The sound of a male bittern and the sighting of a possible female raises hopes for a future nest at Titchwell RSPB Reserve.
The male makes a booming sound that is described as being similar to someone blowing over the top of a half full bottle.
The sound has not been heard for two years at the reserve.
Warden Paul Eele said: “When I heard this bird I thought that’s a proper boom, which makes me think it is a new bird. t’s great to hear them again.”
The birds are secretive in nature and move silently by the waters edge where they live.
Mr Eele said: “I think it is because they are so secretive and hard to see people are always excited by seeing them and hearing them as they make such a weird sound.”
One of the heron family, they have pale brown feathers that are covered with dark streaks.
A second bird which is probably a female was recently sighted flying over the reserve.
The female takes care of the young by building the nest,sitting on the eggs and feeding the baby birds when they are hatched. Mr Eele said: “We definitely have a booming male but we don’t know if we have a nest yet.”
If there is a nest the female will be seen flying out to the water to collect fish which she will put into the young birds’ mouths. She could be spotted doing this any time from now till mid-July.