ECOLOGICAL CORRELATES OF MOLT IN MERLINS (FALCO-COLUMBARIUS)

The energetic requirements of breeding can affect the ability of a bir d to simultaneously undergo replacement of its feathers. From 1987 to 1994 we examined patterns of wing- and tail-feather molt in 286 Merlin s (Falco columbarius richardsonii) captured in Saskatoon, Saskatchewan during the breeding season to investigate the relationship between th ese two events. Female Merlins had significantly higher molt scores th an males, but among a variety of environmental variables, only capture date was significantly correlated with the extent of molt in female M erlins. In contrast, molt in male Merlins was correlated with capture date, the quality of the nest place, and the hatching date of the chic ks. Nearly one-half of all males examined had an arrested molt pattern (i.e. molt stopped partway through), while less than 30% of females h ad arrested molt. Differences between the sexes may be related to thei r roles in reproduction. The fact that male Merlins provide most of th e food for the pair and their young during the breeding season apparen tly necessitates slowing down and in some cases arresting molt. Female s appear to arrest molt due to the greater demand of having more chick s.