A passer-by spotted the baby, believed to be a newborn, in Rough Wood Country Park off Hunts Lane in Willenhall at 1pm.
Officers confirmed the baby was dead as they launched an investigation into the circumstances of what exactly has happened.
Detective Inspector Wes Martin, from the force's CID, said: "This is a tragic investigation and our priority is to now find the baby boy’s mum to make sure she is ok.
"She may be in need of urgent medical attention and she is our absolute priority at the moment.
"We have been speaking to members of the public and would urge anyone with information to get in touch."
Police are currently examining the scene and are speaking to any potential witnesses. Anyone with information has been urged to contact them.
Officers also urged people not to speculate on the circumstances of the "distressing incident" as it hinders their investigation and is "upsetting" for those involved.
Anyone with information should contact the police via live chat on our website or call us on 101, quoting log number 1963 of May 20.
A spokesman for West Midlands Ambulance Service said: "We were called by police at 1:14pm to Rough Wood Country Park. We sent two ambulances, a paramedic officer and a critical care paramedic to the scene."
Rough Wood is a small nature reserve off Bentley Lane in Willenhall which The Wyrley and Essington Canal passes through.