How Do Pelicans Dive Without Getting Hurt? Plunge Diving

How a pelican dives

The brown pelican hunts by sight. It flies slowly over the sea, from a few meters up to about 20 m (65 ft) above the waves, watching for schools of small fish such as menhaden, anchovies and sardines near the surface. When it spots a target it tilts, partly folds its wings and drops.

As it falls, the pelican pulls its wings back along its body and stretches its neck and bill forward, forming a shape a little like an arrow. Just before it strikes the water, the bill opens. The two flexible halves of the lower jaw bow outward and the pouch balloons, scooping up fish together with a large gulp of water.

The force of the dive helps stun fish just below the surface. Because the bird is so buoyant, it usually goes down only a meter or two (3–6 ft) and bobs back up within seconds, facing into the wind, ready to drain its pouch.

What protects a pelican from the impact?

Hitting water at speed is like hitting a hard surface, so a diving pelican needs protection. Several features work together:

• Air sacs: pelicans have networks of air sacs beneath the skin of the chest and neck, connected to the respiratory system. They cushion the blow, like a built-in airbag, and also make the bird float like a cork.
• Light, air-filled bones: many of a pelican’s bones are hollow and filled with air, which keeps it light and helps it return to the surface quickly.
• Streamlined posture: with wings swept back and neck outstretched, the bird enters the water cleanly instead of belly-flopping.
• A twist on entry: brown pelicans are reported to rotate slightly to the left as they hit the water. This is thought to protect the windpipe and esophagus, which lie on the right side of the neck.
• Eye protection: like all birds, pelicans have a clear third eyelid, the nictitating membrane, which slides across the eye to shield it.

What happens after the dive?

Surfacing with a pouch full of water is only half the job. The pelican closes its bill, tips its head down to squeeze the water out through the sides, and then lifts its bill to swallow its catch. The pouch can hold around 11 liters (3 gallons) of water, so draining it takes a moment, as explained in How much can a pelican hold in its beak?

This pause gives thieves a chance. Laughing gulls and Heermann’s gulls often follow pelicans and sometimes stand on the pelican’s head to grab fish from the edge of the bill. Brown pelicans also scoop up fish while sitting on the water and sometimes take scraps near piers and fishing boats.

How good are pelicans at diving?

Diving is a skill that takes time to learn. Studies of brown pelicans have found that adults catch fish on a higher share of their dives than young birds, which have to learn the right height, angle and timing. In one study in Belize, adults succeeded on about four of every five dives, while young birds succeeded less than half the time.

This learning period is risky. Many young pelicans die in their first year, often because they cannot catch enough fish while they master the technique.

Which pelicans dive?

Of the world’s eight pelican species, only two hunt by plunge-diving: the brown pelican of the Atlantic, Gulf and Pacific coasts of the Americas, and the larger Peruvian pelican of the Pacific coast of Peru and Chile. Even the Peruvian pelican dives from lower heights than the brown pelican.

The other six species, including the American white, great white, Dalmatian and Australian pelicans, fish while swimming. They dip their bills into the water and often work in groups, forming a line or a horseshoe to drive fish into shallow water where they can scoop them up.

Other plunge-diving birds

Plunge diving has evolved in several groups of seabirds. Gannets and boobies dive from much greater heights than pelicans, up to about 30 m (100 ft), and hit the water at speeds of around 85 km/h (53 mph), protected by air sacs and a skull built to take the shock. Terns and kingfishers make shallower plunges to grab small fish, and ospreys dive feet-first to catch fish with their talons, as described in How do ospreys catch fish?

Myths and facts

Myth: pelicans eventually go blind from diving. This old story, often told at fishing piers, is not supported by evidence. Pelicans can be injured by fishing hooks and line, but there is no proof that repeated diving causes blindness.

Myth: pelicans dive deep after fish. Brown pelicans are too buoyant to chase fish underwater. They rely on the speed of the plunge to catch fish just below the surface.

Fact: diving is mostly done by brown pelicans. Seeing a pelican plunge from the sky is a sign you are watching a brown or Peruvian pelican, since other pelicans fish from the surface.