It is "marvellous" to have otters and whistling ducks "right smack in the city", said National Development Minister Khaw Boon Wan in a blog post on Friday.
This comes after a pair of otters and a pair of lesser whistling ducks were sighted at the Gardens by the Bay.
Whistling ducks are rarely seen here, while the smooth-coated otters are of the same species as those that are now frequently seen in Pasir Ris Park. They were a native species but had not been seen "for decades", he said in a blog entry titled "Year of the Horse, Otters and Ducks at Marina Bay".
In the past 10 years, sightings of wild smooth-coated otters have soared. In 2000, just four sightings were reported. But by 2011, the number had risen to 39, according to figures from otter researcher Meryl Theng.
Referring to the sightings at the Gardens, Mr Khaw said these are possible only because "we keep our city clean and green" and this "collective effort" must be sustained.
The ducks were spotted breeding at the Gardens, and at last count, there were 11 ducklings.
He advised visitors not to disturb or scare them away, as they are still "camera shy".
On Thursday morning, another otter was spotted near the Marina Barrage. Most otters are sighted in Pasir Ris Park and the Sungei Buloh Wetland Reserve.