The Lonchura punctulata, a particular species of finch, is a passerine bird common in Tropical Asia and can be observed to feed on the grass seedheads in overgrown areas.
I have spotted them rather frequently along this stretch of Pasir Panjang Road and sometimes in HortPark's Nursery Holding Area vicinity, but I have not seen the less common White-Headed Munia (Lonchura maja), Chestnut Munia (Lonchura malacca) for years now. The last I saw them was at the former Punggol fields. before the development razed everything to the ground, when I was doing a project in NUS.