My trip to Bempton on Saturday prompted me to make the Gannet, Morus bassanus, Bird of the Week, but it’s a bird I’ve no good images of. But, thanks to the brilliant Creative Commons licensing, I’m using lovely images by Steve Sawyer and Alex Oxborough. Thanks to both for making their work available.
Gannets are tremendous hunters, with binocular vision to spot their prey. They glide over the waters, diving head-first into the water to spear fish. They can dive to 20 metres, and enter the water up to 80 miles per hour. This has led to an established fact that gannets have air-sacs in their face that cushions the impact, like a shock absorber. The only problem is, there’s no real source for this. In fact, researchers at the Percy Fitzpatrick Institute of African Ornithology have cast this idea in some doubt. By attaching data-loggers to Cape Gannets, they can provide all the facts and figures on what happens when a gannet hits the water. The resultant force of impact? Nearly zero. The Gannet is so streamlined that it needs no shock absorbers.
So why the air-sacs? One possibility is that it is an evolutionary relic. Today, Gannets are perfectly streamlined. But if their ancestors were not so elegant, the air-sacs may have served the shock-absorber purpose.
Another possibility is that, similar to Pelicans, the air-sacs help with floatation. It’s useful for a deep-diving bird to get back to the surface quickly so as not to risk drowning. The air-sacs may help here.
More research is needed to establish an answer.
Away from the brilliant technical evolutionary adaptations of Gannets, it is interesting how they have entered popular culture.
We call a person of prodigious eating habits “a gannet”. It’s not an unfair label. Gannets are pretty good at polishing off a food source, not just fish, but happily predating the chicks of other birds, even other gannets. Oddly though, other species can happily nest within a Gannet colony with rarely any trouble.
Gannets are no apex predator though, and they have been threatened themselves by human hunters. Gannet chicks, or guga, used to be hunted in the UK, until outlawed in 1954 by the Protection of Birds Act. However, on Ness on the Isle of Lewis, an exemption is in place and guga hunting is still part of the culture. I’m all for the preservation of cultures, though I’m unsure how I feel about the continued hunting habits of the Niseachs. It must be said, they use traditional methods and have a specific limit on their catch, so it’s likely to be sustainable.
What do you think about culturally-justified hunts?