This is a derivative work based on the image here (see Gallery below). The file has been reduced in size and the image lightened in LCH space, a colour space designed to approximate the visual experience. The purpose was to lighten the image without affecting the hue and saturation of its colours. The tool used was the AutoContrast edit in LCH space in Nikon's Capture X2 image processing software.
Original public domain image from Wikimedia Commons