The red knot is a medium-sized shorebird that undertakes one of the longest migrations in the animal kingdom. In recent decades, the rufa subspecies of red knot has faced a severe population decline primarily due to habitat degradation and declines in horseshoe crab populations, a main food source. This has led to the red knot being listed as threatened under the Endangered Species Act. But when exactly did the red knot become endangered?
What are red knots?
Red knots are shorebirds in the genus Calidris. There are 6 subspecies of red knot: roselaari, rogersi, canutus, piersmai, rufa, and islandica. They are about 9-11 inches long with a wingspan around 20 inches. Their plumage is typically gray and reddish in breeding season. Red knots breed in the Arctic and subarctic regions and undertake long migrations to coasts in the southern hemisphere. Their diverse diet includes insects, marine invertebrates like mollusks and crustaceans, plant matter, fish, and eggs.
Key facts about red knots:
- Genus: Calidris
- Length: 9-11 inches
- Wingspan: Around 20 inches
- Plumage: Gray and reddish in breeding season
- Range: Arctic and subarctic breeding, southern hemisphere coasts in winter
- Diet: Insects, mollusks, crustaceans, plants, fish, eggs
Why are red knots endangered?
The main factor in the decline of the rufa subspecies of red knot is the degradation of key habitats they rely on during their migrations. They stopover at just a few key sites along their journey between the Arctic and South America. Damage and disturbances to these habitats has severely impacted their numbers. For example, the dredging of Delaware Bay has negatively affected horseshoe crab populations there, a main food source for migrating red knots.
Major threats to red knots:
- Habitat degradation at migration stopover sites
- Declines in horseshoe crab populations, an important food source
- Human disturbance at beaches and intertidal areas
- Climate change impacts on Arctic ecosystems
- Overharvest of shellfish food sources
The dependence of red knots on just a few key stopover sites makes them very vulnerable to these habitat threats. With their numbers plummeting, the rufa subspecies was listed as threatened under the Endangered Species Act in 2015.
Population trends of red knots
The rufa subspecies of red knot has faced severe population declines in recent decades. Surveys at key wintering and stopover sites and population modeling indicate a dramatic reduction in their numbers.
| Year | Estimated Population |
|---|---|
| 1980s | 150,000-200,000 |
| 2000s | 50,000-100,000 |
| 2010s | Around 25,000 |
This represents an estimated 75% drop in the total rufa red knot population from the 1980s to the 2010s. The declines have been linked to the threats outlined earlier. Without improved protection of migration habitats, the subspecies may face extinction.
Key population survey and monitoring sites:
- Delaware Bay – Spring migration stopover
- Rio Grande, Argentina – Wintering grounds
- Tierra del Fuego, Chile – Wintering grounds
When was the red knot listed as threatened?
In September 2014, the U.S. Fish and Wildlife Service officially listed the rufa subspecies of red knot as threatened under the Endangered Species Act. This designation went into effect in December of that year after a standard waiting period.
Listing the red knot as threatened makes it illegal to hunt, harm, or otherwise “take” the bird without a permit. It also requires federal agencies to ensure any activities they authorize, fund, or carry out will not jeopardize the species further. A recovery plan is being developed for the red knot.
Key events leading to threatened status:
- 2005 – Listed as candidate species for ESA protection
- 2011 – Proposed formally for threatened status
- September 2014 – Final threatened status approved
- December 2014 – ESA protections take effect
This threatened listing under the Endangered Species Act was an important step in protecting the rufa red knot from extinction. However, full endangered status may be warranted if populations continue to decline despite conservation efforts in the years ahead.
Ongoing conservation efforts
Many conservation groups and agencies are working to protect and restore red knot populations. Efforts include habitat restoration at migration sites, addressing threats to food sources, establishing protected areas, and working with industries and communities to reduce disturbances.
Examples of conservation actions:
- Restoring Delaware Bay beach and horseshoe crab habitats
- Working with South American communities to reduce mollusk harvesting
- Reducing human disturbances like beach vehicles
- Monitoring and adaptive management of subsistence harvests
- Increasing Arctic breeding area protections
International cooperation is also critical, since red knots migrate between hemispheres. Continued monitoring of red knot populations will help assess if these actions are enough. More habitat protections and reduction of threats may be needed to stabilize and recover red knot numbers.
Conclusions
The rufa subspecies of red knot has faced severe population declines since the 1980s primarily due to habitat degradation at migration stopover sites. Estimates indicate a 75% drop, from around 150,000-200,000 to just 25,000 birds in the 2010s. In 2014, the rufa red knot was listed as threatened under the Endangered Species Act in the United States.
Ongoing conservation efforts aim to restore critical habitats, reduce disturbances, monitor populations, and build international cooperation to save the red knot. But habitat protections and threat reductions may need to be expanded to stabilize the declining population. Without more successful conservation measures, the red knot may need to be uplisted to endangered status in the future.
The story of the red knot highlights the importance of protecting critical migration habitats for threatened migratory species. Their epic journeys rely on just a few sites that provide food and rest. Conservation of these habitats is crucial to giving an endangered migratory species like the red knot a fighting chance.
