The lowest-quality of identifiable images possible. Very distant record shots (e.g., mile-distant digiscopes), very grainy, small-in-the-frame, and out of focus images. Barely identifiable.
Fairly poor images. Not very sharp, poorly lit, and/or much of the bird obscured. Fills a fairly small portion of the frame, but not tiny.
Mid-quality images. Fairly sharp, decently lit (e.g., dappled lighting, partially backlit), a busy background (e.g., branches), is partially obscured, and doesn’t fill very much of the frame.
Images that are quite good, but not fully 5-star worthy. This rating will likely span many of the “good” photos. 4-star photos are ones that have a bird that is pretty sharp, but might have mediocre lighting (e.g., sidelit), is partially obscured in a tree, and doesn’t quite fill the frame. It is still a solid photograph, but just not the top quality.
The best images possible; one with a bird that fills the frame, is sharp and well-lit, has a clean background, and is posed well.
The comments section below the media is different than the one attached to the entry for that species. Media comments refer to that specific image or recording, whereas the species comments refer to that entire observation, which is often not just the bird that you photographed or recorded. This is a subtle yet important difference; the media comments are attached to the image, and the species comments attached to the observation.