The respiratory system influences flight mechanics in soaring birds

The subpectoral diverticulum (SPD) is an extension of the respiratory system in birds that dives between the primary muscles responsible for flapping the wing. Surveying the pulmonary apparatus in 68 species showed that the SPD was present in virtually all soaring taxa investigated yet absent in non-soarers. We find that this structure independently evolved with soaring flight at least seven times, indicating that the diverticulum may have a functional and adaptive relationship with this flight style. Using the soaring hawks Buteo jamaicensis and B. swainsoni as models, we show that the SPD is not integral for ventilation, that an inflated SPD can increase the moment arm of cranial parts of the pectoralis, and that pectoralis muscle fascicles are significantly shorter in soaring hawks than in non-soaring birds. This coupling of an SPD-mediated increase in pectoralis leverage with force-specialised muscle architecture produces a pneumatic system adapted for the isometric contractile cond..., , , # **README document for the dataset from**: Schachner et al., 2024. The respiratory system influences flight mechanics in soaring birds. Nature. [https://doi.org/10.5061/dryad.0k6djhb64](https://doi.org/10.5061/dryad.0k6djhb64)

**Description of the data and file structure**

This dataset includes the files and code used to re-run the character correlation analyses from the manuscript. It also includes the surface files that were used to model the moment arms for the biomechanical analysis of the pectoralis models of the Red-tailed and Swainson’s hawks. These models should be opened and run using GaitSym 2019. The link for this free software is listed below. Lastly, there is a zipped file of high-resolution images (TIFF image files), showing each of the birds scanned for this project. They are the original images used in the extended data section of this manuscript.

The following files are provided:

1\)        Input files and code necessary to run the character correlation analyses in...