Discordancy of two common methods of measuring feather hydrophobicity

Feather structure contributes greatly to a birds’ ability to repel water, which is essential for thermoregulation and energy use. Water repellency of feathers has traditionally been inferred by measuring a structural index based on the distance between the feather radii and vane. A more direct method measures the contact angle of a water droplet resting on the pennaceous vane. This method is used for measuring the water repellency of various materials (e.g., textiles) and we considered it a standard against which the structural index can be validated. Despite widespread use of both techniques, their level of agreement with each other has not been systematically evaluated. Additionally, few studies have tested the direct contribution of uropygial oil to a feather’s water repellency. We tested the correlation between the two methods, using feathers from two high-elevation species that are adapted to the cold and wet conditions of montane systems, Swainson’s Thrush (Catharus ustulatus) and..., , , # Data from: Discordancy of two common methods of measuring feather hydrophobicity

Dataset DOI: [10.5061/dryad.ncjsxkt67](10.5061/dryad.ncjsxkt67)

## Description of the data and file structure

**Experimental context & data description:**

The attached raw data explains the values found when measuring contact angles of water droplets on contour feathers of Swainson's Thrushes and Bicknell's Thrushes, both before and after washing the feathers to remove any dirt and/or preen oil. This data was collected to answer the experimental hypotheses, which was that Bicknell's Thrushes feathers were more hydrophobic than Swainson's Thrushes. We included an analysis with and without preen oil to understand if this substance had hydrophobic qualities. All analyses were done in RStudio, and readers may request the code by emailing [[e-mail]](mailto:[e-mail]). The data is organized in a .xlsx file, with columns for each variable explained below.

#### File: Raw\_Data.xl...,