A very easy species to sex visually.

Cocks have the entire face black. Be careful when buying young pairs as juvenile cocks will look like hens. Watch out for black spotting in the face.

There are two other very similar species to the Swee, considered by most to be sub-species of melanotis, but considered by some (myself included) to be separate species all together. The first is the Coccopygia bocargei. It also has the black face in cocks but there are two differences : the green on the back is finely barred as in the Common Waxbill, and the belly is butter-cup yellow. Not available in SA. It comes from western Angola an is also called the Angolan Swee.

The third species is the Coccopygia quartinia, commonly called the Tropical Swee or Yellow-bellied Waxbill. They come from East Africa

These are unfortunately very difficult to sex visually.

Hens have a slightly darker grey head, more noticeably around the cheeks but it is a very small difference.

The best thing to go on is the colour of the belly. In cocks the colour is more mustard with an orange ting (cocks left in both pics)

When Comparing the yellow-belly cock to the Swee cocks, the difference between them are obvious. The Swee has got the black face and the yellow-belly don't. Also the Swee is much bigger.

When you don't have two birds to compare the size note the yellow belly on quartinia against the grey belly of melanotis.

When Comparing the hens again the size difference is quite obvious if you have the luxury of comparison. If not note the more colourful belly of quartinia, although not as obvious as in the cocks.

The safest bet is to note the clearer white collar on melanotis which is not so distinct in quartinia.