How to identify the Blue-footed Booby

To correctly identify the Blue-footed Booby (Sula nebouxii), check each of these features. Birds can be tricky: habit, habitat, and call often confirm a sighting that a single photo cannot.

Size at a glance

Length

76-84 cm (30-33 in)

Wingspan

137-152 cm (54-60 in)

Weight

1.3-1.8 kg (2.9-4.0 lbs)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adults have a white head and neck streaked with light brown, a brown back and wings, and a white belly. The tail is dark brown. The most striking feature is their bright turquoise to deep blue feet.

2. 2

   Beak shape

   Shape and color of the bill: a key field mark.

   The beak is conical, pointed, and serrated along the edges, adapted for grasping slippery fish. It is typically grayish-blue or greenish-gray.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Pale yellow to yellowish-white, with a dark pupil. Males tend to have smaller pupils than females, giving their eyes a more intense yellow appearance.

4. 4

   Leg color

   Leg and foot color.

   Vivid blue, ranging from turquoise to deep azure.

5. 5

   Distinguishing features

   Standout features that separate this species.

   The bright blue feet are unmistakable. They also have a distinctive white patch at the base of the bill and a dark mask around the eyes.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   Juveniles have a duller, browner plumage overall, with less distinct streaking on the head and neck. Their feet are a duller, grayish-blue, not as vibrant as adults. The bill is also duller.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   No significant seasonal plumage changes. The intensity of the blue feet can vary with health, diet, and breeding condition, becoming brightest during courtship.

8. 8

   Sexual dimorphism

   How males and females differ.

   Females are slightly larger and heavier than males. Their pupils appear larger, giving their eyes a darker overall appearance. Males tend to have brighter blue feet, especially during courtship. Females also have a slightly different vocalization.

Key field marks

• Blue Feet. The most obvious and defining characteristic. Look for vibrant turquoise to deep blue webbed feet, especially prominent during courtship displays.
• Plumage Pattern. Observe the brown back and wings contrasting with a white belly. The head and neck are whitish with fine brown streaking.
• Eye Color and Mask. Note the pale yellow eyes with a dark mask around them. Males have smaller pupils, giving a more intense yellow appearance.
• Beak Color. The grayish-blue or greenish-gray conical bill is also a good identifier.
• Behavior (Plunge Diving). Watch for their characteristic high-altitude plunge dives into the ocean to catch fish.
• Courtship Dance. If observed during breeding season, the male's elaborate 'foot-waving' dance is unmistakable.

Explore the Blue-footed Booby