Prions are the most abundant birds in the Southern Ocean, occurring in countless millions. One reason for their success is the range of bill types they have evolved on the same basic body plan, which allows them to exploit a diversity of planktonic prey.
The group known as 'whalebirds' have a curtain of palatal lamellae along the sides of the birds' upper mandibles. Indeed, 'prion' comes from the Greek word for a saw, which refers to these saw-like structures. Whale birds use their large, muscular tongues to pump mouthfuls of water through the lamellae to strain tiny zooplankton.
Broad-billed Prions have 120 to 130 lamellae along each side of the upper mandible. Their large gular pouch can be distended, just like a baleen whale’s buccal cavity, to accommodate about four millilitres of water. This might not sound like much, but it represents about two per cent of their body mass, which is like a person holding 1.5 litres of water in their mouth. The water is pumped through the sides of the bill, trapping all animals larger than the 0.16-millimetre gap between successive lamellae.
Northern Fairy Prions (above, off Mercury Island, New Zealand) have more angular, well patterned heads than Subantarctic Fairy Prions (above right, off the Prince Edward Islands).
This story is from the {{IssueName}} edition of {{MagazineName}}.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber ? Sign In
This story is from the {{IssueName}} edition of {{MagazineName}}.
Start your 7-day Magzter GOLD free trial to access thousands of curated premium stories, and 9,000+ magazines and newspapers.
Already a subscriber? Sign In
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.
