atiel Honking?

This has happened a lot to my atiel (named Dodo since it is the first word he could say, and he only responds to that) and my vet diagnosed it as a sinus infection, as you have guessed. Replace his water with orange juice diluted 2:1 with water. Also, try placing some cut up orange peel (about 5mm X 5mm squares) and mix it with his seeds.