Why do few Afro-Siberian Knots Calidris canutus canutus now visit Britain?

The nominate (Afro-Siberian) subspecies of the Knot Calidris canutus canutus breeds on the Taimyr Peninsula in Siberia and occurs commonly in the westernmost Wadden Sea during migration to West and South Africa. The recoveries and controls of 2045 Knots ringed in Britain and Ireland provide no evidence for canutus wintering there nor for their regular passage during autumn and spring migration. Five juveniles ringed in the first week of September 1963 were recovered in Africa between eight and 37 days later, and another two birds ringed at the same time (one as an adult) showed up in subsequent years in Spain and Germany at times typical for Afro-Siberian Knots. There haz,e been no comparable bursts of southern recoveries since. The period in 1963 driving which the Afro-Siberian juveniles were captured on the Wash tons characterized by sustained wind patterns conducive to bringing naive juvenile waders from the Siberian tundra to the southwest. Such conditions have been increasingly rare in later years. The paucity of recent records may Additionally reflect a decline in this population. Juveniles leading Siberia would probably fly a constant compass course to western Europe, a flight of more than 5000 km logically ending in southeastern England. The scarcity of Afro-Siberian type recoveries based on Knots ringed a mere 350 km (five to sis hours of flight) west of the Wadden Sea is therefore remarkable.