How to identify the Northern Gannet

To correctly identify the Northern Gannet (Morus bassanus), 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

87-100 cm (34-39 in)

Wingspan

165-180 cm (65-71 in)

Weight

2.3-3.6 kg (5.1-7.9 lb)

Physical features to check

1. 1

   Plumage

   Overall feather coloration and pattern.

   Adults are brilliant white with black primary flight feathers (wingtips). The head and nape acquire a yellowish wash, particularly pronounced during the breeding season. Juveniles are dark brown to black, heavily speckled with white, gradually becoming whiter over several years.

2. 2

   Beak shape

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

   Long, conical, and sharply pointed. Pale bluish-grey with dark cutting edges in adults. Juveniles have a darker bill.

3. 3

   Eye color

   Iris color and any distinctive eye markings.

   Pale blue with a dark ring around the pupil, giving a 'staring' appearance.

4. 4

   Leg color

   Leg and foot color.

   Dark grey to black, with greenish-yellow lines running down the front of the tarsus and toes, which are used in courtship displays.

5. 5

   Distinguishing features

   Standout features that separate this species.

   Large size, pure white body with black wingtips, yellowish head (adults), and powerful, direct flight. The unique plunge-diving behavior from considerable heights is also a key identifier.

6. 6

   Juvenile appearance

   How young birds differ from adults.

   First-year birds are entirely dark brown to black, heavily mottled with white spots and streaks, especially on the back and underparts. The bill is dark. Over the next 3-5 years, they gradually acquire adult plumage, becoming progressively whiter with each molt, retaining some dark mottling on the body and a dark tail until full maturity.

7. 7

   Seasonal changes

   Plumage variation between breeding and non-breeding seasons.

   The yellowish wash on the head and nape of adults is most prominent during the breeding season. Otherwise, adult plumage is largely consistent year-round.

8. 8

   Sexual dimorphism

   How males and females differ.

   Males and females are outwardly similar in plumage and size. There are no significant visual differences.

Key field marks

• Size and Shape. Very large, long-bodied seabird with long, pointed wings and a wedge-shaped tail. Appears powerful and streamlined in flight.
• Plumage (Adult). Brilliant white body, black wingtips (primaries), and a yellowish wash on the head/nape. Look for the pale blue eye with a dark ring.
• Plumage (Juvenile). Dark brown/black with white speckling, gradually becoming whiter over several years. Dark bill and tail.
• Flight. Strong, direct flight with steady wingbeats. Often glides on stiff wings. Can be seen soaring high above the water.
• Feeding Behavior. Distinctive plunge-diving from considerable heights (10-40m), folding wings back just before impact. This behavior is unmistakable.
• Bill. Long, conical, pale bluish-grey bill with dark cutting edges in adults.

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