I haven't birded either of those but if you bird the North East section, get a guide. Don't try that section on your own as it is too dangerous with critters (large and small) always around the birding areas. I know when my birding pal and I went out to the outback area in Melbourne , we encountered a poisonous one up in our wheel well, as well as a few poisonous ones just walking around. Do not bird any of the outback or marshes alone, as even the birding pals will tell you that...don't do it if you are not sure of the area. Just my sage....jim
Okaaaay. That is strange advice.
I have lived in Australia for coming up 11 years. As well as birding I have bush-walked and trail run in bush areas regularly.
Whoever was bigging up the dangerous critters was pulling your leg I think. I have barely ever seen snakes. Yes, snakes are common, especially in spring / summer throughout most of the country, but they are shy and your chances of encountering one are fairly slim (there is no 'outback area in Melbourne' by the way, not even within several hours drive!) When surveying critters in the outback of NW New South Wales and Queensland and actively trying to find snakes we struggled.
Tiger snakes can be aggressive if you catch them out, but generally most snake species will know you are coming before you know they are there and scoot out of the area. Some of the sea snakes are dangerous but unlikely to be encountered birding
Crocs are a risk in the far north of Queensland and the Northern Territory if you wander to close to creeks /waterholes / mangroves. I assume this was driving the not birding 'marshes' comment?
Generally though 'critters' are unlikely to be a risk if you are even vaguely aware and sensible. Unless you are a small / medium sized mammal / reptile / bird.
The outback (true outback - dirt / sand road, often 100s of km / miles between small towns, little traffic, infrequent fuel / water supplies, roads impassible in wet weather) is a serious proposition and shouldn't be entered into lightly, this is true. But there is heaps of country and heaps and heaps of birding without going near these areas.
Not sure what North East section means. Far North Queensland? A great birding area and absolutely doable without a guide in many areas near Cairns / Townsville etc., you'd only need help going north of Cooktown IMHO. I have birded there solo and with 1 or 2 friends a few times.