Red Knot migration reaches Cape May Observatory [View all]

Brian Kushner

The rufa Red Knot's spring migration is timed to coincide with the horseshoe crab's spawning season, as the massive outlay of eggs provides a rich, easily digestible food source for the exhausted birds. Delaware Bay shores provide the single most important spring stopover area for the Red Knot, hosting within a narrow time window up to 90 percent of the North American population. Other key U.S. stopover sites include coastal islands off Georgia, South Carolina, Virginia, and Massachusetts.

When preparing for spring migration, Red Knots pack on extraordinary amounts of weight to fuel their long flights. When they reach the Delaware Bay, exhausted and emaciated, the birds must regain fat they lost in the first leg of their journey, and pile on even more. Often, Red Knots almost double in weight while feasting on protein-rich horseshoe crab eggs, before continuing northward and breeding soon after Arctic arrival. During these periods, these birds exhibit among the highest rates of mass gain of any vertebrate.


Martin Pelanek

The rufa subspecies migrates along the East Coast of the United States. In spring, it depends upon a major Mid-Atlantic rest stop, where ancient sea creatures congregate and sustain these birds during their long journey.

Beginning in the 20th century, horseshoe crab overharvest, paired with coastal development and sea-level rise, began to take a serious toll, and rufa Red Knot numbers declined about 75 percent from the 1980s to the 2000s.

American Bird Conservancy has successfully advocated for horseshoe crab harvest restrictions in Mid-Atlantic states and for the creation of a horseshoe crab sanctuary at the mouth of Delaware Bay. New Jersey has, for 12 years running, maintained a moratorium on any horseshoe crab harvests, while Delaware, Maryland, and Virginia now ban capture of females and shut down their seasons once a quota is reached on males.

https://abcbirds.org/bird/red-knot/