Nazir 3 - Proximity search
If a person says, "I take on myself an obligation to bring birds (sacrifice) - this also serves as a declaration that he is becoming a nazir. Since, talking about Nebuchadnezzar, Daniel says that " His hair has grown like the feathers of an eagle ", the person does a mental proximity search and, finding the two words "hair" and "eagle" (bird) close, he means the hair of a nazir when he refers to birds - this is the opinion of Rabbi Meir. The Sages, however, say that he is not a nazir, because people do not do such proximity searches in their heads.
This explanation is hard to accept though - not everybody is so knowledgeable. It could be that nobody does such searches. Rather, the man meant those birds that a nazir needs to brings if he becomes ritually impure - and this explains why Rabbi Meir says that he becomes a nazir. But perhaps he meant to pay for the bird sacrifice for someone else, but not become a nazir himself? - We have to say that a nazir was passing in front of him.
The Sages, however, consider all these explanations of the point of view of Rabbi Meir as forced, and say that the man does not become a nazir by promising a bird sacrifice.
Art: Exotic Pheasants and Other Birds By Charles Collins