Thanks Todd

THE RIGHT WORD

ephemeral, evanescent, fleeting, temporary, transient, transitory

Things that don't last long are called temporary, which emphasizes a measurable but limited duration (: a temporary appointment as chief of staff).
Something that is fleeting passes almost instantaneously and cannot be caught or held (: a fleeting thought; a fleeting glimpse).
Transient also applies to something that lasts or stays only a short time (: transient house guests), while transitory refers to something that is destined to pass away or come to an end ( the transitory pleasure of eating).
Evanescent and ephemeral describe what is even more short-lived. Ephemeral literally means lasting for only a single day, but is often used to describe anything that is slight and perishable (: his fame was ephemeral). Evanescent is a more lyrical word for whatever vanishes almost as soon as it appears.
In other words, a job might be temporary, an emotion fleeting, a visitor transient, a woman's beauty transitory, and glory ephemeral, but the flash of a bird's wing across the sky would have to be called evanescent.