My fiance, Toby, & I adopted an African Senegal from Craigslist about 2 days ago. ... My question about biting is the fact that Cracker (the parrot) will do a kind of fake out, then bite. For example, about 5 mins ago, I walked slowly up to his cage talking to him with my hand held like a perch, saying "step up." He didn't show that he was going to bite me immediately (opens his mouth wide & goes for me), but as soon as he put a foot on my hand, he bit me! ... I've found that if I'm trying to get him to step up and he wants to bite, that if I put my other hand behind him & "herd" him towards the hand to step up, he won't bite. Thoughts?
Congratulations in your Senegal.
How old is he?
First of all you want to try to avoid being bitten. It's really easy to accidentally reinforce a bite so you need to try as hard as you can to avoid the bite in the first place because when biting is reinforced the bird will very quickly learn to bite to get what it wants and it's very hard to "un-teach" learned biting.
You said he showed no signs before he delivered a bite and while this is possible it's more likely he did
show some signs that were overlooked. Look for eye pinning, raised feathers around the beak or on the nape of the neck, or any other body language that indicates aggression and if you see it, back off. Alternately look for positive signs indicating he wants to step-up such as lifting a foot as you approach him.
If he is literally not showing any sign of biting or aggression but bites when he steps up that means that "step-up" was forced on him in the past and he learned over time to suppress all signs of aggression in regards to "step-up" and that is kind of a scary situation. Sometimes a Poi will just sit perfectly still like a statue just waiting to bite as soon as the hand is in range but this is a learned behavior.
A common misconception for a new bird owner is that a bird MUST OBEY the step-up command AT ALL TIMES and that makes it into a dominance thing and birds do not respond well to dominance (meaning they respond with aggression). Don't "herd" him because this further enforces the idea that step-up is about dominance. He needs to have a choice and the right to say "no." If he doesn't want to step-up there is no reason to force him to do so unless it's some kind of emergency and you have to evacuate your house or something. Leave him alone for a few minutes and try again.
A bird is not like a dog which independently seeks out interaction with people and you need to use a different approach. The best thing you can do is use positive reinforcement to show him that good things happen when he steps up. If he knows he is going to get a reward for stepping up and/or that good and fun things happen after he steps up he will rarely if ever refuse to step-up or bite. If you are not familiar with using positive reinforcement to teach a behavior see Michael's Taming and Training Guide