The Red-billed Chough can be confused with the Yellow-billed Chough, although the Red-billed Chough is the only corvid with an intensely red bill and legs. Similarly, the Yellow-billed Chough has a yellow bill and is slightly smaller.
The plumage of both sexes is very similar, so sexing through plumage is very difficult. In extreme cases, size can be a useful variable to differentiate males from females, with the latter being slightly smaller in wing, bill, and tarsus. Many of the individuals cannot be sexed due to the overlap in this species.
It is possible to recognize 3 different ages:
Juvenile specimen: they have new plumage, meaning there is no apparent wear. The color of the legs is orange, the bill is between yellow-orange, and the iris is dark gray or almost black.
1st to 2nd year specimen: the wing and tail still maintain juvenile feathers that in this time have a little more wear and present a black-brownish color that makes the lesser secondary coverts and body feathers stand out, which have been molted and now present the bright black color of the adult.
Adult specimen: the entire plumage is bright black and with little wear on the wings and tail. The bill, tarsus, and legs are intense red and the iris, unlike the juvenile specimen, is brown-reddish.
The Red-billed Chough adult birds undergo a complete post-nuptial molt that usually ends in the month of October. On the other hand, the one-year-old individuals undergo a partial post-juvenile molt in which they change their body feathers and lesser coverts, in certain individuals there may be a molt of some of the median coverts.
Primaries: 10 per wing.
Secundaries: 9-10 per wing.