Gannet

Gannets Temporal range: Early Miocene to recent
Northern gannets on Heligoland Northern Gannet calls: Grassholm, Wales
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
(unranked):	Aequornithes
Order:	Suliformes
Family:	Sulidae
Genus:	Morus Vieillot, 1816
Species
Morus bassanus Morus capensis Morus serrator
Synonyms
Moris

Nesting gannets (Morus serrator) at the Muriwai colony in New Zealand

Gannets are seabirds comprising the genus Morus, in the family Sulidae, closely related to boobies. They have a maximum lifespan of up to 35 years.^[1]

The gannets are large white birds with yellowish heads; black-tipped wings; and long bills. Northern gannets are the largest seabirds in the North Atlantic, with a wingspan of up to 2 metres (6.6 ft). The other two species occur in the temperate seas around southern Africa, southern Australia and New Zealand.

Gannets hunt fish by diving from a height into the sea and pursuing their prey underwater. Gannets have a number of adaptations which enable them to do this:

• no external nostrils, they are located inside the mouth instead;
• air sacs in the face and chest under the skin which act like bubble wrapping, cushioning the impact with the water;
• positioning of the eyes far enough forward on the face for binocular vision, allowing them to judge distances accurately.

Gannets can dive from a height of 30 metres (98 ft), achieving speeds of 100 kilometres per hour (62 mph) as they strike the water, enabling them to catch fish much deeper than most airborne birds.

The gannet's supposed capacity for eating large quantities of fish has led to "gannet" becoming a disapproving description of somebody who eats excessively, similar to "glutton".

Mating and nesting

A northern gannet in Bonaventure Island's colony

Gannet, Bempton Cliffs, Yorkshire

Gannets are colonial breeders on islands and coasts, normally laying one chalky, blue egg. It takes five years for gannets to reach maturity. First-year birds are completely black, and subsequent sub-adult plumages show increasing amounts of white.

The most important nesting ground for northern gannets is the United Kingdom with about two thirds of the world's population. These live mainly in Scotland, including the Shetland Isles. The rest of the world's population is divided between Canada, Ireland, Faroe Islands and Iceland, with small numbers in France (they are often seen in the Bay of Biscay), the Channel Islands, Norway and a single colony in Germany on Heligoland. The biggest northern gannet colony is in the Scottish islands of St Kilda; this colony alone comprises 20% of the entire world's population. Sulasgeir off the coast of the Isle of Lewis, Bass Rock in the Firth of Forth, Grassholm in Pembrokeshire, Sceilig Bheag, Ireland and Bonaventure Island, Quebec are also important northern gannet breeding sites.

Systematics and evolution

Gannet in the Celtic Sea – Ireland

The three gannet species are now usually placed in the genus Morus, Abbott's booby in Papasula, and the remaining boobies in Sula. However, some authorities believe that all nine sulid species should be considered congeneric, in Sula. At one time, the various gannet species were considered to be a single species.

• Northern gannet (also known as "solan goose"), Morus bassanus
• Cape gannet, Morus capensis
• Australasian gannet, Morus serrator

Most fossil gannets are from the Late Miocene or Pliocene, a time when the diversity of seabirds in general was much higher than today. It is not completely clear what caused the decline in species at the end of the Pleistocene; increased competition due to the spread of marine mammals may have played a role.

The genus Morus is much better documented in the fossil record than Sula, though the latter is more numerous today. The reasons are not clear; it might be that boobies were better-adapted or simply "lucky" to occur in the right places for dealing with the challenges of the Late Pliocene ecological change, or it could be that many more fossil boobies still await discovery. Notably, gannets are today restricted to temperate oceans while boobies are also found in tropical waters, whereas several of the prehistoric gannet species had a more equatorial distribution than their congeners of today.

Fossil species of gannets are:

• Morus loxostylus (Early Miocene of EC USA) – includes M. atlanticus
• Morus olsoni (Middle Miocene of Romania)
• Morus lompocanus (Lompoc Late Miocene of Lompoc, USA)
• Morus magnus (Late Miocene of California)
• Morus peruvianus (Pisco Late Miocene of Peru)
• Morus vagabundus (Temblor Late Miocene of California)
• Morus willetti (Late Miocene of California) – formerly in Sula
• Morus sp. (Temblor Late Miocene of Sharktooth Hill, US: Miller 1961) – possibly M. magnus
• Morus sp. 1 (Late Miocene/Early Pliocene of Lee Creek Mine, US)
• Morus sp. 2 (Late Miocene/Early Pliocene of Lee Creek Mine, US)
• Morus peninsularis (Early Pliocene)
• Morus recentior (Middle Pliocene of California, US)
• Morus reyanus – Del Rey gannet (Late Pleistocene of W US)

Cultural references

In many parts of the United Kingdom, the term "gannet" is used to refer to people who steadily eat vast quantities of food especially at public functions.^[2][3] But this characterisation, that implies that the birds feeding behaviour is one of grabbing all the available food, is not borne out by recent studies tracking gannet fishing patterns.^[4]

Young gannets were historically used as a food source, a tradition still practised in Ness, Scotland, where they are called "guga". Like examples of continued traditional whale harvesting the modern day hunting of gannet chicks results in great controversies as to whether it should continue to be afforded "exemption from the ordinary protection afforded to sea birds in UK and EU law".^[5][6]

References

• Miller, Loye (September–October 1961). "Birds from the Miocene of Sharktooth Hill, California" (PDF). The Condor 63 (5): 399–402. doi:10.2307/1365299. JSTOR 1365299. 

External links

Wikimedia Commons has media related to Morus (Aves).

• Live camera from Eldey Iceland
• Gannet videos on the Internet Bird Collection