Maybe something to use if the characters are stranded on the coast of the Black Kingdoms...
These (non-aerial) birds trampled on their prey until it was dead - surely a fearsome sight for PCs hiding and watching their black cannibalistic pursuers, just to see them attacked and trampled down by a gang of giant birds (I think REH describes a similar bird in "The Gods of Bal-Sagoth" - collected in Namelss Cults and in Black Stranger)
http://en.wikipedia.org/wiki/Terror_Birds
For German readers: http://www.spiegel.de/wissenschaft/erde/0,1518,365912,00.html
These (non-aerial) birds trampled on their prey until it was dead - surely a fearsome sight for PCs hiding and watching their black cannibalistic pursuers, just to see them attacked and trampled down by a gang of giant birds (I think REH describes a similar bird in "The Gods of Bal-Sagoth" - collected in Namelss Cults and in Black Stranger)
http://en.wikipedia.org/wiki/Terror_Birds
For German readers: http://www.spiegel.de/wissenschaft/erde/0,1518,365912,00.html