This is the 5211th most frequent Japanese word.
雄
"雄" means "male" (in animals) or "heroic/brave."
In this sentence, '雄' is used to describe the sex of the bird, meaning 'male'.
この鳥の雄は羽が鮮やかだ。
The male bird has vibrant feathers.
Here '雄' signifies the gender of the lion, indicating 'male'.
ライオンの雄は群れを守る役割がある。
The male lion has the role of protecting the pride.
In this example, '雄' is used to describe the male part of the plant, associated with reproduction.