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A Talk on the Wild Side.

Climate Change Could Leave the Rufa Red Knot Hungry

rufa red knot
A tagged red knot searches for food at Mispillion Harbor, Delaware. Photo Credit: Gregory 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. 

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.  

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.” 

rufa red knot
Red knots feed around a horseshoe crab at Mispillion Harbor, Delaware. Photo 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.

And that’s just looking at the climate change issues related to food. Other potential climate issues related to habitat include changes to:

  • The Arctic tundra ecosystem (e.g., predators, vegetation) where the knots breed.
  • Coastal habitats due to rising sea levels.
  • Storm and weather patterns. 

To be sure, the rufa red knot faces other challenges. Horseshoe crabs are used in the medical industry and in the fishing industry, and crab overharvest in Delaware Bay previously was a central issue affecting knot populations. Harvests are now being managed, but ensuring a healthy balance of knots and crabs in the future remains a top conservation priority. Coastal development can threaten the bird, too, as can off-road vehicle use and other human activities that disturb birds. 

Protecting the rufa red knot under the Endangered Species Act (ESA) is a critical step toward recovering this species.  The ESA includes regulatory protections that help reduce the “take” of listed species, and requires federal agencies ensure the actions they conduct, authorize or fund are not likely to result in jeopardizing the species, and to take actions that contribute to conservation.  in particular, listing paves the way for preparing and implementing a recovery plan to identify and guide actions for conserving the species so that in the future it t will no longer need protection under the ESA.  Thus listing provides a means for federal, state, local and private organizations and landowners to enhance cooperation and coordination of conservation efforts for the species and its habitats.  While the effects of  climate change pose new and complex threats for this and many other species, the Service is working with partners to reduce risks and increase resiliency of our valuable natural resources, as outlined in the collaborative National Fish, Wildlife and Plants Climate Adaptation Strategy.

-- Matt Trott, External Affairs

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