Martin Bailey - a founder of the friends group and wildlife adviser - said the next 12 months was crucial to determine exactly how successful the project would turn out to be.
The Friends of the Anglesey Red Squirrel group has been working with the Red Squirrel Project and other organisations to study ways of helping protect endangered colonies of the red squirrel.
Efforts to increase numbers living at the Pentraeth forestry and trap "invading" grey squirrels have met with success.
Martin Bailey - a founder of the friends group and wildlife adviser - said the next 12 months was crucial to determine exactly how successful the project would turn out to be.
"We know the numbers have expanded from 20-30 squirrels in 1998 to between 70-100 and they are now starting to be seen in Wern y Wylan, which is a good sign," said Mr Bailey.
"We now need another year of data from the forests of Pentraeth to really see how well numbers are recovering and how the red squirrels have coped with food shortages."
The data will also help squirrel biologist Dr Craig Shuttleworth from the Red Squirrel Project to discover how beneficial the trapping of grey squirrels has been.
The BBC's Wild Wales presenter Iolo Williams is another supporter of the scheme and is among the guests at the event being held at Oriel Ynys Mon at Llangefni.
'Eliminated'
"This project has been very difficult, with 100 traps being checked morning and night," said Mr Williams.
"I would like nothing more to see the greys eliminated; I always see it as a tree rat.
"I am old enough to remember reds all over mid Wales and I think they are magnificent creatures."
Greys were brought to the UK from the United States by the Victorians and their numbers have steadily grown at the expense of red squirrels.
The American greys compete for food and carry a deadly virus which has meant that red squirrels - the inspiration for Beatrix Potter - have disappeared from many areas of the UK.