Cocos Booby or Blue-footed Booby?

Here's how to tell the difference

Cocos Booby image 1

Cocos Booby

Tap To compare
Blue-footed Booby image 1

Blue-footed Booby

Cocos Booby

Sula brewsteri

General Appearance

The Cocos Booby is a medium to large-sized seabird characterized by predominantly white plumage with a contrasting dark brown or blackish head, wings, and tail. This stark dichotomy in color gives the bird an unmistakable appearance in its natural environment. Its long, pointed wings and streamlined body assist in gliding over open waters with ease. The beak is relatively long and pointed, usually yellow in color, and adapts well to catching fish. The webbed feet are particularly suited for both swimming and perching on rocky surfaces.

Male vs Female

In the Cocos Booby, there is minimal sexual dimorphism, meaning males and females are visually similar. Both sexes exhibit the stark white and dark contrasting colors, and any size variation between them is typically negligible. However, during the breeding season, males may show slightly brighter colors around the beak and feet, which are thought to attract females.

Juvenile

Juvenile Cocos Boobies differ from adults in that they tend to have more uniformly brown plumage, which provides better camouflage against predators. As they mature, the white plumage develops gradually, and the dark areas become more pronounced, aligning with adult coloration. The younger birds also have duller colored beaks and feet compared to the vibrant hues seen in adults, which brightens as they age.

Size

26.0 - 33.9 in/37.0 - 57.1 oz

There's more to learn about Cocos Booby

View full details

How to tell the Cocos Booby from the Blue-footed Booby

Visual differences

The Cocos Booby (Sula brewsteri) and Blue-footed Booby (Sula nebouxii) differ visually in key areas. The Cocos Booby features uniformly white and brown plumage with duller juvenile hues, while the Blue-footed Booby has distinct blue feet and a stronger brown-and-white contrast as adults, with juveniles transitioning from gray feet. The Cocos Booby has a more uniformly colored beak, whereas the Blue-footed Booby's beak has a sheen. The two species are similar in size, with Cocos Booby ranging 26-34 inches long and Blue-footed Booby 25-35 inches, yet the latter is generally heavier (3.3 lbs) compared to the former (2.3-3.6 lbs).

Key differences and behavior

The Cocos Booby (Sula brewsteri) and Blue-footed Booby (Sula nebouxii) share impressive diving skills but differ in several behavioral aspects. Cocos Boobies perform a comical, high-stepping dance focusing on foot movements to attract mates, while Blue-footed Boobies use their striking blue feet in intricate courtship displays. The Cocos primarily inhabit remote tropical Pacific islands, preferring rocky cliffs, while Blue-footed Boobies favor arid coastal regions from California to Peru, often nesting on flat open ground. Both are monogamous, but the Cocos' preference for minimalistic nest sites contrasts with the Blue-footed's simple ground depressions. Their diets are similar, focusing on fish, though Blue-footed Boobies are more inclined towards anchovies and sardines. Neither species visits typical bird feeders, as both are oceanic hunters reliant on marine systems.

Cocos Booby vs [Select a bird]

Select a bird icon

[Select a bird]

Pick a bird to compare

Blue-footed Booby vs [Select a bird]

Select a bird icon

[Select a bird]

Pick a bird to compare