Graham Uney and his wife Olivia are leaving Canna for Shetland next month, blaming the owners, the National Trust for Scotland, for its poor management.
It means Canna will have seen its population fall from 22 in 2010 to just 12 when the Uneys go.
Mr Uney, who had worked as a gardener in Suffolk, was employed by the trust in the same role at Canna House. He said he had been excited by the prospect as it would give him an opportunity to indulge his interests of "studying all wildlife, including ringing birds for the British Trust for Ornithology, photography, hillwalking, and playing the mandolin and acoustic guitar".
Since arriving on Canna, whose population ranges in age from 15 to 80, in April Mr Uney has been posting a regular wildlife blog. However, his latest posting said: "The news is, we are leaving Canna in mid-October.
"Very frustrated with the management of the island, and upset to be leaving behind such a wonderful place, and some truly lovely people. Thanks to all our new friends on Canna for making the summer so special."
He also headed off any criticism that they weren't equal to Hebridean rigours: "Not suited to island life? Not at all. Off to Shetland. No jobs to go to as yet but we will be finding something soon, and in the meantime looking into various small business ideas."
The Uneys refused to make any further comment.
However, several of the other 10 people who have come and gone in the last few years have also criticised the trust's stewardship of the island, which was given to the organisation by celebrated Gaelic scholar and folklorist, the late John Lorne Campbell, in 1981.
Several have moved to other islands, citing the lack of long-term job security on Canna.
But Winnie MacKinnon, whose family have been on Canna since their forebears first arrived in the aftermath of Culloden in 1746, defended the trust. "People know what is expected of them when they come here," she said. "It is down in black and white. The main population of Canna backs the trust 100%. My family was born and bred on Canna, but I can tell you we wouldn't still be here if it wasn't for the trust."
A trust spokeswoman said "We regret this decision by the Uneys to move from Canna.
"Clearly there are many factors to consider in caring for a place like this, not least how the pressures and challenges of life on a small island can be addressed. The NTS is committed to working with the community to find the best way forward for Canna and its people."
She said the trust has invested significantly in Canna over the years to help make life there more sustainable – funding housing, water, electricity schemes, roads, the pier, a new vehicle bridge to the neighbouring island of Sanday, holiday accommodation and events.