A comparative study of post‐juvenile moult in four species ofSylviawarbler

Post‐juvenile moult in relation to dispersal and migration in the ChiffchaffPhylloscopus coltybita

“…The sequence of post-juvenile moult in the Chiffchaff is basically similar to other warbler species previously studied (Norman 1981(Norman , 1990. However, commencement, extent and duration of moult is more similar to that of the Blackcap Sylvia atricapilla than of the Willow Warbler Phylloscopus trochilus, Garden Warbler S.borin, Whitethroat 5. commuais or Lesser WhitethroatS.cum/ca.…”

“…Body weight in relation to stage of moult was also analysed. During July -October 1980to 1990 Chiffchaffs caught in Cleveland, north-east England were examined for post-juvenile moult. Of these 27 were examined twice and 4 three times.…”

Dispersal and site fidelity in Lesser WhitethroatsSylvia curruca

“…Dispersal in Chiffchaffs Phylloscopus cotybita occurs before the commencement of postjuvenile moult (Norman 1991). This difference is probably caused by speciesspecific start times in post-juvenile moult: Chiffchaffs do not commence moult until an age of 55 days whilst Lesser Whitethroats start some 27 days earlier (Norman 1990(Norman ,1991, so that young of both species are the same age when dispersal occurred. Less than 3% of birds ringed in moult stages 5-6 (49+ days old) were recaptured in the same season.…”

“…Moult/migration of this type has also been recorded for other species of long-distance migrants (Norman 1981, Boddy 1983, Ellegren 1990). In Cleveland body mass during moult stages 5-6 are similar to pre-moult weights (Norman 1990) and would allow only short stage overnight flights to staging areas on the south coast of England (Mead 1983). The only recovery/control during the 20 year study concerned a young bird ringed at Dungeness, Kent in September which was captured in the following summer breeding in the study area.…”

“…A small population of Lesser Whitethroats has bred at my study site in north-east England since 1972 and during the past 20 years data have been collected on certain aspects of their annual biological cycle (Norman 1990). This paper concentrates on dispersal of juvenile birds in relation to post-juvenile moult, and on site fidelity of breeding adults.…”