Imagine if it did just literally “stand up,” though!

足下から鳥が立つ
(Ashimoto kara tori ga tatsu;
“A bird takes flight at one’s feet”)

Definition:

An expression of startlement. Something happens suddenly close at hand, or someone abruptly begins doing an activity, especially if they’re rushing it. Like when a human is passing by and a bird lies low, but if the human comes too close then the bird will take its chances by bursting out and flying off – which in turn startles the person with the beating of its wings.

Breakdown:

We begin with compound noun 足下 (ashimoto), “underfoot” or “at one’s feet.” This is marked by the particle から (kara) as the start of some verb of motion. Next comes the particle が (ga) marking the noun 鳥 (tori), “bird,” as subject of the verb. And finally comes the verb itself, 立つ (tatsu), “to stand,” or in this case “to rise,” “to depart,” “to take flight” (as seen previously) in conclusive form.

Notes:

Ashimoto may also be written as 足元 or 足許 without any change in meaning or pronunciation. The final verb may also be replaced with 飛び立つ (tobitatsu), making the “flight” part explicit. The generic “bird” may also be replaced with 雉 (kiji), “pheasant” – which makes sense, given that the original image is probably of ground-nesting pheasants. In a slightly more distant variant, the bird taking flight may be entirely replaced with 竜が上がる (ryuu ga agaru), “a dragon rises,” or 煙が出る (kemuri ga deru), “smoke comes out.”

This is the あ (a) entry of the Kyoto iroha karuta set. It is attributed to a 1692 浮世草子 (ukiyozoushi) titled 『世間胸算用』 (Seken mune san’you), roughly “Off-the-cuff calculations about society.”

Example sentence:

「試験の残り時間は後10分だと告げると、思案に暮れていた生徒達が一斉にビクッとして、足下から鳥の群れが立つように必死に鉛筆を動かし始めた」

(“Shiken no nokori jikan wa ato juppun da to tsugeru to, shian ni kureteita seito-tachi ga issei ni bikutto shite, ashimoto kara tori no mure ga tatsu you ni hisshi ni enpitsu wo ugokashi hajimeta.”)

[“I announced that there were ten minutes remaining in the test. The students, who had been lost in thought, all gave a start at once like a flock of birds suddenly taking off from underfoot, and began writing desperately.”]