Legolas is capable of accurately detecting danger from within the woods

It was not long before Aragorn found fresh signs. At one point, near the bank of the Entwash, he came upon footprints: hobbit-prints, but too light for much to be made of them. Then again beneath the bole of a great tree on the very edge of the wood more prints were discovered. The earth was bare and dry, and did not reveal much.

‘One hobbit at least stood here for a while and looked back; and then he turned away into the forest,’ said Aragorn.

‘Then we must go in, too,’ said Gimli. ‘But I do not like the look of this Fangorn; and we were warned against it. I wish the chase had led anywhere else!’

‘I do not think the wood feels evil, whatever tales may say,’ said Legolas. He stood under the eaves of the forest, stooping forward, as if he were listening, and peering with wide eyes into the shadows. ‘No, it is not evil; or what evil is in it is far away. I catch only the faintest echoes of dark places where the hearts of the trees are black. There is no malice near us; but there is watchfulness, and anger.’

‘Well, it has no cause to be angry with me,’ said Gimli. ‘I have done it no harm.’

‘That is just as well,’ said Legolas. ‘But nonetheless it has suffered harm. There is something happening inside, or going to happen. Do you not feel the tenseness? It takes my breath.’

‘I feel the air is stuffy,’ said the Dwarf. ‘This wood is lighter than Mirkwood, but it is musty and shabby.’

‘It is old, very old,’ said the Elf. ‘So old that almost I feel young again, as I have not felt since I journeyed with you children. It is old and full of memory. I could have been happy here, if I had come in days of peace.’

‘I dare say you could,’ snorted Gimli. ‘You are a Wood-elf, anyway, though Elves of any kind are strange folk. Yet you comfort me. Where you go, I will go. But keep your bow ready to hand, and I will keep my axe loose in my belt. Not for use on trees,’ he added hastily, looking up at the tree under which they stood. ‘I do not wish to meet that old man at unawares without an argument ready to hand, that is all. Let us go!’

The Two Towers, Book Three, Chapter 5: The White Rider.