The phrase "field mouse ear" isn't a common phrase in English. It could imply the ear of a field mouse or be interpreted metaphorically.

खेत के चूहे का कान

English Usage: The field mouse ear twitched at the softest sound.

Hindi Usage: खेत चूहे का कान सबसे हल्की आवाज़ पर भी फड़क गया।