1 Steve: {leaping out of his hospital bed} I'm feelin' bonza, Terry. Let's go film some crocs!
1 Terry: Jane said no crocs, Steve.
2 Steve: Alligators, then?
2 Terry: No.
2 Steve: Coral snakes?
2 Terry: No.
3 Steve: Taipans? Brown snakes?
3 Terry: No.
3 Steve: {increasingly desperate} Komodo dragons?!
4 Terry: Jane drew up a list of banned reptiles. In fact... it's a list of all reptiles...
4 Steve: Crikey!

When I was growing up, the major groups of significantly sized animals were mammals, birds, reptiles, amphibians, and fish. (Insects, worms, and so on were less important than the "big" animals.) Reptiles were basically defined as cold-blooded, egg-laying animals with waterproof skins (smooth or scaly). Birds were clearly a completely different kettle of snakes - they had feathers and warm blood, and flew.

But even at a young age, it was clear that something odd was going on here. I had experience with parrots, and chickens, and they had scaly legs and feet that resembled the skin of a reptile.

In more recent years, there has been something of a revolution in taxonomy, based on several startling finds in the fossil record. The gist of it is that the traditional definition of "reptile" has fallen by the wayside as a useful scientific classification. This is because the evolutionary family tree of the amniotic animals began with early reptile-like species. These diversified into a line that led to the mammals, and a line that led to what we generally consider the reptiles. All modern reptiles descended from these early reptile forms - but so did all the birds. The birds represent a tiny little twig at the far end of a great branching set of different reptiles. In other words, if we want to have an evolutionarily useful definition of "reptile", we have to include the birds in it.

The traditional reptiles are thus what is known as a paraphyletic group, which is better explained at Wikipedia than by me writing a whole lot more stuff.

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2016-03-29 Rerun commentary: So, just to be clear, Jane Goodall's list does prohibit Steve from interacting with birds too.

Also, to be clear, Jane's prohibition is not to protect Steve in his delicate recovery phase, but to protect the animals.