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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 4. December 2012 
ic factors (Payne 1972); remigial molt sequence 
may be based on either neurophysiological events 
(Voitkevich 1966, Rohwer et al. 2011) or an 
endocrinological mechanism (Miller 1941. Bridge 
2011). That two Rufous Fantails in our study 
switched front a center at P 1 during one molt 
episode to a center at P ? or P 4 during the next 
episode suggests the sequence may be phenotyp¬ 
ical ly plastic and adaptive based on environmental 
as well as genetic factors. 
Regular molt centers other than P 1 have been 
documented among Eurasian passerines, most 
thoroughly for Brown Shrikes (Lanins cristatus; 
Stresemann and Stresemann 1971, Cramp and 
Perrins 1993) and Savi's Warblers (Thomas 1977. 
Cramp 1992. Neto and Gosler 2006); a few other 
individual cases in other passerine species have 
been reported (Jenni and Winkler 1994. Thomp¬ 
son and Kilaysky 2004). possibly representing 
anomalies or based on injuries. Most Brown 
Shrikes appear to have a center between primaries 
4 and 3 (molt proceeding both distally and 
proximally), but some have either a single or a 
second center at primary I. Other Lanins shrikes 
appear to have a normal distal sequence from P I 
in all individuals (Cramp and Perrins 1993). 
Commencement of primary replacement can be 
variable in Savi's Warblers with some birds 
having a distal sequence from P I and others 
appearing to have centers among primaries 2 and 
6; birds initiating the prebasic molt at P I tended 
to commence molt earlier than those initiating 
molt among primaries 2-6 (Neto and Gosler 
2006). 
Rutous Fantails with molt centers among 
primaries 2-4 showed no apparent seasonal pattern 
within our capture periods (Feb-Aug). However, a 
complete assessment of seasonality would have to 
account for annual breeding phenology (which 
appears to vary between years; P. Radley and J. F. 
Saracco. pers. comm.) as well as age and gender 
variation m timing of molt; we Currently lack the 
data to address this question. The greater proportion 
of younger (SCB) and female Rufous Fantails with 
a medial molt center compared to older birds and 
males suggests they may have a selective advantage 
in foraging that affects the molt commencement 
point. Neto and Gosler (2006) did not separate 
younger from older individuals in their study 
s, milar age-specificity suggesting slower or later 
molts in younger birds could indirectly explain the 
tendency for medial molt centers to occur with 
later-molting Savi's Warblers. 
Multiple series in larger birds, constrained from 
replacing all primaries in a single molting season, 
allows more feathers to be replaced in a shorter 
period without creating large gaps in the wing, 
thereby maintaining wing-surface integrity and 
greater ability to fly and forage (Tucker 1991. 
Hedenslrom and Sunada 1999, Rohwer 1999. Pyle 
2005). Our results suggest a center among 
primaries 2-4 in younger and female Rufous 
Fantails may have evolved as an alternate strateg) 
in groups with a selective foraging disadvantage to 
enable them to replace more primaries more 
rapidly while maintaining better foraging ability. 
However, direct correlation with wing loading 
(mass and wing chord) was not evident in our study 
alter controlling for effects of age and gender. 
It may be advantageous for younger and female 
fantails to have multiple molt series iT they are 
under greater time or energetic constraints due to 
poorer foraging ability or greater breeding con¬ 
straints. respectively. Female passerines may 
initiate molt later than males on average because 
males abandon their broods and mates in favor of 
early molting (Svensson and Nilsson 1997, 
Hemborg and Merila 1998); this could result in 
the need for more rapid molting in breeding 
lemale tantails, perhaps varying regularly on an 
inter-annual basis. Rapid molt may be unusual in 
tropical climates, where time constraints arc less 
severe than in temperate climates (Ryder and 
Wolfe 2009). Our results suggest an adaptation for 
rapid replacement in some short-winged passer¬ 
ines that rely on flight to forage for aerial insects, 
such as Rufous Fantails (Higgins et al. 2006). 
Molt sequence among inner primaries is 
difficult to document unless specifically looked 
loi because molt among inner primaries is rapid 
and few specimens have been collected at this 
stage (Pyle 1997). It is possible multiple series 
may occur more often than suspected among 
passerines. Molt sequence is especially poorly 
documented in tropical passerines (Rvder and 
Wolfe 2009), and discovery of additional tropical 
passerines with multiple molt series may shed 
further light on the evolution and adaptation of 
this strategy. We encourage further study to 
document molt sequence among inner primaries 
ol passerines, and to investigate evolutionary’ 
causes for variation within and among species. 
ACKNOWLEDGMENTS 
thank Paul Radley for providing funding and 
immense logistical support for the TMAPS stations on 
