One of Europe's most endangered birds, Zino's petrel, has a slightly firmer grasp on survival than experts had previously thought.
By Alex Kirby
BBC News Online environment correspondent
Portuguese ornithologists have discovered a new breeding colony of the petrel in its mid-Atlantic fastness.
At great risk, but still there
They say this is significant because the petrel is the rarest bird to breed regularly in Europe.
But fears persist over its ability to avoid extinction for much longer.
The new colony, with 20 chicks and at least nine occupied nests, is the largest known. It was found on Pico do Areeiro, a peak in the central mountain massif of the Portuguese-administered island of Madeira.
The new nest site is some way from the three known colonies; access to it has been closed until scientists can be sure how many chicks there are and what risk visitors may pose.
Zino's petrel had been thought to number only 20-30 pairs, and is classed on the Red List compiled by IUCN-The World Conservation Union as critically endangered.
BirdLife International, a global alliance of conservation groups which works in more than 100 countries, says the species "continues to teeter on the brink of extinction".
Although there are hopes of finding more breeding colonies, the petrel is under constant threat from rats and semi-wild cats which take its eggs and chicks, and from human pressures.
It prefers to nest in burrows on ledges inaccessible to people, but goats and sheep which reach them can trample the vegetation, and they are no protection against predators.
BirdLife's Portuguese partner, Spea, is also concerned about the possible impact of a Nato radar station which Portugal is planning to build near the summit of Pico do Areeiro. It is lobbying for the station to be built elsewhere.
There are fears the fledglings could fly into the station's lights at night, and that radiation and construction work could both imperil the entire petrel population.
Zino's petrel is not in any case one of Nature's great survivors. In the last decade the colonies have averaged fewer than one fledgling per nest annually.