Male-biased collision mortality of Whooping Cranes (Grus americana) in Florida may be associated with the tendency of males to lead flocks. The sex of Whooping Cranes was recorded for individuals leading flocks while flying and walking (n = 255). Males were more likely to lead than females both while walking and especially when flying. These observations support anecdotal reports that males tend to lead flocks. This flock behavior may partly explain male-biased mortality from collisions observed in Florida. Collision with power lines is the greatest known source of mortality for fledged Whooping Cranes. Our findings have implications for reintroductions and for the single existing self-sustaining population, which numbers > 250 individuals.