It's the first, and may be the only, calf seen in Warrnambool waters this season.

The pair were seen at the Logans Beach whale nursery yesterday morning before spending the afternoon basking Lady Bay.

But there was still plenty of action at Logans Beach with three other whales delighting onlookers with a splashy show of tails and fins.

Senior biodiversity officer for the Department of Sustainability and Environment, Mandy Watson, said the new mother had been regularly sighted at Logans Beach in the past few weeks.

"It's the only female that's been here almost every day the past month," she said.

"We have been watching her for so long, I was beginning to think she wasn't going to calf."

Ms Watson said she believed the female southern right gave birth on Wednesday.

"It's really exciting," she said of southern right calf.

"We don't really know a lot about (how and where they give birth), they seem to disappear towards the east and return with a calf."

Ms Watson said two calves had been spotted in the Portland area and one was seen further east but this was the first in Warrnambool this year.

She said it was possible the other mothers and calves in the area would travel to Logans Beach at some point during the season.