Horus, Ra - Falcon
Horus - as a god - came before Ra. Horus also had a falcon head. The etymology of the name Horus and the word haru - falcon - appear to be the same.
The suggestion is that the falcon flies high, is the king of the birds, sees all. Horus is king of the gods of Egypt/patron god of Egypt. Later sometimes fused with Ra - the newly introduced god of the sun as Egypt moved in the direction of monotheism.
One Egyptologist that I read said something like this...
Horus and Ra aren't the same god but the Egyptians sometimes became confused and would associate one with another... maybe because different times and areas of Egypt preferred one over the other but a chief god was desired and also because they were both associated with the falcon. (This should mess up the questioner because now the answer is circular!)
It's fairly complicated, and we don't know it all. Interestingly, Horus had 2 eyes... the eye of the sun and the eye of the moon.
Horus He was often depicted as a sphinx with the head of a man (like the Great Sphinx of Giza), or as a hieracosphinx, a creature with a lion's body and a falcon's head and wings,
Ra was portrayed as a falcon and shared characteristics with the sky-god Horus. At times the two deities were merged as Ra-Horakhty, "Ra, who is Horus of the Two Horizons". In the New Kingdom, when the god Amun rose to prominence he was fused with Ra as Amun-Ra.
The Eye of Horus symbolism