"A bird in the hand is worth two in the bush."

A proverb of which one meaning is it is better to have something for sure (low risk) than something speculative (high risk). The paradox part is that investors will often not do a probability analysis for lowest risk/highest return. They will take their chances of getting something more speculatively than they will getting something less as a sure thing. It is well known that investors are risk averse: Given the opportunity to buy a new investment which has a 50% chance of returning twice the return on an existing investment the average investor will always keep the existing investment (in the example, each investment has the same average rate of return). However, investors will even keep "safe" investments when a riskier investment would on average return a greater profit. At the same time, people exhibit a herd mentality: If everyone else is buying a stock, then it must be a good buy. If everyone else is selling a stock it must be a bad stock. Contrarian investment strategies argue, correctly, that -- all other things being equal (a major caveat!) that one should buy when all others are selling an sell when all others are buying. The combination of these two facts -- the aversity of the average investor to risk and the tendancy to assume that the future will be like the past -- explains why most investors do not profit as much as they could from stocks and would really be better off investing in mutual funds a relatively safe investment with a better rate of return than bonds (one of the safest of investments ). Risk and potential reward are correlated (risky investments to attract capital must promise better return; safe investments are not under this pressure). The proverb reflects this -- and also the aversity to risk that most humans display. The two birds are of course objectively worth almost twice as much as the bird one has -- if you can catch them that is. The proverb is a warning to the imprudent and thus reinforces the irrational risk averse tendancy of most persons. A proverb (from the Latin proverbium) is a pithy saying which had gained credence through widespread or frequent use. ... Robert Boyles self-flowing flask fills itself in this diagram, but perpetual motion machines do not exist. ...

Due to the phrasing of the sentence (and the emphasis given to the position of the bird) it is plain that it is 'not a paradox' -- there is no counterfactual situation or logical impossibility created in this proverb.