SEXING JAVA SPARROWS
The sexes of Java Sparrows are regarded as being identical in appearance, however there are several reliable ways to distinguish males from females. Like most mannakin species, the male is the only sex that actually has a song and courtship display. The song is not that musical, again like other species of mannakins, the male Java Sparrow stretches his neck, and legs, standing in a more vertical position and utters a warbling, squeaky song, audible for some distance. The posture and and song are unmistakable and immediately identify an individual as a male. However don't confuse singing with calling. Both sexes chirp and call frequently, but only males sing. Many people unfamiliar with singing, observe Javas calling and frequently think their hen is a male. The song and display of the male is unmistakable and not at all like frequent calling. Unfortunately many Javas are sufficiently nervous in the presence of people that singing at a close, observable distance can be a rare sight. Once the birds are settled and if you are persistent in watching them, you will eventually catch the male in his song and display.
However perhaps the best method for instant sexing of Javas Sparrows is done by comparison of two or more birds. Without a doubt there are physical differences in male and female Javas. Notably, the size of the beak and the color of the beak are the key to readily sexing Javas. Male Javas have a larger, darker red beak than females. This is especially evident in mature birds. A side profile of a male Javas beak reveals that where the beak going the head, the base of the beak is larger and has a pronounce higher profile or ridge. In birds which are in breeding condition, this profile is so evident that the beak appears to be swollen and bulging at its base. By contrast, female Javas have slim, less red, more pink colored beaks. The female Javas has no pronounced "swollen" base to its beak and the profile from head to beak is slim and straight, with no ridge. Simply put, male Javas have bigger, redder beaks, female Javas have slim pink beaks. This is quite dramatic in adults but it can be quite tricky to determine young birds. Also, in adults the color of the fleshy eye ring can be used in conjunction with beak size. Male often have a dark red eye ring, females have a paler, pink eye ring. If you have a large number of Java Sparrows to pool from, sexing pairs is relatively easy, but if you have a small number of birds, only as the case is only 2 birds to look at, sexing is not so easy. There is a wide variation in Javas and I have certainly seen strains of Javas in which the females closely resembled males because they were in such good condition.
Beak Profile and color are the key to sexing Javas!