Purple sunbird (male)

This tiny nectar-loving bird is a joy to behold. The non-breeding male and female are similar in colouration but the male has a blue-black stripe running down the throat. Over time blue dots appear and spread (second photo) till the bird is an iridescent, metallic blue-black all over. This is called the breeding plumage. The drab version is called the male's eclipse plumage.
The fourth photo is that of a female purple sunbird on a Hibiscus flower (Hibiscus rosa sinensis)...the lack of a vertical throat stripe is clear.