A bird in the hand is worth two in the bush
The proverb 'A bird in the hand is worth two in the bush' means it's better to have the certainty of a small thing than the possibility of something greater which may come to nothing.
Origin - the short version
'A bird in the hand is worth two in the bush' is one of the oldest and best-known proverbs in English and came into the language in the 15th century, probably imported from other cultures. 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 allusion may be to falconry where a bird in the hand (the falcon) was a valuable asset and certainly worth more than two in the bush (the prey).
This proverbial saying is first found in English in John Capgrave's The Life of St Katharine of Alexandria, 1450:
"It is more sekyr [certain] a byrd in your fest, Than to haue three in the sky a‐boue."
John Heywood's 1546 glossary A dialogue conteinyng the nomber in effect of all the prouerbes in the englishe tongue also includes a variant of the proverb:
Better one byrde in hande than ten in the wood.
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".
It's probable that Capgrave didn't coin the expression himself, but by how long the phrase pre-dates his publication isn't clear. The 7th century Aramaic Story of Ahikar has text that modern translations render as "Better is a sparrow held tight in the hand than a thousand birds flying about in the air.". Plutarch's Moralia has text that modern translations give as "He is a fool who leaves things close at hand to follow what is out of reach.".
While very similar proverbs existed in various cultures from antiquity there is no record of it existing in English in the form we now use before the 15th century. Although Heywood's book is later than Capgrave's it was by far the better known (due to Heywood's prominent position in the Tudor court) and it is Heywood who can be credited as the person who introduced it to the English-speaking world.
Variations of the proverb which don't mention birds existed in English prior to 1530, for example, this piece from Wycliffe's Bible, 1382:
Ecclesiastes IX - A living dog is better than a dead lion.
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 modern day European languages and cultures have their own version of this proverb:
In Czech - 'Lepsi vrabec v hrsti nez holub na strese'
(A sparrow in the fist is better than a pigeon on the roof.)
In German - 'Der Spatz in der Hand ist besser als die Taube auf dem Dach.'
(The sparrow in the hand is better than the dove on the roof.).
The close similarity of these suggests that one is a translation of the other. Which came first and whether either pre-dated the English version we can't now be sure.
See also: the List of Proverbs.