Photos shared by Essex Police show smashed windows and a taped off entrance at the Shooting Butts hide at RSPB Rainham Marshes.
Another photo shows broken glass littering the doorway, with overturned stools on the floor behind.
The hide has been shut to the public since it was targeted by vandals overnight on April 22, so that the RSPB can carry out “extensive” repair work.
READ MORE: RSPB Rainham Marshes vandalism forces bird hide closure
A spokesperson for the nature charity called the damage “significant” and urged anyone with information to contact Essex Police.
Thurrock MP Jen Craft said she was “devastated” to see the photos of the damage to the “much loved and used” nature reserve.
She added: “I was in contact with the RSPB last week and will be supporting Essex Police as they conduct investigations into this mindless vandalism.
“The police are appealing for information about this incident – if you have seen or heard anything that may be useful, please report this using the details shared below.”
Anyone with information can get in contact with Essex Police by calling 101 or using the live chat service on essex.police.uk, quoting crime reference number 42/54578/25.
