The Furious Firecrests are one of two rooftop guard varieties in the episode In the Air Tonight in Sly Cooper: Age of Thieves.
The Furious Firecrests wear white shirts and light blue suspenders, using a nail gun for their long-range weapon of choice. Seeing as they are specifically Common Firecrests, their feather and beak appearances reflect this greatly.
Where they lack in attack variety, the Furious Firecrests will chirp loudly to call for assistance if any other guards are present. They also have a fondness for long-range attacks, making them vulnerable up close.