Most cormorants fly low over the water with their wingtips almost touching the surface at the end of the downstroke. They are taking advantage of “ground effect” – something that airplane pilots also have to account for.
Just after takeoff, an airplane seems to gain altitude easily. But by the time the plane is a wingspan distance off the ground (about 200 feet for a Boeing 747), the rate of climb will slow if no other change to control inputs have been made.
During landing, “ground effect” causes a plane that is less than a wingspan off the ground to appear to float and stop descending.
Both the takeoff and landing effects are caused by a reduction in induced drag because the ground interferes with the wingtip vortices.
Cormorants have discovered that by staying close to the surface of the water, drag is reduced and flight is more economical. Better economy means that less food is required and the chance of survival is increased.
LEARN MORE ABOUT CORMORANTS
KIDS QUESTION: In the museum exhibit, we asked: Why does the cormorant have a hooked beak?
The answer is: Because it eats fish and the hook makes it easier to catch them and stop them from escaping
Fish is the primary diet of the Double-crested Cormorant. A hooked beak makes it easier to prevent fish from escaping once they are caught. When a seagull, which does not have a hooked beak, catches a fish, it often struggles to actually eat the prey and stop it escaping.