No support for solar radiation as a major evolutionary driver of malar stripes in falcons

The malar stripes of falcons (Falco spp.) are often hypothesised to function by reducing the amount of solar glare reflected into the falcon’s eyes while hunting, thereby aiding foraging efficiency in bright conditions. This “solar glare hypothesis” is supported by intraspecific trends in Peregrine Falcons (Falco peregrinus), in which populations inhabiting regions of higher average annual solar radiation exhibit larger and darker malar stripes on average. Here, we extend the methodological approach previously used in Peregrine Falcons to examine both intra- and interspecific relationships between solar radiation and malar stripe morphology across all extant falcon species, thereby providing a more robust test of the hypothesis that falcon malar stripes evolved as an adaptation against negative visual effects of solar glare. We obtained web-sourced photographs of all extant falcon species, taken across each species’ geographic range, and related mean breeding season solar radiation at e...,
Photograph metadata for user-submitted photographs of 39 falcon species (including the name of the photographer, date and location at which the photograph was taken, GPS coordinates, photographer comments, and species, sex, and subspecies identification) were downloaded from the Macaulay Library (https://www.macaulaylibrary.org/) and GBIF (https://www.gbif.org/) online databases, using the websites' export tools, with additional photographs sourced from Flickr (https://www.flickr.com), Oiseaux (https://www.oiseaux.net), BirdGuides (https://www.birdguides.com), the African and Oriental Bird Club Image Databases (currently hosted at https://africanbirdclub.org/afbid and https://www.macaulaylibrary.org/oriental-bird-images/, respectively), and private photographers via email correspondence. All photographs were then downloaded using the list of image URLs and filtered to include only photographs of adult birds and those taken within the breeding or resident range for the species..., , # No support for solar radiation as a major evolutionary driver of malar stripes in falcons

[https://doi.org/10.5061/dryad.gxd2547wq](https://doi.org/10.5061/dryad.gxd2547wq)

## Description of the data and file structure

The data file contains photograph metadata for user-submitted photographs of 39 falcon species (including the name of the photographer, date and location at which the photograph was taken, GPS coordinates, photographer comments, and species, sex, and subspecies identification) from the Macaulay Library ([https://www.macaulaylibrary.org/)](https://www.macaulaylibrary.org/\)), GBIF ([https://www.gbif.org/)](https://www.gbif.org/\)), Flickr ([https://www.flickr.com](https://www.flickr.com)), Oiseaux ([https://www.oiseaux.net](https://www.oiseaux.net)), BirdGuides ([https://www.birdguides.com](https://www.birdguides.com)), the African Bird Club Image Database ([https://africanbirdclub.org/afbid](https://africanbirdclub.org/afbid)), and the Oriental Bird Club Image Databa...