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THE WILSON JOURNAL OF ORNITHOLOGY • Vol. 124. No. 2. June 20/2 
relatively unimportant by-product of this process 
in terms of energy expenditure. This likely is the 
basis for the position of Howell et al. (2003). but it 
seems premature to modify the conventional 
definition of ’molt’ on this basis in the absence 
of supporting evidence. Use of the term ’pre- 
juvenal molt' to refer to all acquisitions of juvenal 
plumage (e.g., Pyle 2008. Howell 2010) generally 
appears reasonable, however, and I use this 
approach except where the context otherwise 
requires (see Definition of the First Molt Cycle: 
page 415), 
PrejuvenaJ Molts and Juvenal Plumages 
Howell et al. (2003) presumed prejuvenal molts 
and juvenal plumages were homologous across 
species but, other than noting that prejuvenal and 
definitive prebasic molts typically are complete, 
they did not provide any analysis or evidence to 
support their conclusion that prejuvenal molts and 
juvenal plumages arc basic in nature and presum¬ 
ably homologous with definitive prebasic molts 
and basic plumages. Humphrey and Parkes 
(1959), by starting their analysis of plumage 
succession with the loss of juvenal plumage, 
appeared to consider the prejuvenal molt unique 
and not basic in nature even if it is homologous 
across species. At least four factors support this 
position. 
First, as noted by Howell and Corben (2000), 
the prejuvenal molt is, by necessity, a more 
complete, temporally compressed, and synchro¬ 
nous molt than definitive prebasic molts, which 
may be incomplete in many species, including 
most raptors, eolumbids, cuculids. owls, nightjars, 
trogons, kingfishers, and woodpeckers (Jenni and 
Winkler 1994; Pyle 1997. 2008). Definitive 
prebasic molts, unlike prejuvenal molts, may vary 
significantly in duration and be suspended for 
phases of breeding, migration, or nutritional stress 
(Humphrey and Parkes 1959, Payne 1972). 
Second, as acknowledged by Howell et al. 
(2003), the prejuvenal molt produces a unique 
plumage for most birds because juvenal body 
feathers typically are structurally weaker than 
feathers grown in subsequent molts (Jenni and 
Winkler 1994, Pyle 1997, Butler et al. 2008), 
Moreover, juvenal feathers frequently differ from 
basic leathers in length, shape, pattern, and color 
(Alatalo et al, 1984, Jenni and Winkler 1994, 
Butler et al. 2008. Moreno and Soler 2011). Third, 
many taxa do not have a natal down plumage that 
is replaced by juvenal feathers (Jenni and Winkler 
2004) and acquire juvenal plumage, unlike basic 
and other plumages, without shedding feathers. 
Fourth, several factors suggest conventional first 
prebasic molts and first basic plumages are 
homologous with definitive prebasic molts and 
basic plumages. The foregoing considerations 
suggest prejuvenal molts and juvenal plumages 
are appropriately named and distinguished from 
prebasic molts and basic plumages even if these 
molts and plumages are homologous, as seems 
likely. 
The status of the prejuvenal molt is unknown in 
the absence of a complete physiological under¬ 
standing of molt. However, Howell et al. 1 2003) 
essentially conceded the validity of the conven¬ 
tional approach to this molt when they evaluated 
the best way to address the ‘first basic problem'. 
Having concluded it is inappropriate to start the 
first moll cycle with the conventional first 
prebasic molt because it is variable in timing 
and extent and not basic in nature. Howell et al. 
(2003) believed they had to make a choice. They 
could align moll cycles by considering the 
complete prebasic molt at the end of a bird's first 
molt cycle to be the first prebasic molt, or they 
could consider this molt the second prebasic molt 
as is conventional for most birds and deem the 
prejuvenal molt the first prebasic molt. Howell et 
al. (2003: 642) selected the second option, not 
because the prejuvenal molt is clearly basic in 
nature and they could not have chosen the first 
option, but because choosing the first option 
“would result in a major upheaval of convention¬ 
al terminology' Thus, the change in the conven¬ 
tional view of prejuvenal molts and juvenal 
plumages was an expedient way for Howell et 
al. (2003) to address the ‘first basic problem' and 
not based on scientific evidence. 
First Prebasic Molts and Basic Plumages 
Perhaps the most important modification to the 
H-P system proposed by Howell et al. (2003) was 
the change in the identity of the conventional first 
prebasic molt to a unique preformative molt 
because it is highly \ariable in timing and extent 
within and across species. Howell et al. (2003) 
maintained the conventional first prebasic molt i> 
not homologous with subsequent prebasic molts, 
and is a nonrecurring adaptation that allows birds 
to get through their first molt cycle. However, 
some species have a uniformly-complete conven¬ 
tional first prebasic molt that is equivalent in 
liming with definitive prebasic molts and produc- 
