RSPB Rainham Marshes was targeted by vandals on April 22, who inflicted “significant” damage to the Shooting Butts hide.
The charity closed the hide to the public after the incident in order to carry out “extensive” repair work.
Photos shared on social media – which have since been removed – showed the windows smashed and the front entrance taped off.
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A spokesperson for the RSPB urged anyone with information to get in contact with Essex Police.
They told the Recorder: “Overnight on April 22, significant vandalism was carried out on the Shooting Butts Hide at RSPB Rainham Marshes.
“We are in contact with the police and urge anyone with any information to come forward to Essex Police.
“Shooting Butts Hide will be closed to the public until further notice as we carry out the extensive work that will need to be done to repair the damage.”
The other three hides at RSPB Rainham Marshes – the Purfleet hide, Ken Barrett hide and Marshland Discovery hide – remain open as normal.
Essex Police did not provide any information on the incident.
