(of animals, especially birds) to trim or dress (feathers, fur, etc.) with the beak or tongue: (Dictionary.com)
To dress (oneself) carefully or smartly; primp: (Dictionary.com)
To pride (oneself) on an achievement, personal quality, etc.: (Dictionary.com)
If a bird preens or preens itself, it cleans and arranges its feathers using its beak. (Cambridge Dictionary)
To spend time making yourself look attractive: (Cambridge Dictionary)
If someone preens themselves, they spend a lot of time making themselves look neat and attractive; used especially if you want to show that you disapprove of this behaviour or that you find it ridiculous and amusing. (Collins Dictionary)
Preening. How and why birds preen.
Why do birds preen themselves?