See the entire entry for ḥiwwār adj. white

BT Git 68b(29) :שדא ביה קלא שדייה : he threw a clod at it [i.e. the bird] (and) it dropped it [i.e. the šamir]

See the entire entry for šdy vb. to throw (away or down)

BT Git 68b(29) :אזל אייתי שמירא לאותוביה עלויה : (the bird) went (and) brought the šamir to place it upon it

See the entire entry for šāmīr, šāmīrā n.m. flint, adamant; stone-cutting worm