Gannets are supremely adapted for plunge-diving. They lack external nostrils and have air sacs under their skin to cushion the impact of striking the water. The full force of the strike is further minimised by their streamlined body form, and miniature accelerometers attached to gannets reveal that there is little effect on the birds as they hit the water, allowing them to maintain their momentum beneath its surface. Indeed, gannets typically slow their descent when they reach their prey by flaring their wings and feet.
The depth to which gannets plunge depends on the speed at which they enter the water and this is related to the height from which they dive. When feeding on prey that is well below the sea surface, gannets climb to some 40 metres above the water and then rely on gravity to accelerate up to 90 kilometres an hour and penetrate the water almost vertically. However, they can also dive at shallow angles, speeding up by flapping until just before they enter the water, when they extend their necks and stretch their wings back to smoothly break the surface.
Denne historien er fra March/April 2022-utgaven av African Birdlife.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent ? Logg på
Denne historien er fra March/April 2022-utgaven av African Birdlife.
Start din 7-dagers gratis prøveperiode på Magzter GOLD for å få tilgang til tusenvis av utvalgte premiumhistorier og 9000+ magasiner og aviser.
Allerede abonnent? Logg på
EXPLORING NEW HORIZONS
Keith Barnes, co-author of the new Field Guide to Birds of Greater Southern Africa, chats about the long-neglected birding regions just north of the Kunene and Zambezi, getting back to watching birds and the vulture that changed his life.
footloose IN FYNBOS
The Walker Bay Diversity Trail is a leisurely hike with a multitude of flowers, feathers and flavours along the way.
Living forwards
How photographing birds helps me face adversity
CAPE crusade
The Cape Bird Club/City of Cape Town Birding Big Year Challenge
water & WINGS
WATER IS LIFE. As wildlife photographer Greg du Toit knows better than most.
winter wanderer
as summer becomes a memory in the south, the skies are a little quieter as the migrants have returned to the warming north. But one bird endemic to the southern African region takes its own little winter journey.
when perfect isn't enough
Egg signatures and forgeries in the cuckoo-drongo arms race
Southern SIGHTINGS
The late summer period naturally started quietening down after the midsummer excitement, but there were still some classy rarities on offer for birders all over the subregion. As always, none of the records included here have been adjudicated by any of the subregion's Rarities Committees.
flood impact on wetland birds
One of the features of a warming planet is increasingly erratic rainfall; years of drought followed by devastating floods. Fortunately, many waterbirds are pre-adapted to cope with such extremes, especially in southern Africa where they have evolved to exploit episodic rainfall events in semi-arid and arid regions. But how do waterbirds respond to floods in areas where rainfall - and access to water - is more predictable? Peter Ryan explores the consequences of recent floods on the birds of the Western Cape's Olifants River valley.
a star is born
It’s every producer’s dream to plan a wildlife television series and pick the right characters before filming.
