A male turkey vulture (possibly him, but unnamed) first appeared to deliver Jackie's message (landing on Martin's head in the process) in the very first episode "The Nose Knows," where the Kratt brothers checked out his wings and, more importantly, his nose. Chris added that a turkey vulture has the best sense of smell than any animal in the world, and that you can see right through his nostrils.
An unnamed turkey vulture (simply called a bird) appeared in "Who's in the Hole?". When Zoboomafoo thinks that Flying Squirrel's skin between her arms helps her fly like a bird, and Martin not really, the vulture flew in and landed on Chris' head. When Martin and Zoboo saw this, Chris said that Flying Squirrel doesn't flap like a bird does, pointing to the vulture on his head. Martin then explains that a flying squirrel glides. Zoboo then understands that a bird flaps (the turkey vulture flaps its wing as Zoboo flaps his arms), and a squirrel glides. After that, the vulture jumps off Chris' head and flies out of Animal Junction. Zoboo states that the bird is flapping away as it does. Chris tells him that he guess that he can say that and asks Martin if he's right, before wondering where he is.
A unnamed female turkey vulture (not Tomatohead) delivered the message in "Ears Hear." The Kratts heard her loud flapping and stated that they didn't need their Super Ear Sensers to hear it. Zoboomafoo saw the vulture, but couldn't see her ears and wondered where they are. Martin pointed out that the turkey vulture's ears were the holes in the sides of her head behind the eyes.
Another unnamed turkey vulture delivered a message in "Horses," also landing on Martin's head. The vulture's wings were also complimented.
More turkey vultures (none were named so it is unknown if Tomatohead is among them) appeared in "Flying Buddies."
Tomatohead delivered the message from Amy in "Fearfest", where Chris states that some people think that turkey vultures are scary. He may also be the vulture that attended the Fearfest.