DOI: 10.5061/dryad.5qfttdz3q
title: Overlap in the wing shape of migratory, nomadic and sedentary grass parrots

description: Bird wing shape is highly correlated with mobility, and vagile species
 have more pointed wing tips than sedentary ones. Most studies of bird wing
 shape are biased to the northern hemisphere, and consider only two
 migratory syndromes (north-south migrants or sedentary species). There are
 major gaps in knowledge about the wing shapes of different taxa with other
 movement strategies (e.g. nomads) in the southern hemisphere. Parrots are
 a prominent southern hemisphere bird order with complex movement patterns,
 but their wing shapes are mostly unstudied. We test whether three metrics
 of wing shape of grass parrots (Neophema and Neopsephotus spp.) correspond
 to their purported migration syndromes (and other factors). We show that
 two strongly migratory grass parrots and an arid-adapted nomad had pointed
 wings, with flight feather longer distally and shorter proximally.
 However, purportedly sedentary species overlapped extensively with
 migrants and nomads in all aspects of wing shape, and taxonomic
 relationships, purported migratory syndromes and ecological barriers did
 not explain the variation we recorded. The most distantly related species
 (Neopsephotus) had most dissimilar wing shape to the others, but broadly
 conformed to the expectations of long pointed wings of a nomad. Why
 purportedly sedentary grass parrots had unexpectedly pointed wings is
 unclear. We propose the hypothesis that this wing shape may persist in
 sedentary populations if individuals experience strong but intermittent
 selection to disperse when environmental conditions are poor. If pointed
 wings are not costly during good times when individuals are sedentary,
 this wing shape may persist in populations as a ‘back up’ in bad times.
 Our study highlights the interesting migration patterns in the southern
 hemisphere that remain largely unstudied. Wing shape offers an interesting
 way to identify potentially undiscovered capacity for movement in data
 deficient species, which may also have implications for conservation.
description: We present data from 54
 orange-bellied parrots, 46 blue-winged parrots, 30 elegant parrots, 31
 rock parrots, 31 scarlet-chested parrots, 34 turquoise parrots and 32
 Bourke’s parrots. There was a roughly even split between sexes in data for
 each species. We 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. The mean collection date was 1946
 (range: 1857 – 2016), and because museum skins stop shrinking after three
 years (Harris 1980, Green 1980) specimen age was unlikely to influence our
 study.   Specimens were measured using electronic
 calipers (to the nearest 0.01mm) and a thin, soft plastic ruler (1 mm). We
 measured: (1) LW - unflattened wing chord, (2) unflattened length of the
 longest primary flight feather (measured from the point where the calamus
 inserted into the skin – we followed (Jenni and Winkler 1989) to measure
 the length of feathers), (3) ΔQ values (following the method of Lockwood
 et al. 1998, including the feather numbering system where p1 forms the
 leading edge of the wing), i.e. distances between the tip of each primary
 flight feather from the tip of the longest primary feather, and (4) SL -
 the distance between the carpal joint and the tip of the most distal
 secondary on the folded wing. These measurements are illustrated in
 Supplementary Materials Figure S1. We excluded juveniles (identified from
 specimen tags and metadata), specimens with broken or worn flight
 feathers, and specimens where the wings were not in the resting position.
 Because suitable wild-born specimens of all species (particularly
 orange-bellied parrots) were scarce in museum collections, we included
 some birds that had individual missing feathers (p4 – p8), and estimated
 the ΔQ value as midway between the two feathers adjacent the gap. We
 excluded birds missing p1 – p3. Either p9 or p10 were missing in 19 skins
 in our sample, so to minimize impacts on our sample size, we only included
 ΔQ1 – 8 values in the analysis and thus included these skins in the study.
 DS took all the measurements and quantified measurement error using a
 subset of repeat-measured birds. Measurement repeatability was high, and
 observer error accounted for mean 12.6 % of variance across the traits
 measured (range: 5 – 23%).  Additional information about the data and the
 species involved is provided in the paper.