Brown Booby – Daredevil Cliff Divers

Photo courtesy from Costa Rica Guide

Brown Booby (Sula leucogaster)

Maximum Length: 80 centimeters
Maximum Weight: 1,300 grams
Frequency: Abundant, found in most Pacific Islands

Although this large seabird exhibits sexual dimorphism, both the male and the female has a dark brown upper body with contrasting white on the lower portion. The main difference between sexes is the size of the body where the female can grow up to 80 centimeters and weigh 1,300 grams while the males are smaller which can grow up to 70 centimeters and weighs at least a thousand grams. Both of their beaks are sharp with edges that are jagged. Their wings are short, tails are long and tapered and their feet are paddle-shaped like the ones you see in a duck.

Courtship and Mating

Photo courtesy from mg.birds.wildiaries.com

The pairing of brown boobies starts when the male does a frequent and consistent greeting ritual which sometimes may require an elaborate performance to get the females attention.

This initial partnership may include the pair simultaneously go to feeding by plunging down to the sea at high speed where it mainly feeds on fish and squid. You can often see a pair of brown booby flying together just above your liveaboard vessel. But despite their agile flying abilities, they are clumsy especially during takeoffs and landings. Lucky for us, its not the case for our commercial plane pilots. Or in the case of seafaring, our boat captains.

If a bonding is already established, their relationship is now escalated where a pair of Brown booby can remain together over several seasons which is a little less similar to humans. Or is it the other way around?

During mating season, you can see them in the high cliffs of Cocos Island where they usually converge in large aggregation. The nest are mostly located on top of existing vegetation or in broken eggshells from the previous season. Each single nest can bear up to 2 eggs that has a chalky blue color. Once hatched, their young has a white to grey feather which will eventually turn brown when they mature.

High-Speed Altitude Diving

Photo courtesy from Kauai Endangered Seabird Recovery Project

Since their favorite meal are submerged a couple of feet underwater, brown boobies needs to enter the water at high speed to ensure they will have a meal once they get back to surface. When a brown booby is hungry, it will leave the premises of the cliff, takeoff and hover above the water in search for food.

Once food is in target, they will make a sudden descent by tucking in their wings while entering the water at high speed catching their meal by surprise. This daredevil maneuver is manifested especially if the feast is being sponsored through a bait ball where a single dive can take in not just a single fish, but probably more than it can swallow. In some instances, it prefers to catch fish that are leaping out of the water.

Reference

Wikipedia: www.wikipedia.org

All About Birds: www.allaboutbirds.org

Audubon: www.audubon.org

About Tristan Paylado
Tristan is a marine biologist and a CMAS 2-Star Dive Instructor
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