The bird was first spotted on Saturday at Loch of the Lowes reserve near Dunkeld, which had already welcomed the return of its regular resident male osprey just over a week ago.
Osprey LM12, known locally as Laddie, has been the breeding male at the site for the past eight years.
Since 2015 he has been joined by the female LF15, or Lassie, and the pair have successfully fledged a total of ten chicks together.
Staff at the Scottish Wildlife Trust, which owns the reserve, have been eagerly awaiting Lassie’s arrival over the past few days, but she has not yet been seen.
But for now this new bird is attracting Laddie’s attention.
The young female, dubbed NC0, was ringed as a fledgling in the Highlands in 2016, but this is likely to be only the first or second time she has made the 5,000-mile flight back to Scotland.
She has been spending an increasing amount of time on the nest over the past day or so and LM12 has made several attempts to breed with her.
SWT’s Perthshire ranger Sara Rasmussen said: “LM12 and NC0 are still fairly unsure of each other.
“He has shown some defensive signs but there have also been attempts at mating.
“Birds can take time to build a relationship, and so far they aren’t sharing fish in the same way that established pairs do.
“There is still some chance that LF15 will return this week.
“If she does it will be very exciting to see what plays out, and whether she is able to reclaim her nest from NC0.”
There was further drama on Sunday afternoon when another osprey, thought to be a male, was caught on camera dive-bombing the nest at speed.
“This is a fantastic reminder that there are lots more ospreys around and they are jostling to find nests where they can breed,£ Ms Rasmussen added.
“At some points in previous years we’ve seen upwards of half a dozen birds over the nest at Lowes in a single day.”
Ospreys were extinct in the UK for much of the 20th century.
They began to recover in the 1960s, and now an estimated 300 pairs of ospreys breed here each summer.
Ospreys migrate to West Africa during winter, flying up to 270 miles a day.
LM12's previous mate was the legendary female called Lady, who returned to Loch of the Lowes for 24 years in a row.
She was considered a wildlife phenomenon, having produced a record-breaking 71 eggs and fledging 50 chicks in her lifetime.
She was the oldest known osprey when she was last seen in 2014, reaching an estimated age of 29.
Female ospreys usually live for an average of eight years and produce about 20 chicks in that time.
SWT’s osprey webcam allows nature-lovers across the globe to follow events as they happen.
The reserve and visitor centre are currently closed to the public due to the Covid-19 pandemic.