The Wilson Journal of Ornithology I 24(4):682-687, 2012 
TWO MODES OF PRIMARY REPLACEMENT DURING PREBASIC 
MOLT OF RUFOUS FANTAILS, RHIPIDURA RUFIFRONS 
JAMES H. JUNDA. 1 - 2 ANDREA L. CRARY.' AND PETER PYLE' 
ABSTRACT.—We documented unusual variation in the sequence of primary replacement during the prebasic molt of 
Rufous Fantails (Rhipidura rufifrons ) captured in 2009 and 2010 on Saipan. Northern Marianas Islands. Most captures 
(62%) followed a typical replacement sequence, starting at the proximal primary (P I) and proceeding distally to the 
outermost primary (P 10), but some individuals (38%) commenced molt from medial leathers, either P 2. P 3. or P4 with 
replacement proceeding bidirectionally from the point of origin in multiple molt series. The distribution of centers for 
medtal origin was P 2 (3%), P 3 (77%), P 3 and/or P 4 (12%), and P 4 (8%), indicating this pattern was distinct from the 
typical (PI) pattern and the commencement point was not fixed to a specific primary, females and individuals undergoing 
the second prebasic molt were more likely to have a center among primaries 2-4 than males and older birds. Two females 
that showed a center at P I during molt in 2009 showed a center at P 3 or P 4 during molt in 2010 represented exceptions to 
this finding hut also indicated the starting point could vary inter-annually in an individual. Multiple molt senes among 
p..manes are poorly documented in passerines and we provide the first evidence for this molting strategy in the 
Rhtpidundae. Our results suggest a molt center among primaries 2-4 in younger and female Rufous Fantails niav have 
evolved to enable more-rapid replacement ol primaries while maintaining belter foraging ability among selectively 
disadvantaged individuals. Received 20 January 20/2. Accepted II May 2012. 
Molt sequence among primaries of passerine 
birds is largely fixed, replacement beginning 
with a center at the innermost primary (P I) and 
ptoceeding distally in a single series to the 
outermost feather (P 9 or P 10). Prcformalive 
molt can be incomplete and eccentric in some 
species with molt commencing at a primary other 
than P 1. but replacement continues to be distal 
and in sequence (Pyle 1997). Multiple molt 
centers or series among primaries have been 
documented widely among non-passerine families 
including albatrosses (Diomcdeidae). alcids (Al- 
ctdae), falcons (Falconidae). parrots (Psitlacidae), 
and owls (Strigidae) (Miller 1941; Langston and 
Rohwer 1995; Pyle 1997, 2008; Thompson and 
Kitaysky 2004,. but only a few exceptions to 
distal and sequential replacement during complete 
prebasic molts have been documented in north- 
temperate passerines. The primaries of Spotted 
Flycatchers (Muscicupa striata; Muscicapidae) 
are replaced proximally (generally from P 10 to 
P 1) and. in a few European shrikes (Laniidae) 
and warblers (Lucostellidae), primary molt can 
begin with medial primaries and proceed bidirec¬ 
tionally, displaying multiple molt series (Cramp 
1992. Cramp and Perrins 1993, Jenni and Winkler 
1994). American Dippers (Cinclus mexicanus- 
Cincltdae). among North American passerines 
have been reported to molt primaries out of 
sequence commencing with a block of medial 
leathers (Sullivan 1965). We are unaware of other 
North American or tropical passerines that 
diverge Irom a single distal replacement series. 
Multiple molt series are thought to be an 
adaptation lor increased foraging efficiency in 
birds with time constraints for molting (Tucker 
1991, Hcdenstrom and Sunada 1999. Pyle 2005, 
Rohwer ct al. 2009); documentation of exceptions 
within families may lead to a better understand¬ 
ing ol remigial-replacement strategies (Rohwer 
1999), 
Rufous Fantails ( Rhipidura rufifrons; Rhipi- 
duridae) occur in Australia, Indonesia, and 
islands of the southwestern Pacific Basin (Hig¬ 
gins et al. 2006). This passerine species is 
insectivorous with short rounded wings and 
icites heavily on aerial foraging strategies. We 
discovered some Rufous Fantails molting bi- 
direclionally from a center among primaries 2.3, 
oi 4 during research on the demography of 
landbirds on Saipan. Northern Marianas Islands 
(Radley et al. 2011). Other individuals displayed 
a sequence more typical of passerines, com¬ 
mencing with P 1 and proceeding distally to P 
10. Our objective is to document variation in the 
primary replacement sequence of Rufous Fan- 
tails on Saipan and discuss its possible evolu¬ 
tionary implications. 
' The Institute for Bird Populations, P. O. Box 1346 METHODS 
Point Reyes Station, CA 94956, USA Ri • 
"Corresponding nndior; ™u : jam e sJunda .g raai , com Aprf| ° P "7o " 
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