Confuciusornis is a genus of four to six known pigeon-sized theropods (at least two may represent the same species) from Jurassic China that appear to be more closely related to true birds than Archaeopteryx is. They are the oldest-known birds with beaks instead of scaly snouts, they have no teeth, and they have a pygostyle instead of the long bony dinosaur-like tail. They have very long pointed wings and asymmetrical flight feathers, making them altogether more like modern birds than any other known creature of their time, but skeletons indicate they weren't capable of powerful flapping flight and may instead have been gliders.
Fossils of this genus have been found in vast quantities, and places where entire flocks of hundreds of birds were preserved simultaneously have been found. They are so abundant that long before they were known to science, several hundred had been collected and sold in Chinese street markets - and this, in fact, is how the first Confuciusornis to be described in the scientific literature was initially found. The colors in this drawing are accurate, but the pattern is not - I was able to find several references that they were gray, brown, orange/red, black, and white, and that the wings were mostly white, but I couldn't find anywhere that showed the exact pattern of how these colors were laid out on the body.