וַֽיְהִי־עֶ֥רֶב וַֽיְהִי־בֹ֖קֶר י֥וֹם חֲמִישִֽׁי׃ (פ)
Così fu una sera, e fu una mattina; (cioè) un quinto giorno.
Radak on Genesis
והעוף ירב בארץ, the emphasis here is on the word הארץ, i.e. even though its origin is in the waters the birds will grow and generally behave more like land-based creatures.