“And he shall sprinkle” — sprinklings by non-kohanim are invalid. A fortiori: a bird for which the Torah already required a Kohen for melikah certainly requires a Kohen for hazayah.
In the sugya: The Gemara derives that the hazayah of the bird-chatas must be performed by a Kohen. Because the Torah already required a Kohen for the preceding melikah, a kal va-chomer establishes the same requirement for the sprinkling.
Type of Learning
Kal va-chomer from melikah to hazayah — only a Kohen may sprinkle the blood.
What Is Learned
Only a Kohen may sprinkle the blood of the bird-chatas. A non-Kohen invalidates the service. The requirement is not merely preferential; it is indispensable, derived by a fortiori from the Kohen requirement already stated for the melikah of the same bird.