DOI: 10.5061/dryad.rn420
title: Data from: Flight reconstruction of two European enantiornithines (Aves, Pygostylia) and the achievement of bounding flight in Early Cretaceous birds

description: Birds today follow different aerial strategies to deal with the high costs
 of flapping flight. Intermittent flight, through either flap-gliding or
 bounding, is commonly used among small birds as a strategy to optimize
 aerial efficiency. The broad morphological disparity of the different
 lineages of Mesozoic birds suggests that a range of aerial strategies
 could have evolved early in avian evolution. Based on biomechanics and
 aerodynamic theory, this study reconstructs the flying properties of two
 small enantiornithines from the Lower Cretaceous fossil site of Las Hoyas
 (Spain), Concornis lacustris and Eoalulavis hoyasi. Our results show that
 the short length of their wings in relation to their body masses were
 suitable for flying through strict flapping and intermittent bounds, but
 not through facultative glides. Aerodynamic models indicate that the power
 margins of these birds were sufficient to sustain bounding flight. Our
 results thus suggest that C. lacustris and E. hoyasi would have increased
 aerial efficiency through bounding flight, just as many small passerines
 and woodpeckers do today. Intermittent bounding appears to have evolved
 early in the evolutionary history of birds, at least 126 million years
 ago.
description: Appendix S1. Concornis
 lacustris and Eoalulavis hoyasi measurements.Measurements of the
 fossil specimens from Las Hoyas included in the present study. Following
 Serrano et al. (2017).Appendix
 S1.docAppendix S2. Modern
 birds' dataset.Dataset of modern
 Neoaves used in the present study. Main flight modes were assigned
 following Viscor and Fuster (1987), Del Hoyo et al. (1992; vol 1-16) and
 Bruderer et al. (2010). Specimen code: Only number – Burke Museum of the
 University of Washington (Seattle, USA); UBCBM – Beaty Museum of the
 University of Bristish Columbia (Vancouver, Canada); BR – obtained from
 the dataset of Bruderer et al. (2010); VF - obtained from the dataset of
 Viscor and Fuster (1987); PN – obtained from the preset database of
 software Flight 1.24.Appendix
 S2.csvAppendix S3. Summary of
 Canonical Variates Analysis.Summary of Canonical
 Variates Analysis: 1. Eigenvalues and % variance explained by the
 canonical functions; 2. Lambda Wilk’s test for mean groups’ differences;
 3. Coefficients of the canonical functions; 4. Reclassification of modern
 birds’ dataset after leave-one-out validation. Group codes: continuous
 flapping (1); bounding (2); facultative gliding (3).Appendix
 S3.docAppendix S4. Difference
 in power margin between two modern birds with similar body
 mass.Flight reconstruction of
 two modern flying birds with similar BM to show difference in the power
 margin. Power curves indicating the relationship between Pmec and Vt were
 modeled for a continuous flapping strategy (i.e., q=1) with CDb calculated
 according the two approaches used in this study: A, CDb = 0.1; and B, CDb
 = 0.01 SL / Sb (see Methods). Pav is closely similar as both birds
 weighted almost the same, and thus the mean value of Pav was drawn
 (pointed horizontal line). The bar-tailed godwit Limosa lapponica (BM =
 367g; CDb = 0.136) shows sufficient power margin to sustain flapping
 flight in the full-range of Vt, using the aerobic activity from the flight
 muscles. In contrast, the grey partridge Perdix perdix (BM = 372g; CDb =
 0.125) cannot sustain a prolonged flapping flight because the Pav does not
 attain Pmec. Instead, partridges and other Galliformes fly using short
 bursts supported by anaerobic activity of the fiber muscles (see Bishop
 and Butler 2015).Appendix
 S4.doc