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Nature

One Flight, Two Mediums.

Explanation of gannet hunting techniques and risks

Gannets courting
Gannets by Topi Pigula from Pixabay

Both beautiful and versatile the awesome Gannet.

I have always been amazed at how some birds can fly, dive into water, swim almost with almost equal dexterity, catch prey specifically designed to operate in its own medium and then surface with a its catch, often equal to a large percentage of the birds own body weight and then fly home.

Gannets are found in both the Northern and Southern Hemisphere. They typically live in large colonies with a constant landing and taking off on foraging trips. They fly up to 300 miles (480 km) in a day at a speed of roughly 45 mph (70 km/h).

This bird has some pretty cool features to be able to operate the way it does.

It can spot prey up to about 150 ft (45 m) above the water but would normally operate at 30 to 65 ft(10 m to 20 m). This is assisted by having its eyes far enough forward to allow binocular vision enabling better judgement of distance.

Our gannet typically dives into the water, folding its wings back and diving at up to 60 mph (100 km/h). Our gannet doesn’t have external nostrils, but internal. This ensures that it does not fill the nostrils with high pressurized salt water when entering the water.

Further to this our bird has a reinforced skull and sternum with air sacs under the skin in the face and chest which is a bit like bubble wrap and absorbs a lot of the entry shock.

The birds vision switches in a split second as it enters the water effectively blocking out ultraviolet light that distorts the position of fleeing prey.

Once underwater our gannet continues down to around 4 meters which effectively limits the fishes escape routes by cutting off the deep water one, being the most likely escape route. The school of fish would move even closer to the surface and get more concentrated with some jumping to try to escape.

At this point our gannet starts its underwater hunt swimming after the frightened fish. They are able to swim an additional 45 ft (15 m) underwater. They then swallow the fish underwater before surfacing to fly away.

In all this chaos, given that there are other predators and gannets are also stealing each others catches underwater. A Massey University study has found that some gannets had been killed when two birds dived for the same fish. The first one on target being the unfortunate one due to the second birds beak piercing the first birds neck. In addition there are also high speed impacts into either each other or into fast moving fish.

From the reproduction side gannets take about 5 years to reach full maturity. They pair for long periods but sometimes separate although separation is mostly when a partner dies.

gannets nesting
Gannets nesting. Photo by Yi Wei Sum ffrom Pixabay.

They lay a pale blue egg and both parents hatch and nurse the chick with the egg on top of their webbed feet to keep it warm. If a chick of less than 8 days old is lost the parents generally start again but beyond that they would wait for the next season.

Newly hatched chicks are black and eyes are closed at birth, after about 2 to 3 days the eyes open. Young birds are fed regurgitated fish and will fledge at around 100 days. the fledging process involved heading for a nearby cliff top and they could remain there for anything between 3 hours and 3 days before taking their first flight.

Gannet with fluffy baby
Gannet and chick. Photo by Nydegger René from Pixabay.

The juvenile bird will return to the colony from about three years old and breed at around 5 years.

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