Sydney's Taronga Western Plains Zoo has celebrated the milestones of two of its rhino calves.

New South Wales (NSW) state Environment Minister Mark Speakman said the two calves whose species are endangered in the wild are progressing well at Taronga Western Plains Zoo.

"The zoo is now operating successful breeding programs for three of the five surviving species of rhinoceros in the world, namely the Black, Greater One-horned and White Rhinoceroses," Speakman said on Wednesday.

Dafari, a male Black Rhino turned one today, while Rajah, a male Greater One-horned Rhino will mark his six-month birthday on April 25.

Rajah was the first Greater One-horned Rhino calf to be born in Australia, which took over 15 years of planning from zoo staff.

NSW Acting Premier Troy Grant commended the dedication of the keepers and staff at Taronga Western Plains Zoo for their part in this landmark birth.

"Taronga's very successful rhino breeding program is one of the many attractions to the zoo which is a mainstay of regional tourism for the area," Grant said.

Taronga zoo was chosen by the International Rhino Foundation in 1992 to develop a conservation-breeding program for the Black Rhino.