He joined staff, volunteeers, local supporters and representatives of funding organisations for an outdoor lunch in the new walled garden behind the Myers Farm visitors' centre.
Dr Ormerod is Professor of Ecology at Cardiff University's School of Biosciences and has been Chair of the RSPB's ruling Council since 2012.
But he was plain Steve Ormerod when he first visited Leighton Moss as a child, travelling to the reserve with his dad from their home in Burnley.
The Arnside and Silverdale area had always seemed a special place and still was today, he said. Leighton Moss was a jewel in the RSPB's crown and he was proud to celebrate the reserve's birthday as both RSPB Chair and as a Lancastrian.
After the speeches the RSPB's Chair cut a Golden 50th Anniversary Ribbon held at either end by the Reserve's two long-serving wardens: John Wilson (far right), now retired, and David Mower on the left of the picture, who retires this year after 27 years at Leighton Moss.
Guests at the lunch also had the opportunity to admire the ceramic art works made by pupils from local schools and used to decorate the walled garden.
Leah Sierpinski and Adam Lynch, both Year 10 pupils from Dallam School in Milnthorpe, were on hand to represent their school and the hard work and creativity that youngsters and their teachers had applied to the project.