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.