FOUR teens are set to be charged over the brutal killing of a swan as experts take her egg for hatching.

The boys, all aged in their mid-teens, are all from the Moonee Ponds and Essendon areas.

A police spokeswoman said the teenagers were identified by witnesses and are in the process of being interviewed by police.

The swan was tortured and pelted with rocks in the shocking incident on Wednesday afternoon.

The nesting animal was found on a lake bank with an open wound to the head, before succumbing to its injuries.

A woman who arrived soon after the attack desperately tried to save the bird.

She held the bird's head above water, but the swan died in her arms.

News of the swan's suffering has caused outrage in the community and among animal activists.

The Melbourne Zoo has stepped in to house the swan's egg, as the remaining black male swan has barely moved from the nest since his mate was killed at Moonee Pond's Queen's Park. It is feared he will starve himself to protect the egg.

Moonee Valley City Council made the decision to transport the egg after consulting zoo experts.

Melbourne Zoo natural fauna curator Peter Courtney said the zoo has set up an incubator to house the egg to help the struggling male.

“It will try and ensure the survival of the young and we will raise it and we will release it back there once it is large enough to look after itself,” Mr Courtney said.

He said looking after the nest is normally a role shared by the two swans and the male on his own may not leave the nest for up to a week for fear the egg could be in danger.

“The solitary animal needs to get off and feed … the longer they have to be away, the more chance there is of the eggs becoming chilled and the embryo dying,” Mr Courtney said.

Executive Manager Environment and Lifestyle, Scott Widdicombe, said the swan will be monitored as it attends the nest.

“At this stage we are not sure how long it will take for the swan to leave the nest,” Mr Widdicombe said.

“Council is extremely concerned that it may be detrimental to the male swan to try and take the egg prematurely.”

Mayor of Moonee Valley, Cr John Sipek, said he was pleased the zoo had offered their assistance for the delicate case.

“The amount of community support for the plight of this swan and its egg has been heart-warming,” Cr Sipek said.

“If the egg is still in condition and viable we are hopeful that the zoo will do all it can to help achieve a good outcome.”Cr Sipek said he still couldn't understand the attack.

Originally published as Swan's egg rescued as teens quizzed