A bird in the hand is worth two in the bush
It's better to have a lesser but certain advantage than the possibility of a greater one that may come to nothing.
Origin - the short version
This 16th century proverb is one of the oldest and best-known in English. It warns against taking unnecessary risks - it is better to keep what you have (a bird) than to risk getting more and ending with nothing (two birds out of your reach).
Origin - the full story
This proverb, like many others, warns against taking risks and suggests that you should keep what you have and not risk losing it by going after more. The other reading of the meaning is that it refers to medieval falconry where a bird in the hand (the falcon) was a valuable asset and certainly worth more than two in the bush (the prey). It may well be that both of these meanings were intended by the coiners of this proverb, which may go some way to explaining why it has resonated over the centuries and is still in common use.
This proverbial saying is first found in John Heywood's 1546 glossary A dialogue conteinyng the nomber in effect of all the prouerbes in the englishe tongue:
Better one byrde in hande than ten in the wood.
It's probable that Heywood didn't coin the expression himself but by how long the phrase pre-dates his publication isn't clear. Interestingly, the next line in Heywood's book (which is form in rhyming couplets) is another of the best known proverbs - "Rome was not bylt on a daie (quoth he) & yet stood".
Variations of the proverb existed prior to 1546, for example, this piece from Wycliffe's Bible, 1382:
Ecclesiastes IX - A living dog is better than a dead lion.
Variants that explicitly mention birds in hand come later. The earliest of these is in Hugh Rhodes' The Boke of Nurture or Schoole of Good Maners, circa 1530:
"A byrd in hand - is worth ten flye at large."
Or, as the Czechs have it, 'a sparrow in the fist is better than a pigeon on the roof'.
The expression fits well into the catalogue of English proverbs, which are often warnings, especially warnings about hubris or risk-taking. Some of the better known examples that warn against getting carried away by some exciting new prospect are: 'All that glitters is not gold', 'Fools rush in where angels fear to tread', 'Look before you leap', 'Marry in haste, repent at leisure', 'The best-laid schemes of mice and men gang aft agley'.
The Bird in Hand was adopted as a pub name in England in the Middle Ages and many with this name still survive.
English migrants to America took the expression with them and 'bird in hand' must have been known there by 1734 as this was the year in which a small town in Pennsylvania was founded with that name.
Other languages and cultures have their own version of this proverb, notably the Czech 'Lepsi vrabec v hrsti nez holub na strese' (A sparrow in the fist is better than a pigeon on the roof.).
See also: the List of Proverbs.