Radagast the Brown??

[SarumanCymraeg]

Even though Radagast can be deemed to failure, it has been suggested (although I'm not sure if Tolkien himself said so explicitly) that Radagast was responsible for the Eagles' coming at certain appropriate times (such as the Battle of the Morannon and Five Armies).

Of the Blue Wizards, Tolkien came to theorise that they did not, in fact, fail in their mission, but were fundamental in helping some in the East resist Sauron. If they had not gone East, then Sauron's influence there would be much stronger and he would be able to muster a much stronger army to conquer the West.

[mormegil]

Two quotes on the blue wizards

In 1954 he was uncertain about the Blue Wizards, but in a letter of 1958 he says of them "I fear that they failed, as Saruman did, thought doubtless in different ways; and I suspect they were founders or beginners of secret cults and 'magic' traditions".

--The Letters of J.R.R. Tolkien, p.280

However, in The Peoples of Middle-Earth they get a happier ending; they "must have had great influence on the history of the Second Age and Third Age in weakening and disarraying the forces of [the] East".

-- The Peoples of Middle-Earth, p.385

So it seems that Tolkien himself was divided. But it should not be forgotten that he said in unfinished tales

of all the Istari, one only remained faithful

Even though Radagast can be deemed to failure, it has been suggested (although I'm not sure if Tolkien himself said so explicitly) that Radagast was responsible for the Eagles' coming at certain appropriate times (such as the Battle of the Morannon and Five Armies).

Rather I think Gwaihir was responsible for these actions and Radagast had little to do with the actually movement of deep events in Middle-earth.

[Snowdog]

Could it be said that Radagast's knowledge taught Sarumann to use the crows as spies?

[Inziladun]

Originally Posted by Snowdog

Could it be said that Radagast's knowledge taught Sarumann to use the crows as spies?

Actually, I think it was likely Radagast himself who was directing the birds and animals to spy and report to Saruman, on the latter's orders. Saruman doesn't seem to have had the skill, or desire, to make nice with lesser creatures.

I suspect Radagast never cottoned to Saruman's betrayal, else he'd have taken some active part against him. I think Radagast just wandered around, blissfully unaware of what was really going on. Radagast probably still thought Saruman was an ally, and that helping Saruman with information gathering was his bit in the fight against Sauron.

[Faramir Jones]

Inziladun, I think you're being unfair on Radagast here:

Originally Posted by Inziladun

I suspect Radagast never cottoned to Saruman's betrayal, else he'd have taken some active part against him. I think Radagast just wandered around, blissfully unaware of what was really going on. Radagast probably still thought Saruman was an ally, and that helping Saruman with information gathering was his bit in the fight against Sauron.

We should remember that when Radagast gave Gandalf Saruman's message to go to Isengard, Gandalf suspected absolutely nothing. Saruman, though doing his own thing, was still thought to be an ally. That this was a widely held feeling can be seen at the Council of Elrond, when the truth was told.

[Inziladun]

Originally Posted by Faramir Jones

We should remember that when Radagast gave Gandalf Saruman's message to go to Isengard, Gandalf suspected absolutely nothing. Saruman, though doing his own thing, was still thought to be an ally. That this was a widely held feeling can be seen at the Council of Elrond, when the truth was told.

Certainly Radagast can't be blamed for trusting Saruman at the time he advised Gandalf to go to Isengard.
But what about after? R. wasn't at the Council of Elrond. The scouts from Rivendell went to Rhosgobel and couldn't find him. It doesn't appear Gandalf ever spoke with him again, at least not until after the War was over. If Radagast never figured out (or, as I think, was never fussed enough about the War against Sauron to really care) that Saruman had turned to evil, there's no reason he wouldn't have kept telling the animals and birds to bring news to Saruman.

[Faramir Jones]

In answer to your question:

Originally Posted by Inziladun

But what about after? R. wasn't at the Council of Elrond. The scouts from Rivendell went to Rhosgobel and couldn't find him. It doesn't appear Gandalf ever spoke with him again, at least not until after the War was over. If Radagast never figured out (or, as I think, was never fussed enough about the War against Sauron to really care) that Saruman had turned to evil, there's no reason he wouldn't have kept telling the animals and birds to bring news to Saruman.

What we have makes it clear that Radagast was negligent in pursuing the mission. Tolkien, in his essay on the Wizards in Unfinished Tales, said that of them 'only one[Gandalf] remained faithful'; and Radagast 'became enamoured of the many beasts and birds that dwelt in Middle-earth, and forsook Elves and Men, and spent his days among the wild creatures'.

However, Radagast didn't go over to evil, as Saruman did; so I certainly don't agree that he would have carried on helping him once he knew the true state of affairs. I'm sure that Gwaihir, after he rescued Gandalf from Orthanc, would have given him this new information about Saruman.