Tengu Raven Form

You can shift into the form of a giant black raven.

Prerequisite: Tengu Wings, character level 7th, tengu.

Benefit: Once per day, you can take the form of a Large black bird resembling a raven, granting you a fly speed of 60 feet (good maneuverability), a +4 size bonus to your Strength, a –2 penalty to your Dexterity, and a +4 natural armor bonus. This spell-like ability otherwise functions as beast shape II with a caster level equal to your level.

Source: Advanced Race Guide