This refers either to 1) crows, a kind of bird that eats mostly grain, or 2) ravens, a kind of bird that eats the flesh of dead animals. Jesus's audience would have considered the ravens worthless since the Jewish people could not eat these types of birds.
This is an exclamation, not a question. Jesus emphasizes the fact that people are much more valuable to God then birds. (See: [[rc://en/ta/man/translate/figs-exclamations]])