Harblewheezer eggs have a curious protein lining inside the shell that serves to make the harblewheezer hatchling quite smelly and offensive to the taste of even the most indiscriminating of Ghanj-Rho's omnivores (that means amorphs). Thus, having a broken harblewheezer egg in your mouth would lead you to hurl pretty much involuntarily (assuming you were an amorph, which some readers have expressed a wish to be [and this phenomenon continues to baffle the sociology staff here at Schlock Mercenary]). Yuck.
It's interesting to note that the names for the various (we'll go ahead and call them) birds of Ghanj-Rho have the same sort of absurd, 'did-you-sound-that-out-before-writing-it-down' naming as birds elsewhere in the galaxy (hairy woodpecker, or tufted titmouse, anyone?). This is easily explained. The sort of people who go out of their way to spot birds and draw pictures of them in fieldbooks are just plain bent.