Wastrels are unintelligent birdlike creatures native to the Gray Waste, but also found in other Lower Planes and the Outlands. They look like shabby ravens with dingy colors streaking their black feathers. They appear to be suffering from some wasting disease.
The birds drain strength and vitality from those they encounter, leeching local flora and fauna of their energy. They are forced to migrate every 3-6 months to find new resources.
Planescape Monstrous Compendium Appendix II