וַיֹּ֣אמֶר אֱלֹהִ֔ים יִשְׁרְצ֣וּ הַמַּ֔יִם שֶׁ֖רֶץ נֶ֣פֶשׁ חַיָּ֑ה וְעוֹף֙ יְעוֹפֵ֣ף עַל־הָאָ֔רֶץ עַל־פְּנֵ֖י רְקִ֥יעַ הַשָּׁמָֽיִם׃
Und Gott sprach: Es wimmle das Wasser von wimmelnden lebenden Wesen, und der Vogel fliege über der Erde an der Ausdehnung des Himmels.
Rashi on Genesis
נפש חיה LIVING CREATURES — Creatures that shall have vitality.
Rashbam on Genesis
יעופף על הארץ, even though its creation originated from the waters, it would grow to maturity on earth.
Sforno on Genesis
יעופף על הארץ על פני רקיע השמים, in order to cleanse the air of the atmosphere for the benefit of the inhabitants of the earth from any excessive moisture in the air which had resulted through the creation of the rakia on the second “day.”