The accuracy of field sex determination in the Common Whitethroat Sylvia c. communis

JONAS WALDENSTRÖM & ULF OTTOSSON The accuracy of field sex determination of Common Whitethroats captured during spring migration in Nigeria was tested with a genetic sex determination technique. Among both age classes males were more often correctly sexed than females. In total, one out of four birds were incorrectly sexed, and the ability to sex correctly varied considerably between ringers. Hence, a cautious attitude must be held at all times towards the use of field sex assessment in Common Whitethroats. Jonas Waldenström, Ottenby fågelstation, Pl 1500, S-380 65 Degerhamn, Sweden and Animal Ecology/EBC, Norrbyvägen 18D, S–752 36 Uppsala, Sweden. Ulf Ottosson, Department of Animal Ecology, Ecology Building, S-223 62 Lund, Sweden; present address 18A, rue de Mamer, L-8280 Kehlen, Luxemburg. Received 10 February 2000, Accepted 22 February 2000, Editor: S. Bensch