Haydn Fox, assistant warden at RSPB Lakenheath Fen, explained the pairs mate for life and are extremely loyal to each other.
“We know they’re nesting when we start seeing single cranes out in flight,” he said.
“They’re just doing a change over on the eggs, so the other will go and feed, come back and relieve their partner of the duty.”
Fox said it had been hard not to get attached to the pairs at the site, near Lakenheath railway station and just off the River Little Ouse, which forms the border with Norfolk.
“They’re such majestic birds when they’re in flight, they’ve got their own personalities as well,” he said.
“We know the pairs really well here; you shouldn’t humanise them, but naturally we do… it’s lovely to see them all the time.”