Data from: Malar stripe size and prominence in peregrine falcons vary positively with solar radiation: Support for the solar glare hypothesis ...

• Main Authors: Vrettos, Michelle, Reynolds, Chevonne, Amar, Arjun
• Format: Dataset
• Language: English
• Published: Dryad 2021
• Subjects: FOS Biological sciences; Canada; Stripe; Falco peregrinus
• Online Access: https://dx.doi.org/10.5061/dryad.b8gtht7c9; https://datadryad.org/stash/dataset/doi:10.5061/dryad.b8gtht7c9

Many falcons (Falco spp.) exhibit a distinct dark plumage patch below the eye, termed the malar stripe. This stripe is hypothesised to reduce the amount of solar glare reflected into the eyes while foraging, thereby increasing hunting efficiency in bright conditions. Here, we use a novel, global-scale correlative approach to test this “solar glare hypothesis” in peregrine falcons (Falco peregrinus), the most widespread falcon species, using web-sourced photographs from across the species’ global range. We found that the size and prominence of the malar stripe were positively associated with average annual solar radiation, but not with other environmental variables, such as temperature and rainfall. Our results provide the first published evidence for the hypothesis that this plumage feature functions to reduce the amount of solar glare reflected into the falcon’s eyes, thereby improving the ability to pinpoint and target agile prey in bright conditions. ... : Photograph metadata for user-submitted photographs of peregrine falcons (including the name of the photographer, date and location at which the photograph was taken, GPS coordinates, photographer comments, and sex and subspecies identification) were downloaded from the Macaulay Library (https://www.macaulaylibrary.org/) and iNaturalist (https://www.inaturalist.org/) online databases, using the websites' export tools. All photographs were then downloaded using the list of image URLs and filtered to include only adult birds correctly identified as peregrine falcons. For each country represented in the photograph metadata (and for each state or province, in the case of the USA and Canada), a random selection of 50 photographs was then chosen for analysis. This selection process was repeated until the maximum number of 50 usable photographs for each country or state was reached, or until there were no more photographs available. Data on average annual solar radiation (W/m2), average annual rainfall (mm) and ...