Learn Finnish: Lentävä pöllö palaa pesään. - The flying owl returns to the nest.

To form this participle, take the strong vowel stem of the verb lentää (to fly), which is lentä-, and add the participle ending -vä. The ending is -vä instead of -va because of vowel harmony. It functions just like an adjective describing the owl.

Why does the verb palata (to return) become palaa?

Palata is a type 4 verb. To get the present tense stem, you drop the -ta and add an a, giving you the stem palaa-. Normally, the third-person singular (he/she/it) ending doubles the final vowel. However, because Finnish spelling doesn't allow three identical vowels in a row, it simply stays as palaa.

Why is pesä (nest) written as pesään?

The verb palata involves movement towards a destination, so it requires a directional case. Here, the illative case (into) is used. We take pesä, lengthen the final vowel, and add -n to get pesään (into the nest).

Does the participle lentävä change if the grammatical case of the sentence changes?

Yes! Because active present participles act like adjectives, they must agree in case and number with the noun they modify. In this sentence, the owl is the subject (nominative), so lentävä is in its basic form. If the sentence was 'I look at the flying owl' (partitive), it would become Katson lentävää pöllöä.