eggs later than normal due to storms, which are projected to become more intense and irregular as the climate warms. But coastal waters are also warming, which will likely lead to crabs laying their eggs earlier than normal, before most knots have arrived. Whichever the case, the knot arrives too early or too late for the harvest, and it can be left with “table scraps.”

Red knots flying over Mispillion Harbor, Delaware. Credit: Gregory Breese/USFWS

Red knots at Mispillion Harbor, Delaware. Delaware Bay hosts the largest concentration of the rufa red knot subspecies during the spring, when knots on their marathon migrations stop to refuel and take advantage of the largest gathering of horseshoe crabs in the world. Credit: Gregory Breese/USFWS

As if that weren’t bad enough, ocean acidification and warming coastal waters are affecting other foods the rufa red knot eats. Young blue mussels are an important prey species for rufa red knots. But warming ocean temperatures have shrunk their range, and the mussel soon may not be available as a food resource for migrating rufa red knots at another important stopover in Virginia.

It is a similar story in the Arctic breeding areas. Insects are hatching earlier due to warmer temperatures, and this could cause knot chicks to miss the peak window for feeding and rapid growth before their long migration south.

So it isn’t just that the restaurants are closed; the grocery stores could close, too. …Finish reading this on our national Open Spaces blog!

 

One Comment on “Climate change could leave the rufa red knot hungry

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