The NSW Environment Protection Authority is investigating after 23 magpies were found dead in Clarkes Road, Ramsgate.
The magpies were found dead on Thursday, November 12 along a short stretch at the western end of Clarkes Road towards Rocky Point Road.
A number of other birds were still alive were rescued by WIRES volunteers but have since died.
"There were neurological signs that the birds had been poisoned," NSW EPA director of regulatory operations - metropolitan, Giselle Howard said.
"The EPA has asked for lab results which are expected to take about two weeks," she said.
"This will confirm whether the birds have been poisoned and, if so, with what type of poison.
"But without evidence it is very hard to find a culprit.
"We are keen to send a call out to the community to contact us on our Environment Line if they have any information.
"Some people may notice something small or someone acting strangely in the street so call us if you have suspicions.
"This is important because if we get a tip-off in real time we can contact other agencies such as the council or the RSPCA for timely investigation.
"This is a very serious offence under multiple pieces of legislation," Ms Howard said.
"It is against the law to kill native wildlife and there are also strict laws under animal cruelty.
"While this type of incident is new for this area, it's not uncommon that it does happen.
"Any culprit must understand the gravity of the situation.
"We don't know how poison got into their system but magpies are meat-eaters so it could have been a bait which could also attack family pets or children in public areas."
Anyone with information should call the 24-hour Environment Line on 131 555.