There are 17 species of penguin in the world (or 16 or 18, depending which source you consult).
Penguins are generally extremely short-sighted on land, though they can see very well under water.
Antarctic researchers have made several significant contributions in recent years to our knowledge of penguin behaviour.
Two projects in particular have investigated reports that penguins fall over backwards when looking upwards at planes flying overhead.
In 1999, researchers found that flying a helicopter over baby penguins makes them flap their flippers or run away.
Two years later, a million-pound project proved that penguins do not fall over when aeroplanes fly overhead.
In between these two important results, scientists finally confirmed in December 2000 that waddling is the most efficient way for Emperor penguins to walk.
The most striking recent discovery about penguins, however, dates back to research published in 1998, and concerns female Adélie penguins in Antarctica selling sex in exchange for gifts of rocks.
In a paper entitled 'Female Adelie Penguins Acquire Nest Material from Extrapair Males After Engaging in Extrapair Copulations' in the journal Auk (vol. 115, number 2, pages 526-8), F.M. Hunter and L.S. Davis report the first known case of prostitution among birds.
Several female penguins were seen to mate with males who were not their usual partners in exchange for gifts of rocks which they then used as nesting material. Some birds even indulged in courtship behaviour, then took the rocks without mating.
One particularly flirty example was seen to take 62 rocks from one male without ever delivering on her apparent sexual promises.
Further vital information about penguins was reported in the journal Polar Biology in December 2003 when Victor Benno Meyer-Rochow and Jozsef Gal published a brief note entitled 'Pressures Produced When Penguins Pooh - Calculations on Avian Defaecation'.
As the authors point out: 'Chinstrap and Adélie penguins generate considerable pressures to propel their faeces away from the edge of the nest.'
To work out how much pressure, all you need to know is the density and viscosity of penguin pooh, the shape and height above the ground of the penguin's rear end, and how far away from the nest the penguin pooh lands.
'With all of these parameters measured, we calculated that fully grown penguins generate pressures of around 10kPa (77mm Hg) to expel watery material and 60kPa (450mm Hg) to expel material of higher viscosity similar to that of olive oil. The forces involved, lying well above those known for humans, are high, but do not lead to an energetically wasteful turbulent flow.'
Their concluding words point the direction for further research: 'Whether a bird chooses the direction into which it decides to expel its faeces, and what role the wind plays in this, remain unknown.'
FURTHER PENGUIN FACTS:
Penguins sleep more deeply in the afternoon than in the morning. This was discovered by a French researcher in 2002 who went round penguin colonies prodding sleeping penguins with a stick and seeing how many prods were necessary to wake them up at different times of day. His research showed that an average of five prods is enough in the morning, but nine are needed in the afternoon.
In February 2001, a baby penguin was treated for depression after it was found wandering the streets of Melbourne, Australia. Adélie penguins have pink feet; Gentoo penguins' feet are orange; but Gentoo penguins have pink excrement.
On 1 September 1988, the New York Health Department revealed that in the previous year they had treated 8,064 people for dog bites, 1,587 people bitten by other people, and one who'd been bitten by a penguin.
On 23 August 1997, Edinburgh Zoo reported that it had been using suncream on its penguins because the unusually hot weather had been causing the birds to moult. This left patches of bare skin that needed protection from the sun.