IntroductionCaptive animal phenotypes can diverge from the ideal ‘wild type’, and these changes can affect behavior, morphology and physiology (Crates et al. 2022). However, the specific nature and combination of ‘captive phenotypes’ can vary widely between species (Crates et al. 2022). Whether changes are important depends on the intended use of captive-bred animals. For display animals, phenotypic changes may be inconsequential. Conversely, conservation breeding programs – a globally popular tool to combat species extinctions (Conde et al.2011) – should ideally produce animals optimized for life in the wild after release, but this more easily said than done (Taylor et al.2017). If altered captive phenotypes incur a fitness cost in the wild, conservation breeding may be less effective than hoped (Crates et al. 2022). Thus, it is important that conservation breeding programs quantify optimal wild phenotypes, and be vigilant of changes arising from life in captivity that might jeopardize survival after release (Shier 2016; Berger-Tal et al. 2020).Phenotypic changes to traits involved in strenuous or high-risk phases of life history may be disproportionately important for fitness post release from captivity. For example, migration is a high-risk behavior that strongly selects for the most capable individuals (Dingle 2014; Rotics et al. 2016). Captive-born animals are often less successful migrants than wild-born conspecifics (Crates et al.2022). This is sometimes attributable to behavioral differences. For example, some captive-born birds depart later and travel shorter distances than wild conspecifics (Burnside et al. 2017), and captive-bred butterflies fail to orient themselves or even attempt migration (Tenger-Trolander et al. 2019). Morphological changes also likely contribute to poor migration outcomes post release, but evidence for their effects on fitness is surprisingly limited. Davis et al. (2020) recently showed that captive-bred monarch butterflies Danaus plexippus have differently shaped wings and lower migration success than wild conspecifics. Wing shape strongly predicts flight efficiency (Lockwood et al. 1998; Sheard et al.2020). Given that migratory birds are commonly bred in captivity for reintroduction (Davis 2010; Burnside et al. 2017; Hutchins et al. 2018; Stojanovic et al. 2020b; Tripovich et al. 2021), quantifying the ubiquity of deleterious captive wing shape phenotypes and their post-release fitness consequences is critical information.I aimed first to compare captive/wild wings of 16 species representing three commonly captive-bred bird families (Phasianidae, Psittacidae, Estrildidae) to evaluate the ubiquity of captive wing shape phenotypes. Then, using a critically endangered migratory bird as a model, I aimed to demonstrate that a captive wing shape phenotype incurs a fitness cost post release.
