Below are high-resolution images of photos that I have used under the Creative Commons license, and detailed information about each work.
Mallards Anas platyrhynchos in Castle Park, by Flickr user postman.peter. Licensed under the CC BY 2.0. Source: Flickr. Used at the peer-reviewed research page.
Little rush warbler Bradypterus baboecala Cedara Farm, Pietermaritzburg, South Africa, by Alan Manson. Licensed under the CC BY-SA 2.0. Source: Flickr. Used at the peer-reviewed research page.