Earlier this year I took a trip to North Berwick to escape the noisy hub of Edinburgh, and discovered the amazing Bass Rock, the remains of an ancient volcano now home to over 150,00 Gannets during the summer months. I was to see this enormous gathering again, only from the Isle of May this time, and though I had grown accustomed to watching Gannets fishing in the bay in my hometown from a young age, the sheer number of these birds had me wondering how individuals coexist in such an immense colony.
Gannets can mostly be seen during the breeding season in the months between April and October, while some non-breeding individuals take up permanent residence on the coasts of the British Isles. Their look is distinctive, with an elongated and slender form and facial features outlined in black, ensuring it is unmistakable amidst a gathering of gulls. They are beautiful fishers to observe, circling the sky endlessly with a keen eye for underwater movements of prey before diving from heights around 20m into equal depths. From my naïve perspective when I was young, they appeared to make light work of it, slapping into the waters between fishermen’s boats, but this does not give credit to their capability to withstand these impacts that would kill many other birds.
I recall a fisherman once relaying to me the myth that such diving feats render the birds blind and consequently starved to death, without many years behind them. I call it a myth in absence of any evidence from the natural world, though such an assumption may have stemmed from the opaque look of the Gannet’s third eyelid, which protects the eye and enables a forceful dive. Funny that the bird’s clever adaptation itself could be mistaken for the lack of a coping mechanism. The Gannet is missing an external nostril which also enables these dives, as well as air sacs under the skin of their face and chest acting as cushioning from any internal damage when the bird hits the water’s surface.
One myth down, other discoveries are being made about the Gannet’s behaviour under water, once their diving spectacle has been enjoyed from above. Researchers have spent time mapping the exact patterns of fishing dives, from what I remember as a youngster observing the ratio of failed to successful dives of one individual, to the way in which much larger colonies can deal with the traffic of fellow underwater fishers en masse. They’ve discovered how the Gannet can switch its vision from the binocular precision it takes to spot a fish from above to the underwater pursuit of a target, using wing flaps to propel itself into a swimming chase of up to 42 seconds. Because of the depth they can dive down to, the Gannet can also manipulate the element of surprise by performing a V-shaped dive which enables the bird to target fish from below after the initial shock of the water being disturbed.
They’ve also found that, far from a myth, larger feeding groups often collide with one another under the water, accidentally or with the intention of stealing a fish from another’s beak, but with fatal consequences if a neck or head is pierced with the momentum behind the dive. Well, although adaptations are a ’plenty, no bird is perfect! Such research is discovering that there is much more skill to be found under the water’s surface, for this species and many other divers alike. With so much time spent foraging out of sight, it only makes sense to investigate such an important part of the species’ ecology.
The Gannet is currently amber listed under Birds of Conservation Concern and Dedications for UK Taxa, and could be endangered by coastal developments around the British Isles, such as offshore windfarms threatening to encroach on breeding and feeding territories. Surveying colonies such as the stronghold on Bass Rock proves a challenge for conservationists but despite concerns over possible disruptions to the Gannet’s life history, population numbers and breeding productivity have remained steady if not on the increase. I’d be extremely disappointed if I weren’t able to see these impressive sea birds thrive for years to come.
5,434 total views, 9 views today
Latest posts by Rosie Bowman (see all)
- Christmas and the Natural World - 14th December 2015
- The Gannet; myths and truths about this impressive diver. - 1st December 2015
- A summer spent with the Osprey. - 18th November 2015