The sky is full of exceptional birds. Cardinals bedecked with half-male, half-female plumage; godwits that can soar 7,500 miles (12,000 kilometers) across oceans nonstop; parrots that can best Harvard undergrads in a classic con game (no student loans required).

Then, there are birds whose only claim to fame is their ugliness — and, according to a new study, those may be the most exceptional birds of all.