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Not AvailableThis study investigates the evolution of locomotory morphology and migratory behavior in nightingale-thrushes (genus Catharus), a clade of songbirds with diverse migratory strategies. With large datasets of molecular and morphometric characters, we resolve phylogenetic relationships, identify and model migration-related morphological characters, and estimate ancestral states of those characters to infer evolutionary transitions in the migratory phenotype. While acknowledging that unknown factors (e.g., differential extinction) may confound interpretation, our results suggest that (1) migratory behavior and its functional morphology are fundamentally linked; (2) short-distance or elevational migration (not long-distance) was the ancestral state of Catharus; (3) short-distance migration was the evolutionary precursor of long-distance migration; and (4) the short-distance migrant, Hermit Thrush (C. guttatus), may be in relative phenotypic (ecological) stasis. This potentially explains the ecological incumbency of C. guttatus in temperate North America during winter, and offers a new framework for interpreting the evolutionary sequence that produced long-distance migration in this model system. 

Abstract Hawks, eagles, and their relatives (Accipitriformes: Accipitridae) are a diverse and charismatic clade of modern birds, with many members that are instantly recognized by the general public. However, surprisingly little is known about the relationships among genera within Accipitridae, and several studies have suggested that some genera (in particular, the megadiverse genus Accipiter) are not monophyletic. Here, we combine a large new dataset obtained from ultraconserved elements, generated from whole genome sequencing of 134 species, with publicly available legacy markers (i.e. a suite of commonly sequenced mitochondrial and nuclear genes) to infer a well-supported, time-calibrated phylogeny of 237 extant or recently extinct species. Our densely sampled phylogeny, which includes 90% of recognized species, confirms the non-monophyly of Accipiter and provides a sufficient basis to revise the genus-level taxonomy, such that all genera in Accipitridae represent monophyletic groups.