Ворона летела над дорогой и села на дерево.

the tree

Breakdown of Ворона летела над дорогой и села на дерево.

• и: and
• на: on
• дорога: the road

Questions & Answers about Ворона летела над дорогой и села на дерево.

Why do летела and села end in -а?

Because the subject, ворона (crow), is grammatically feminine.

In the past tense, Russian verbs agree with the subject in gender and number:

• masculine: летел
• feminine: летела
• neuter: летело
• plural: летели

So:

• ворона летела
• ворона села

both use the feminine past-tense form.

Why is it летела but села? Why not use the same kind of verb form for both?

This is a very common Russian pattern: the sentence mixes imperfective and perfective because the two actions are viewed differently.

• летела = was flying / flew as an ongoing action
  This is imperfective.
• села = landed / perched as a completed single event
  This is perfective.

So the idea is:

• the crow was in the middle of flying
• then it completed the action of landing

That is why this combination sounds natural.

If you said Ворона летела над дорогой и садилась на дерево, it would sound odd in most contexts, because садилась suggests an ongoing or repeated attempt to sit/land, not one finished landing.