Bird experts have given a cautious welcome to the arrival of a male osprey at Wales' only nesting site.
There could be "fireworks" if two males clash over the nest
Staff at the Glaslyn site are "excited" - but also concerned the new arrival might clash with a male which has nested there for the past four years.
The regular male, and its mate, are expected to arrive in the next week.
Emyr Evans, RSPB osprey project manager at the site near Porthmadog, Gwynedd, said: "We expect fireworks. They fight in the air and dive bomb the nest."
"The male bird arrived around tea time on Monday and is on the nest this morning eating a mullet," he added.
"We have checked carefully and he is not ringed which means he is not the one who usually nests here, and he is not one of the chicks returning."
Whilst staff are pleased to have attracted a new osprey, they are now anxiously waiting to see if the regular male returns with its mate.
Mr Evans said: "They are what is called semi-colonial because they feed on fish so they do not have a territory, but they will fight for the nest.
"This one has been moving moss from the fields this morning and using it to refurbish the nest - it is typical behaviour of a bird taking over a nest."
He said two chicks raised in Porthmadog in 2005 could also be winging their way back to Wales this year, adding: "We think they were one hen and one cock, and we'll have to wait and see if they return."
Ospreys survive on a diet of fish and are most commonly seen in the UK in Scotland.
Around 56,000 people visited the centre, run by the Royal Society for the Protection of Birds, last year.