Merlin

Northern Gannet Life History

Habitat

Habitat Oceans

Northern Gannets forage mainly in saltwater, though they occasionally pursue fish well into the brackish mouths of large rivers, and wandering individuals have turned up on rare occasions in the Great Lakes or other inland freshwater bodies. They largely avoid arctic and tropical waters, mostly spending their lives from the latitudes of eastern Canada to the Carolinas. A few gannets are regularly observed in Florida and the Gulf of Mexico. They are uncommon in very deep water, remaining instead over the continental shelf, where their main prey species are found. For nesting, they select cliff ledges at the edges of bays or oceans, especially places close to large concentrations of prey fish.

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Food

Food Fish

Northern Gannets eat almost exclusively fish, especially those that school (or “shoal”) near the surface. Favored prey species in North America include herring, mackerel, Atlantic saury, sandlance, capelin, smelt, pollack, menhaden. They also eat shrimp and squid. In the Old World, including Iceland, gannets also eat coalfish, whiting, cod, haddock, sandeel, sprat, and pilchard. Gannets catch fish by diving from significant height (often over 100 feet) at high speeds (up to 60 miles per hour). They dive as deeply as 72 feet and can maneuver and swim underwater using both wings and feet. Fish are seized with the bill either on the downward part of the dive or on the ascent. Gannets swallow small fish underwater or bring larger prey to the surface to manipulate it with the bill before swallowing the fish head first. Large gulls (and Great Skuas) often attend gatherings of gannets, hoping to pirate a meal. Gannets, along with gulls, often forage near fishing vessels and take discarded bycatch or dive into nets after captured fish.

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Nesting

Nest Placement

Nest Cliff

Northern Gannets nest at the edge of the sea, on rocky cliffs (often on islands or stacks), sometimes on flat ground or slopes. Most nests are on the windward side of a headland, which provides consistent updrafts that assist birds in takeoff and landing.

Nest Description

The nest is a compressed pedestal of grass, algae, feathers, and mud, held together with excrement. Males do most of the nest building, starting with a scrape and then carefully building up the sides. Gannets build in odd objects found at sea or near the nest site, among them many household items. Nests average about 12 inches across and normally stand 8 inches above the ground, but some have been measured over 40 inches tall.

Nesting Facts
Clutch Size:1 egg
Number of Broods:1 brood
Egg Length:3.0-3.3 in (7.65-8.43 cm)
Egg Width:1.9-2.0 in (4.83-5.09 cm)
Incubation Period:42-46 days
Nestling Period:82-99 days
Egg Description:

Pale blue or greenish.

Condition at Hatching:

Helpless with little down.

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Behavior

Behavior Aerial Dive (water)

Northern Gannets are monogamous and mate for life, very much like albatrosses. Pairs form, and renew their bonds, at the breeding colony, called a gannetry, which may contain thousands of pairs in close proximity to each other. Young birds also return to the colony in their second or third year, forming “clubs” of birds that rest together and begin to learn the local fishing routes. Males begin to claim a breeding site in a colony in their third or fourth year, shaking their head side to side frequently, biting the nest site itself, and stretching the neck toward females that show interest. Clashes between males over nest sites can be intense, with bills locked and much pushing at the cliff edge; injuries are not uncommon. Once partnered, male and female greet each other at the nest site each time they reunite, the males shaking the head, the females offering the nape for the male to nibble. They also engage in so-called “mutual fencing,” wherein they face each other, often touching, calling, shaking heads side to side as their bills clack together, bowing, and finally preening each other’s neck. Both parents care for and feed the young, taking turns on fishing excursions that may last several days. Both sexes defend the nest and chicks aggressively against other gannets, using threat displays such as jabbing with the bill. After breeding, they forage off Newfoundland, Nova Scotia, and in the Gulf of St. Lawrence before migrating southward. They spend the nonbreeding months at sea, or in large water bodies such as marine bays. They are usually in sizable flocks executing swift, spectacular dives to capture schooling fish.

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Conservation

Conservation Low Concern

Northern Gannet populations appear stable in North America. Partners in Flight estimates a global breeding population of 720,000 and rates the species a 10 out of 20 on the Continental Concern Score, indicating it is a species of low conservation concern. The North American Waterbird Conservation Plan puts the North American breeding population at about 155,000 birds. Like most seabirds, gannets are vulnerable to negative impacts on their marine habitat, including toxic contaminants (which often become concentrated in their prey species), plastic and other trash (which they might ingest or become entangled in), and fishing nets (both in active use and discarded). Overfishing of prey species presents a danger to gannets, but the effects of climate change on prey—both in their numbers and their locations—may have even more profound impacts. If prey move too far from gannet nesting areas, the birds cannot nest at that location, and alternate sites may not be available nearer their prey.

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Credits

Kushlan, J. A., M. J. Steinkamp, K. C. Parsons, J. Capp, M. A. Cruz, M. Coulter, I. Davidson, L. Dickson, N. Edelson, R. Elliott, R. M. Erwin, S. Hatch, S. Kress, R. Milko, S. Miller, K. Mills, R. Paul, R. Phillips, J. E. Saliva, W. Sydeman, J. Trapp, J. Wheeler and K. Wohl (2002). Waterbird conservation for the Americas: The North American waterbird conservation plan, version 1. Washington, DC, USA.

Lutmerding, J. A. and A. S. Love. Longevity records of North American birds. Version 2015.2. Patuxent Wildlife Research Center, Bird Banding Laboratory 2015.

Mowbray, Thomas B. (2002). Northern Gannet (Morus bassanus), version 2.0. In The Birds of North America (P. G. Rodewald, editor). Cornell Lab of Ornithology, Ithaca, New York, USA.

Nelson, J. B. (2002). The Atlantic Gannet. 2nd ed. Norfolk, U.K: Felix Books Ltd., Great Yarmouth.

Sibley, D. A. (2014). The Sibley Guide to Birds, second edition. Alfred A. Knopf, New York, USA.

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