This is the 1981st most frequent Polish word.
dostrzegł
"Noticed" or "perceived."
In this sentence, 'dostrzegł' is used to indicate the act of perceiving something in a visual or metaphorical sense, signifying Arthur's noticing of the bird.
Artur dostrzegł ptaka na drzewie.
Arthur noticed a bird in the tree.
Here, 'dostrzegł' conveys recognizing someone's actions or contributions, in this case, noticing her effort.
Dostrzegł jej wysiłek, który włożyła w projekt.
He noticed her effort which she put into the project.
In this usage, 'dostrzegł' transfers into the mental acknowledgment of a concept or new understanding (realizing that the change was beneficial).