Eggs of elephant birds still reign supreme
Hard-shelled eggs were invented by birds and probably dinosaurs to protect offspring as they developed. Every organism basically has an egg, but the calcium carbonate of the bird's glandular secretion bestows great strength on this marvel we eat for breakfast. Just try breaking it with a plastic spoon! The largest known egg is to be sold in November at a much higher price than your chickens' version. In England, in Sussex, they have one of the very few treasures of the elephant bird Aepyornis sp.. These half ton, flightless monsters(3m or 10 feet in height), closest relatives of the kiwi, inspired Marco Polo and others to invent myths, but they died out 500 years ago, thanks to a few hungry sailors and predation by wild pigs.
This egg is a foot long (30cm) which makes it larger than dinosaur eggs. Better than that, no one has yet found any larger egg. Imagine how many small birds' eggs would fit that size - 12,000 is the maximum, but I could be wrong. Presumably the young needed to be large to survive in their natural habitat. Maybe they were camouflaged and looked after by the father for a short time, as in emus. £40,000 ($60,000) is the hoped-for price, while you could pick up one of our emu eggs here for nothing. The emu egg is roughly 13.4 by 8.9 cm (5.3 in × 3.5 in), just for comparison. We can only think that nobody except museums collects these birds' eggs, as schoolboys used to. The other rattite birds such as a kiwi or the flighted and quite large grey tinamou, Tinamus tao, from South America are often vulnerable or endangered so any collection would be totally unrealistic.
Madagascar is the ex-home of the elephant bird. The giant eggs are replicated in the related kiwi, which lays the largest egg for its size, and singly. I can only theorise that the Aepyornis species would lay single eggs, but at that size, it seems highly likely that the birds might even follow the kiwi pattern and mate for life, lay one egg and need several midwives- no I am JOKING now. What a shame that the actual bird and its colour can't be worked out, although the skeleton reminds me of a more upright giant moa - yet another extinction we could have done without! We have the moa listed among New Zealand extinctions here: - New Zealand Avian History.