The world's oldest zoo has boasted with the hatching of two adorable king penguin twin chicks for the first time ever in its history.The two fluffy fur balls can be seen exploring the Polarium enclosure in a video shared by the Schoenbrunn Zoo, in the city of Vienna, Austria, on Thursday, September 24.Hyped over their hatching, zoo authorities revealed that this is the first time they have welcomed twin king penguin chicks ever since the first individuals were brought to the zoo in 1976.Zoo director Stephan Hering-Hagenbeck said in a statement: 'Breeding king penguins is still rarely successful in zoos.'We have successfully bred the second largest species of penguin many times, but until now there has only ever been one chick.'The fact that there are two this year is a huge success.'Hering-Hagenback revealed that the successful hatching comes after years of attempts to set up a homogenous king penguin (Aptenodytes patagonicus) colony at the zoo, as part of the EAZA Ex-situ Programme.Zoo representatives said that both chicks hatched over the summer, the first of which was on July 23, while the second was on August 25.Explaining that they were not easy to notice at first, head of department Folko Balfanz said: 'King penguins don't build nests, they carry the egg on their feet under a fold in their belly and incubate it that way.'After hatching, the chicks continue to be kept warm and well protected. During this time, they only occasionally look out from between their parents' feet.'Balfanz emphasised that the two offspring have grown quite a bit thanks to their parents' great care and currently feed on pre-digested fish.They will reportedly lose their dense downy coat during their first moult at around ten months old, after which they are expected to grow their first waterproof feathers and have a go at swimming.The species is the second-largest penguin on Earth, and is native mainly to islands located around Antarctica.It is listed as of 'least concern' on IUCN's Red List of Threatened Species.