The only two breeding pairs in England are thought to be in Cornwall
A pair of choughs have successfully hatched eggs for a second year in West Cornwall.
The birds, which feature on the Cornish coat of arms, returned to the county in 2001 after a 50-year absence.
Volunteers are providing 24-hour cover to protect the nest at Penwith until the chicks fly the nest next month.
It is hoped the round-the-clock protection will deter egg thieves and ensure the nest is not disturbed by dogs and cliff walkers.
The exact number of chicks is not known, but the parents are said to be working hard to feed them.
The black-plumaged bird with red legs and a curving red beak is feature on the Cornish coat of arms alongside the miner and the fisherman.
It is often mentioned in Cornish legend and it is said King Arthur was transformed into a chough when he died - with the red feet and beak representing his violent, bloody end.
In the 19th Century there were more than 100 pairs in the county, but the chough vanished after its food source dried up because of a decline in cliff top grazing and the use of pesticides.
The birds feed mainly on soil-living insects and prefer short turf with a plentiful supply of dung.
The only other known breeding pair in England are on the Lizard peninsula.
The RSPB, Natural England, the National Trust and the Department for Environment, Food and Rural Affairs set up the Cornish Chough Project to protect the wild population and promote chough-friendly farming of the cliffs.