Data collection (Aim 1)
For the first aim of my study (to evaluate the ubiquity of changes to
the flight apparatus of captive birds) I measured study skins at the
Australian National Wildlife Collection, Australian Museum, American
Museum of Natural History, Harvard Natural History Museum, Museum of
Victoria, South Australian Museum and the Tasmanian Museum and Art
Gallery. I assigned individual provenance (captive/wild) based on
specimen metadata. Captive specimens were rarer in museum collections –
I aimed for at least five captive and wild specimens per species, so
some species were excluded. I selected common species in zoological and
private collections because, like multi-generational
conservation-focused captive-breeding programs, specimens were likely to
be captive-born (not wild-collected). Although I previously showed that
wing shape change in orange-bellied parrots was independent of
generations of captive breeding (Stojanovic et al. 2021), I aimed
to minimize this risk by using older captive-bred specimens that were
less likely to be multi-generational captive-bred (however, the
individual histories of captive-born specimens in this study were
unknown). The mean collection date of captive specimens was 1955 vs.
1938 for wild specimens, reflecting the emergence of Australian
avicultural trapping and trade last century (Franklin et al.2014). Species inclusion was limited by (i) collection bias toward
attractive Australian native species which are preferred in captivity
(Vall-llosera & Cassey 2017), and (ii) for non-Australian species,
absence of wild specimens for comparison.
Using electronic calipers (0.01mm) and rulers (1mm) I measured: wing
chord (LW), the length of the most distal secondary
feather (LS), the length of the longest primary feather
(LP) (per Jenni & Winkler 1989), the distance between
the tips of the outermost eight primary flight feathers (P10-P3) to the
tip of the longest primary feather (i.e. ΔQ, per Lockwood et al.1998). P10 is the most distal flight feather that forms the leading edge
of the wing, and P3 is the most proximal flight feather I measured. In
passerines p10 is vestigial (Hall 2005) and I did not measure this
feather. However, to improve visualization and interpretation of the
results, I relabel P9 of passerines as P10 because this is the most
distal functional flight feather in non-passerines. Our sample included
16 species from three families (Table S1): Phasianidae, n=1 sp.;
Estrildidae, n=6 spp.; Psittaculidae, n=9 spp. I aimed for equal sex
ratios (final sex ratio: 127 males, 123 females, 116 unknown) and the
total sample comprised 146 captive-born specimens and 220 wild-born
specimens.