BirdLife International has a good summary of recent problems with red knot conservation. Some of the issues they list are familiar:
Although the causes of the population crash are not yet fully understood, the dramatic decline is mainly attributed to the low availability of horseshoe crab eggs in Delaware Bay, USA, a key stopover site for Red Knot Calidris canutus rufa. The lack of eggs has been attributed to an elevated harvest of adult crabs for bait in the conch and eel fishing industries. Studies show that Red Knot individuals with lower body weight at departure in Delaware Bay have lower survival than heavier birds.And one I had not read about:
Even if crab exploitation ceases immediately, scientist predict it would take years before the horseshoe crab population recovers to its former level. Other possible contributing factors in the decline include the loss of critical habitats, contamination and the spread of non-controlled tourism activities at their wintering and migration areas.
In April, 312 dead Red Knot Calidris canutus rufa were discovered by a park guard at Playa La Coronilla in northern Uruguay and the same day over 1,000 birds were found dead at a second site nearby. Of the events Joaquín Aldabe, IBA coordinator at Aves Uruguay (BirdLife in Uruguay) commented: "It seems possible that harmful algal blooms could be related to it, although additional studies are required in order to fully understand this unexpected event."If a substantial portion of the subspecies can die off so suddenly, the bird really needs protection.
Aves Uruguay, in connection with other national and international organisations, is already working in the area to establish the possible causes of the casualties and the role of Uruguay as stopover for the species.
“The death of more than 1,300 Red Knots in Uruguay is of particular concern given the low overall population size,” said Rob Clay, Conservation Manager of BirdLife’s Americas Secretariat. “This number represents over 6% of the [rufa] population, all of which winter in southern South America. The discovery underlines the need to better understand factors which may be affecting the species during migration and on its wintering grounds.”