isn't rational or winged [specific differences] just Quality?
You seem to be arguing for or implicitly assuming monism*, as though there were only one substance called "being" and the differences between substances really accidental or illusory.
Quality is an accident, but specific differences (differentiæ) pertain to substance and essence.
cf. this chart of categories
St. Thomas Aquinas distinguishes substantial or essential differences from accidental differences, showing that the former is known by the latter, as cause is known by its effect:
De Ente et Essentia, cap. 4:
For even in the case of sensible things, the essential differences themselves are not known; whence they are signified through accidental differences which rise out of the essential ones, as a cause is signified through its effect
In rebus enim sensibilibus etiam ipsæ differentiæ essentiales nobis ignotæ sunt, unde significantur per differentias accidentales, quæ ex essentialibus oriuntur, sicut causa significatur per suum effectuum
cf. the other quotes in this answer to the question "We know substances by means of their accidents?", which discuss differentiæ.
*Monism is false because change exists, pace Parmenides; cf. Part II of Essence & Topicality of Thomism.