Budgerigar

The budgerigar is a small, long-tailed, seed-eating parrot native to the drier parts of Australia, where it lives a nomadic life in flocks and breeds opportunistically. Wild birds are green and yellow with black scalloped markings on the nape, back and wings, while captive birds are bred in blues, whites, yellows and greys. Adults are told apart by cere colour and behaviour (Wikipedia, general species account).

It is a popular pet worldwide, and this is a non-native species that Wikipedia does not place in Sri Lanka; how it came to be on the Sri Lankan list should be checked. The 2012 National Red List gives no status under this name.