Home to about 40 pairs of puffins around 80 years ago, the colony near Dancing Ledge in Purbeck has dwindled to just three pairs in recent times.
Although these birds have engaged in courtship behaviour, mating, and nest building in each of the last three years, and even feeding chicks in 2023, they have not raised any fledges in recent years.
The National Trust stepped up its investigation into the decline of the last colony in March, with motion-sensor trail cameras trying to establish why no chicks are surviving to fledge.
Having learned lessons from a similar venture in 2024, the trust used the latest solar-powered cameras housed in secure boxes on the cliff and angled to give better views into the nesting crevice.
The trust said this year it put better cameras in more specific locations, but because they are not live feed cameras, it will not know any more until it retrieves the cameras in late summer.
The project was led by marine ornithologist, Dr Richard Caldow, who has been monitoring the colony since 2023, helped by a team of volunteers from the Purbeck Natural History Forum.