Well, the word for bird, צִפּוֹר, forms its plural as צִפּוֹרִים birds. There is no and has never been a dual form #צִפּוֹרַ֫יִם#. There is a adjective צִפּוֹרִי birdlike with an plural צִפּוֹרִיִּים like in זֶה דִּינוֹזָאוּר בַּ֫עַל שְׁתֵּי רַגְלַ֫יִם וּמְאַפְיְנִים צִפּוֹרִיִּים this is a dinosaur with two legs and bird features. This word is also used in baby talk as צִפּוֹרִי birdy, so maybe you heard birds versus birdies in the same context.
Be sure to check the tips and notes (available only on the web version).