Possible Clues:

• Wise birds
• Birds making shrieks in the East End?
• Birds that are an anagram of 'slow'
• Hearts broken from wails in parliament?
• Nocturnal rat catchers
• Mail carriers in Rowling tales
• Real head-turners?
• Pride : lions : parliament : ___
• Nocturnal horned creatures
• 'Wise' ones