“A bird in the hand is worth two in the bush,” also sometimes given as, “A bird in the hand is better than two in the bush,” is a proverb saying that it is better to stick with something you already have, rather than pursuing something you may never get. This proverb is a very popular warning, widely used in many English-speaking countries.
The phrase seems to have originated at some point in the 13th century, in a related Latin form: Plus valet in manibus avis unica quam dupla silvis. This can be loosely translated as, “A bird in the hand is worth more than two in the woods.”
The basic warning of this saying is that you must take care not to get too greedy in life. If you are holding a bird in the hand, you have your meal for the evening. You can take that one bird, and be well fed. If instead you let it go to pursue two birds you’ve spied in a bush, you may catch neither, and wind up hungry for the night. This proverb points out that by passing up a sure thing for a more promising possibility, you also run the risk of losing both the sure thing and the promising possibility.
The saying may be used to refer to any number of things, in many different situations in life. Since the core concept is one of staying away from greed, it is often very apt. In gambling, for example, a person who has won a fair amount of money and wants to bet it all once more might be reminding that he has already made a profit, and by pursuing even more money, he may lose it all.
The concept demonstrated by the proverb can be looked at more closely using a game theory analysis. In this, we would have to also examine the probability of catching the two birds in the bush. Then we could begin to better calculate the relative values of the bird in the hand, and the bird in the bush. Different strategies would then manifest themselves: an extremely cautious strategy would of course always keep the known quantity, even if the chance of catching the two birds in the bush was 99%; a balanced strategy might advocate keeping one bird as long as the chance of catching the birds in the bush was less than 50%; and an extremely bullish strategy would always go for the two birds in the bush.
Some people also respond to this proverb, not necessarily accepting the wisdom that a bird in the hand is in fact better than two in the bush. People who respond are usually pointing out that while something that is known and possessed might be certain, the unknown could have a value far exceeding the known. A response might be something like, “a bird in the hand is good, but a bird in the bush might sing.”