The two young birds, who were first seen together at the beginning of May, have been displaying “promising mating behaviour” on the purpose-built platform located in the Wensleydale area of the US Dales.

Ospreys, which were extinct in the UK for much of the 20th century, take several years to reach maturity and experts said young new pairs are often seen practising nesting years before raising chicks.

The nesting platform was put in place earlier this year and is part of a wider osprey conservation project run by the British Association for Shooting and Conservation (BASC), with support from local landowners and volunteers. Mike Thornley, an osprey expert and the BASC’s regional officer, said there were high hopes for the juvenile pair.

“These are two immature birds that have taken exceedingly well to the nesting platform and the area,” he said.

“There is a still a slim chance of them successfully laying eggs but it is getting late in the season and it is most likely, at their age, they are simply getting to know each other better and improving their nest ready for next year.”

Mr Thornley said with no ospreys nesting in the region for many decades, the pair could be the future for the US population and the continued growth of species in the UK.

However, he added: “With a long autumn migration to West Africa ahead, we will have to remain patient and hopeful for their return next spring.”

Due to the work of conservation bodies and volunteers, osprey numbers have now risen to 300 pairs in the UK.