Mutawakkil Abbasi constructed a fort and put windows in it so
that the sun may enter it from the four sides. He also placed
numerous birds around, so that whenever he sat in the court the bird
sang in such a way that it was difficult to hear anyone speak.
However, whenever he imprisoned Imam Hadi (a.s.) in that
palace, the birds fell silent. Also, as long as the Imam remained
there, they remained silent and when he came out, the birds began to
recite.
Mutawakkil was also having some birds, which remained still
and did not move as long as the Imam remained there; but when Imam Hadi (a.s.) went away, they began to cackle
Isbaatul Wilayah (Part One) – Ayatullah AliNamazi Shahroodi (r.a.)