Figure Legend
Figure 1. A theoretical evolutionary approach to moult in birds
from reptiles, using the four moult strategies defined by Howell et al.
(2003; see also Howell 2010). The phylogenetic tree is based primarily
on that of del Hoyo & Collar (2014, 2016) with some revisions to
reflect recent systematic advancements (see Supporting information file
for the use of this tree during times of phylogenetic flux). The four
strategies are Simple Basic (SBS; no preformative or prealternate
moults), Complex Basic (CBS; a preformative moult but no prealternate
moults), Simple Alternate (SAS; a single moult in the first cycle and
prealternate moults in later cycles), and Complex Alternate (CAS; a
preformative moult in the first cycle and prealternate moults in all
cycles). Here we propose that both prebasic and preformative moults, and
hence the Complex Basic Strategy (purple lineages in the figure), are
ancestral to all modern birds, although further study is needed on when
preformative moults evolved in primitive avian taxa or reptiles
ancestral to birds. Prealternate (and presupplemental) moults have
evolved many times along different lineages and should not be considered
homologous. See Supporting information file for an expanded version of
this phylogenetic tree (Fig. S1) along with detailed explanation and
discussion.