Tuesday, 15 June 2010
Last Weekend I had the pleasure of experiencing being marooned on an island with 170,000 birds! Lucky man male readers may think..... Sadly not it’s a colony of Gannets.
To anyone who has never had the pleasure, it’s an experience that is difficult to convey except it is an overwhelming assault on the senses, sight, sound and smell. Something that can only be achieved by visiting a major seabird colony.
The Bass Rock is the largest single island gannet colony in the world and described by Sir David Attenborough as “one of the Twelve Wildlife Wonders of the World”. It is home to an incredible 170,000 gannets at last estimate, the UK's largest seabird, and turns white from February to October when the gannets are in residence.
The Bass Rock is situated in the Firth of Forth, two miles east of North Berwick and one mile off the mainland, It is a huge trachyte plug rising 313 feet, with three sides of sheer cliff, and a tunnel piercing the rock to a depth of 105 metres, in other words it’s a big piece of volcanic rock sticking out of the ocean.
The Gannet is Britain's largest seabird with a wing span of just under two meters. When hunting for fish they slam into the sea like a living missile, descending at speeds of over 90 mph and diving to depths of 30 feet below sea level. The impact as it hits the water is so violent it can stun the fish, swallowing their prey whole before returning to the surface. The gannets are designed for high speed impact with more safety features than a modern vehicle. It has a skull like a crash helmet and its throat pouches swell like a driver’s air-bag as it crashes into the sea. The colony consumes 200 tons of fish every day and the birds can travel up to 540 kilometres or 330 miles in search of food. Gannets from the Bass have been satellite-tracked as far as Norwegian waters on hunting expeditions. One of the pairs has to remain on the nest while the other is searching for food. If the nest site is abandoned even for a short period another gannet will occupy their spot. It is not unusual for the bird to remain on the nest for 30 hours while their mate is searching for fish. The real fun comes when the birds return from their fishing trips. The gannet may be very graceful in the air and like a torpedo in water, but when it comes to landing on dry land think of it as a plane crash landing on an aircraft carrier. Time after time you hear a thud and see another gannet end up face in the dirt as it tries to land amongst the swathes of its kind. To make matter worse gannets are fiercely territorial and aggressive so crash landing on a neighbour can be an unpleasant and painful experience as the photos show.
The gannets lay their eggs within a comparatively short period, around the middle of May, when the newly hatched chicks weigh around 60g, but within 11-12 weeks, reared on the parents' catches of fish; they will have grown to an astonishing 4,500g. This early hatching and fast growth is to allow the young fledgling to be self sufficient by the time the autumn gales hit the Rock. In August and September the young gannets will tumble off the rock, hopefully learning to fly on the way down in this ultimate school of hard knocks. Three quarters of the young perish before reaching independence.
In October, most of them will travel south to the Mediterranean and many as far as the equator, to the Gulf of Guinea. The Gannets arrive back each year in January to re-establish their nesting territories on the cliff faces or on the rocky and grassy slopes of the island. Surprisingly, Gannets return each year to the same nest site to enable them to meet up with their mate of the previous year. The flat top of the island has fields of densely packed nests, about 3 per square meter, just beyond pecking distance, as Gannets are fiercely territorial and can be very aggressive to neighbours and even their mates. Gannets prefer windblown rocky stacks, as they allow the birds to make vertical takeoffs and landings. Any Gannet attempting to walk to its nest is battered by host of heavy dagger-like beaks from neighbouring birds.
The gannets use their head and beak to display various messages to others in the colony. When they lift their head upwards, known as 'Sky Pointing' accompanied by a curious strangled call, this displays a signal that they are about to fly off. Another posture is called 'Throat Gapping' when they open and close their beaks to warn of a predator; this display has a ripple effect throughout the colony as each bird passes on the message.
Home to a splendid array of seabirds the Bass Rock is well worth a boat trip out to see. Several boats sail out to the island from North Berwick including trips organised at the Scottish Seabird Centre. Guillemots, razorbills and parrot like puffins vie with shags, gulls and kittiwakes.
Lording it above them all is the majestic gannet.
These are Britain’s largest seabird and watching them plunge dive for fish is a truly unforgettable experience.