Scramble for ostrich eggs (that take an hour to boil)

They take take almost an hour to boil and need soldiers the size of baguettes but ostrich eggs are flying off shelves at supermarkets as foodies bid to impress guests with the giant delicacy.

Waitrose supermarkets have seen a summer surge in sales of the eggs, which are the largest in the natural world and retail for £19.99 each in selected stores, where year-on-year sales have surged 16 per cent.

The eggs weigh in at 1.5kg and can be up to 42cm in circumference – the equivalent of about 24 large chicken eggs. Waitrose claims one ostrich egg can create an omelette big enough to feed 15 adults and that they make a hearty meal soft or hard boiled.

"Speciality eggs sales have had a cracking summer," said Waitrose's egg buyer, Frances Westerman. "Shoppers love the wow factor they bring to a summer picnic. Just think of the size of the scotch egg!"

The eggs are laid by South African black ostriches based on a farm in Lincolnshire. Craig Culley from the British Domesticated Ostrich Association (BDOA) said that the 159kg birds can be prolific layers, producing one egg every two days.

They do, however, only lay in warmer weather so the ostrich eggs have a limited season, from March to September. Waitrose first sold them in May 2008 and the success has led it to expand its range of "speciality eggs".

Others that are on sale at Waitrose include pheasant and rhea – a South American cousin of the ostrich – whose eggs are recommended as good for scrambling.

Ostriches, the largest birds in the world, were first introduced to the UK in the late 1980s. The BDOA said it was now unclear how many were being bred on farms throughout the country. Their possession is regulated under Dangerous Wild Animals Act.

Waitrose supermarket is also selling turkey eggs for the first time this year, which are selling out each week. Ostrich eggs, meanwhile, are said to taste exactly like hen's eggs.

But they still fall some way short of the largest known egg in the world, which was laid by a Giant Elephant Bird some 400 years ago and stands at 13in tall and 3ft in circumference.