Rei

 Rei is Sakakibara's family pet bird that made its debut in episode 1.

Appearance
Rei is a small bird and has black eyes, orange beack and black feathers with a yellow spot under his eyes. In the manga, he has the same appearance.

Rei is a common hill myna ( http://en.wikipedia.org/wiki/Common_Hill_Myna ) sometimes spelled "mynah" and formerly simply known as Hill Myna, is the myna most commonly seen in aviculture.

Facts
Rei-chan saying "Ohayo Rei-chan", reminds that it's name is Rei, not another and repeats "Poor Reiko, poor Ritsuko " ( the words Ms. Mikami said at their funerals ). Reiko claimed the fact that she hates it (most likely because animals' memory can't be affected by the calamity and because it repeats those words).