YOU SAID:

two birds sat on a window

INTO JAPANESE

二羽の鳥が窓に座っていた

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Two birds were sitting at the window

INTO JAPANESE

二羽の鳥が窓際に座っていた

BACK INTO ENGLISH

Two birds were sitting by the window

INTO JAPANESE

二羽の鳥が窓際に座っていた

BACK INTO ENGLISH

Two birds were sitting by the window